2nd Symposium on Active nano/microsystems in the Spanish context

14 May 2026, 07:30 → 15 May 2026, 17:00 Europe/Madrid

Faculty of Chemistry / Enric Casassas, Aula Magna (Barcelona)

Maria Guix

Description

The development of active nano- and microsystems has attracted special interest both in the biomedical (e.g., drug delivery) and environmental (e.g., detection, remediation) fields. Their ability to be selectively functionalized and promote localized mixing at the micro/nanoscale accelerates reaction processes, as well as envisioning its use as advances sensing platforms. Research in this area spans from understanding the mechanisms behind their mobility, including the corresponding hydrodynamic studies and collective behavior, and reactivity to exploring their practical applications. 

This symposium focuses both on the fundament and applied studies around active microsystems, with the aim of fostering networking opportunities and collaboration within Spanish groups, as well as how to promote and pushing forward our research internationally. The multidisciplinary nature of active nano- and microsystems motors encompasses a wide range of expertise, requiring not only a deep understanding of material reactivity but also on the physical events related that promote their enhanced motion. In that regard, both chemistry, physics and engineering meets, and this is reflected in this Symposia, organized both by researchers at the Chemistry Faculty and Physics Faculty at the University of Barcelona. 

Key information

When?

14th - 15th May 2026

Where?

The symposium will take place at the University of Barcelona, in the Faculty of Chemistry and Physics, at the Aula Magna (sala Enric Casassas).

Why?
The goal of this symposium is to provide a platform for meaningful scientific exchange, fostering discussion and networking among researchers, particularly those working on active nano- and microsystems in Spain.

To whom is this directed?
This event is open to anyone with an interest in the field of active matter, whether you are an expert or simply curious about the latest interdisciplinary advancements in active nano- and microsystems.

How much does it cost?
There is no registration fee for this symposium.

What's including?
13/05/2026 (Afternoon):  Guided tour of the experimental labs working on nano- and microactive systems at both the Faculty of Chemistry and the Faculty of Physics. 
14/05/2026 (All day): Plenary and invited talks, as well as a poster session during the coffee break. With small surprise from the Nanoinventum program!
15/05/2026 (Morning): More plenary and invited talks, a second poster session, and a roundtable discussion to close the symposium and frame the future of the field in the Spanish context along with the CHARM-EU European University alliance. 

Do you have any questions?
Feel free to reach out to us at ames.symposium@ub.edu

Poster presentations

The abstract submission deadline for poster presentations has been set on 10/05/2026.

 

During the two-day symposium, there will be three dedicated poster sessions coinciding with the coffee breaks to encourage discussion and interaction among participants. If you submit a poster, you will be assigned to one of these sessions. Also, there will be a flash poster presentation just before to present selected poster. You will be notified if you poster has been selected and about your session allocation on 11/05/2026. The poster size for the event is A0 (841 mm x 1189 mm) and should be oriented vertically.

 

We are also excited to announce the following poster and flash talk awards selected by the organizing and scientific committee,

• Poster Award for Fundamental Research: Kindle + 1 sweatshirt
• Poster Award for Applied Research: Kindle + 1 sweatshirt
• Flash Talk Award for Fundamental Research: Kindle + 1 sweatshirt
• Flash Talk Award for Applied Research: Kindle + 1 sweatshirt

and a public choice award will be given to the best poster and best flash talk, consisting of a University of Barcelona thermo.

Lab Tours on the 13/05/2026

If you would like to participate in the lab tours taking place on the 13/05/2026 at the University of Barcelona, visiting different experimental labs working in active matter, you can register here. The tour will take place from 16:00-18:00. We will meet at the Atrium Solar from the Faculty of Physics and Chemistry of the University of Barcelona (check useful information section in the Indico webpage). 

Organizing Committee

• Dr. Julio Bastos-Arrieta
  Departament d’Enginyeria Química i Química Analítica, Institut de Recerca de l’Aigua
  (IdRA), Facultat de Química, Universitat de Barcelona
  
  
• Dr. Jordi Díaz Marcos
  Centres Científics i Tecnològics de la UB (CCiTUB), Institut de Nanociència i Nanotecnologia de la UB (IN2UB), Universitat de Barcelona 
  
  
• Dra. Maria Guix
  Departament de Química Física, Institute of Theoretical and Computational Chemistry (IQTC), Facultat de Química, Universitat de Barcelona
  
  
• Dr. Ignasi Pagonabarraga
  Departament de Física de la Matèria Condensada, Institute of Complex Systems (UBICS), Facultat de Física, Universitat de Barcelona
  
  
• Dr. Josep Puigmartí Luis
  Departament de Química Física, Institute of Theoretical and Computational Chemistry (IQTC), Facultat de Química, Universitat de Barcelona
  
  
• Dr. Juan Torres-Rincon
  Departament de Física Quàntica i Astrofísica, Institute of Cosmos Sciences (ICCUB), Facultat de Física, Universitat de Barcelona

Scientific Committee

• Joel Torres Andrés (Departament de Química Física, Facultat de Química, Universitat de Barcelona)
• Olga Bantysh (Departament de Química Física, Facultat de Química, Universitat de Barcelona)
• Marc Vergés Vilarrubia (Departament de Química Física, Facultat de Química, Universitat de Barcelona)
• Mario Palacios Corella (Departament de Química Física, Facultat de Química, Universitat de Barcelona)
• Aurora Guarducci (Departament de Química Física, Facultat de Química, Universitat de Barcelona)
• James Nicholas (Departament de Química Física, Facultat de Química, Universitat de Barcelona)
• Jing Huang (Departament d'Enginyeria Química i Química Analítica, Facultat de Química, Universitat de Barcelona)
• Alessandra Cutillo Foraster (Departament d'Enginyeria Química i Química Analítica, Facultat de Química, Universitat de Barcelona)
• Helena Massana (Departamento de Física de la Materia Condensada, Facultat de Física, Universitat de Barcelona)
• José Manuel Ruiz Franco (Departamento de Física de la Materia Condensada, Facultat de Física, Universitat de Barcelona)

Acknowledgements

We acknowledge the María de Maeztu Unit of Excellence 2021 CEX2021-001202-M. 

Special thanks to the support of projects PID2022-136709OB-C22 and PID2023-151682NA-I0 financed by MICIU/AEI/10.13039/501100011033 and by FEDER, EU.

 

 

Sponsors

• Facultat de Química de la Universitat de Barcelona
• Facultat de Física de la Universitat de Barcelona
• Institut de Recerca de l’Aigua (IdRA)
• Institut de Química Teòrica i Computacional (IQTC)
• Institut de Recerca en Sistemes Complexos de la Universitat de Barcelona (UBICS)
• Institut de Ciències del Cosmos (ICCUB)
• Secció territorial de la RSEQ
• Ajuntament de Barcelona

 

Organizers and collaborators

 

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Thursday, 14 May

08:30 → 09:00 Registration

09:00 → 09:30 Welcome

09:30 → 11:00 Invited Talks (I)

09:30 Bioinspired soft matter systems: from active colloids to synthetic cells

Cells, even in their simplest forms, exhibit adaptive motion and task execution, capabilities underpinned by their complex and hierarchized architecture, and their ability to dissipate energy. Replicating such intricate behavior at the microscale offers a pathway to uncover the fundamental physical and material ingredients required for biological complexity, while also inspiring the design of next-generation synthetic cells [1,2]. In this talk, I will present our approach to active and biomimetic soft matter across two complementary levels of complexity.

First, I will discuss simple active colloids as minimal model systems to design and control behavior in complex environments. We design active colloidal particles with tailored responses to external fields, enabling controlled motility and interactions. We then study how these programmed behaviors are modified by confinement, and crowding to uncover the physical mechanisms governing transport in porous media [3] and the emergence of collective dynamics [4]. Second, I will show how we move from rigid colloids to cell-inspired scaffolds based on giant unilamellar vesicles (GUVs). Compared with conventional active colloids, GUVs combine motility with membrane deformability, compartmentalization, making them particularly relevant as minimal cell models. I will present our recent results on motile GUVs driven out of equilibrium under external actuation, including run-and-tumble-like dynamics linked to membrane properties [5], as well as controlled deformations and division-like events under electric fields and light. Together, these results show how soft, adaptive compartments provide a route toward synthetic systems that not only move, but also display life-inspired shape changes and functions.

[1] G.Volpe, N. A. M. Araújo, M. Guix, M. Miodownik, N.Martin, L. Alvarez, et.al., Animated Matter Roadmap (2025)

[2] V. Willems, P. Moreno, J. Fojo, L. Rodriguez-Arco, L.Alvarez. Life-like processes in synthetic protocells under external fields. Newton (2026)

[3] A. Cazorla, M. L. Jiménez Olivares, R. Rica-Alarcón, C. Fernández-Rico, L. Alvarez. Field-programmed dynamical states control active microrod navigation in porous media. Submitted (2026)

[4] L. Alvarez, E. Sensé-Sansa, D. Levis, I. Pagonabarraga, L. Isa. Submitted (2026)

[5] V. Willems, A. Baron, D. A. Matoz-Fernandez, G. Wolfisberg, E. Dufresne, J. C. Baret, and L. Alvarez. Soft Matter (2025).

Speaker: Prof. Laura Alvarez (University of Bordeaux/ CNRS)

10:00 Programmable motion of magnetic nanobeads

Magnetic nanobeads, whose dimensions match those of biological agents, show great promise as wirelessly controlled microrobots in fluid environments. Particle tracking experiments reveal that their motion departs from classical diffusion, influenced by interrelated confinement, dipolar interactions, and temperature, affecting magnetic actuation. Our results underscore the challenges of achieving precise control under low-intensity magnetic fields, with responsiveness strongly modulated by particle size, magnetic moment, field strength, and effective temperature. These parameters collectively determine whether nanobeads exhibit enhanced diffusion, directional propulsion, or constrained motion. A central challenge remained in maintaining particles either independent or assembled into chains of tunable length, enabling more versatile magnetic steering and manipulation. To address this, we establish direct correlations between bead size, morphology, and field-dependent magnetic moment, offering a fundamental framework and a potential dataset for future machine learning approaches, for a magnetically actuated robotic control.

Speaker: Prof. Veronica Salgueiriño (Universidade de Vigo)

10:30 Mimicking biological emergent properties for biomaterial design

Living matter gets its function from soft interactions, multivalency, and constant exchange with the environment, operating far from equilibrium. By applying these principles to synthetic systems, we can create biomaterials that self-assemble, adapt, and respond in biologically inspired ways. This approach supports the development of polymersomes and similar nanoscale structures, whose behavior depends not only on their composition but also on their interactions across different scales. Importantly, such systems enable phenotypic targeting, where materials react to functional states instead of static molecular markers, and can move directionally through chemotaxis and phoresis, navigating gradients of chemical or physical cues. Embracing emergence as a design principle allows biomaterials to evolve from passive carriers to active, decision-making systems that engage with biology on its own terms.

Speaker: Giuseppe Battaglia (Institute for Bioengineering of Catalonia, Barcelona Institute of Science and Technology)

11:00 → 11:15 Pitch Presentations (I)

11:00 Large-Scale and Rapid Processing of 3D COFs via 3D-Controlled Reaction-Diffusion Zones

Three-dimensional Covalent Organic Frameworks (3D COFs) possess highly tunable porous structures that hold immense potential for advanced device applications. However, their integration into active nano- and microsystems is currently bottlenecked by conventional solvothermal synthesis methods. These traditional approaches require prolonged reaction times (>12 h) and typically yield unprocessable powders, preventing seamless device fabrication. To address the historical lack of preassembly mechanisms in 3D COF synthesis, we introduce a pioneering synthetic environment governed by precisely controlled diffusion. By eliminating turbulent mixing and fine-tuning the spatial reaction zone, we establish an unprecedented methodology that enables the rapid, one-pot synthesis of 3D COFs in under one minute. Crucially for active system integration, this diffusion-controlled approach directly yields self-standing 3D COF fibers on a centimeter scale. This breakthrough in material processability effectively bridges the gap between raw 3D COF synthesis and functional device manufacturing, offering a versatile, scalable pathway for their seamless integration and spatial patterning within next-generation nano- and microsystems.

Speaker: Anh Tuan Ngo (Departament de Química Física, Institute of Theoretical and Computational Chemistry (IQTC), Facultat de Química, Universitat de Barcelona)

11:05 Correlations in active nematic defects

In equilibrium statistical physics, the fluctuation-compressibility theorem states that the variance of the number of particles, in a region of space with size $R$ , scales as $σ_N∼R^d$, with d the spatial dimension. Active systems, however, often exhibit giant number fluctuations (GNF), where $σ_N∼R^d$, with $β>d$. In contrast, when $β We study an active nematic liquid crystal of microtubules at an oil/water interface, driven out of equilibrium by ATP-fueled kinesin–streptavidin complexes. In the active turbulent regime, the system continuously creates and annihilates ±1/2 topological defects. Previous results in our group showed that $β<2$ for the system of active defects, for values of R as large as the system size. The system of active defects is thus HU. Using both hydrodynamics and particle-based simulations, we unravel how defect-defect correlation and their creation/annihilation processes all conspire to result in this behavior (Hidden order in active nematic defects, PNAS, 2025).
Recent experiments, however, using larger active nematic cells allow accessing smaller $q$. In this regime, we observe that $S(q)$ does not vanish at the lowest accessible q, but that instead it decays and saturates to a finite non-zero value. This suggests a crossover from hyperuniform to uniform behavior beyond a characteristic length scale. Uniformity suggests that at sufficiently large length scales random noise, akin to thermal effects, dominates over activity-induced fluctuations. To assess this, we compare our results with those of electric charges in equilibrium, finding that the relation between partial structure factors in this system holds for active nematic defects, thus confirming the transition from HU to uniform behavior.

Speaker: Anna Monclús I Rojo (Universitat de Barcelona)

11:10 Sustainable Synthesis of MIL-53 (Fe): Integrating Life Cycle Assessment in Nanomaterials Early-Stage Development

Metal–organic frameworks (MOFs) are porous coordination polymers characterized by high surface areas and broad application potential, particularly in biomedicine. However, their conventional synthesis often relies on dangerous organic solvents such as N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA), and N,N-diethylformamide (DEF)[1, 2]. Among these materials, MIL-53 (Fe) was selected as a model system due to its typical dependence on DMF-based synthesis routes, which limits its sustainability and suitability for biomedical applications[3].
In this study, greener synthesis routes for MIL-53 (Fe) were investigated using aqueous systems incorporating different non-ionic surfactants, including Pluronic F68, Pluronic F127, and PVP K30. The choice of non-ionic surfactants was motivated by their comparatively lower environmental impact, being generally considered among the greenest classes of surfactants due to their lower toxicity, higher biodegradability, and reduced ecological footprint compared to the ionic alternatives. Experimental conditions were systematically varied by tuning surfactant concentration in solution, reaction temperature, and reaction time, alongside a comprehensive environmental evaluation. Life cycle assessment (LCA) was employed to quantify environmental impacts across the production process, providing a systematic framework for sustainability assessment[4].
Unlike conventional approaches, LCA was integrated during the experimental development stage rather than applied post-optimization, enabling iterative improvements while maintaining process flexibility. Selected synthesis methods were benchmarked against a conventional route to identify key environmental hotspots. The LCA model was developed using a cradle-to-gate system boundary and the Environmental Footprint 3.1 method. The results identified the washing steps as a major contributor to the overall environmental burden.
Overall, the hotspot analysis enabled the identification of critical process steps where targeted optimization can effectively reduce environmental impacts. Importantly, these improvements were achieved without compromising the properties of MIL-53 (Fe). These findings highlight the value of integrating LCA at early stages of MOF development to guide more sustainable synthesis design.

1. Annamalai, J., et al., Synthesis of various dimensional metal organic frameworks (MOFs) and their hybrid composites for emerging applications–a review. Chemosphere, 2022. 298: p. 134184.
2. Howarth, A.J., et al., Best practices for the synthesis, activation, and characterization of metal–organic frameworks. Chemistry of Materials, 2017. 29(1): p. 26–39.
3. Wang, B., et al., Ordered mesoporous metal-organic frameworks directed by amphiphilic block polymer as soft-template in N, N-dimethylformamide media. Journal of Colloid and Interface Science, 2025. 691: p. 137380.
4. Maklavany, D.M., et al., Eco-environmental analysis of different routes for the synthesis of MIL-53 (Fe): an integrated life cycle assessment and life cycle cost approaches. ACS Sustainable Chemistry & Engineering, 2023. 11(26): p. 9816–9832.

Speaker: Mehrafarin Hossein panah (University of Barcelona (UB), Department of Physical Chemistry, C / Martí i Franquès 1, 08028, Barcelona/ MOVIC WEARE SL, B72903347, Camino Mas De Clara S/N 43764, EL Catllar Tarragona Spain)

11:15 → 11:45 Coffee Break / Poster Session (I)

11:15 Biocompatible urease-powered nanomotors for targeted bladder cancer therapy

The effective delivery of anticancer drugs remains a critical clinical challenge due to factors such as degradation in biological environments, limited tumor penetration, and poor targeting of cancer cells. Specifically, in non-muscle invasive bladder cancer (NMIBC), the efficacy of intravesical therapies is further compromised by drug sedimentation and rapid elimination from the bladder via urination, leading to high recurrence rates and poor long-term survival in patients.
Urease-powered nanomotors (NMs), self-propelled nanoparticles that harness urea for autonomous motion, have emerged as a promising strategy to overcome these limitations. By utilizing the urea present in the bladder, these NMs can actively navigate toward tumor sites, enhance drug local retention, and improve drug delivery compared to standard therapies and passive particles. However, current NM designs often rely on inorganic materials and are loaded with conventional chemotherapies, underscoring the need for more biocompatible and personalized formulations.
Here, we introduce a novel formulation of urease-powered nanobots composed of poly(lactic-co-glycolic acid) (PLGA) loaded with a selective inhibitor of fibroblast growth factor receptor 3 (FGFR3), commonly altered in NMIBC. NMs were synthetized, loaded with FGFR3 inhibitor and functionalized with urease to enable self-propulsion in urea-rich environments. NM motility, cellular uptake, therapeutic efficacy and mechanisms of action were evaluated using NMIBC mice cells (MB49 cells). Finally, we performed in vivo experiments in which NMs were administered intravesical and survival and tumor volume were evaluated over 2 months.
Our results demonstrate that the NMs exhibit robust propulsion in the presence of urea and significantly enhanced cellular uptake compared to passive particles. In addition, drug delivery via NMs resulted in a 10-fold reduction in the IC₅₀ of free drug. In vitro studies revealed that the NMs induced S-phase cell cycle arrest and rapid apoptosis, consistent with the known mechanisms of FGFR3 inhibitor. In a murine model of bladder cancer, intravesical administration of the NMs led to effective tumor suppression, prevention of recurrence, and an 83% survival rate, with complete tumor eradication observed in treated animals.
Collectively, these findings demonstrate the potential of our biocompatible, urease-powered nanobots as an effective and targeted intravesical therapy platform for NMIBC.

Speaker: ines Macías Tarrío (IBEC)

11:15 Correlations in active nematic defects

In equilibrium statistical physics, the fluctuation-compressibility theorem states that the variance of the number of particles, in a region of space with size $R$ , scales as $σ_N∼R^d$, with d the spatial dimension. Active systems, however, often exhibit giant number fluctuations (GNF), where $σ_N∼R^d$, with $β>d$. In contrast, when $β We study an active nematic liquid crystal of microtubules at an oil/water interface, driven out of equilibrium by ATP-fueled kinesin–streptavidin complexes. In the active turbulent regime, the system continuously creates and annihilates ±1/2 topological defects. Previous results in our group showed that $β<2$ for the system of active defects, for values of R as large as the system size. The system of active defects is thus HU. Using both hydrodynamics and particle-based simulations, we unravel how defect-defect correlation and their creation/annihilation processes all conspire to result in this behavior (Hidden order in active nematic defects, PNAS, 2025).
Recent experiments, however, using larger active nematic cells allow accessing smaller $q$. In this regime, we observe that $S(q)$ does not vanish at the lowest accessible q, but that instead it decays and saturates to a finite non-zero value. This suggests a crossover from hyperuniform to uniform behavior beyond a characteristic length scale. Uniformity suggests that at sufficiently large length scales random noise, akin to thermal effects, dominates over activity-induced fluctuations. To assess this, we compare our results with those of electric charges in equilibrium, finding that the relation between partial structure factors in this system holds for active nematic defects, thus confirming the transition from HU to uniform behavior.

Speaker: Anna Monclús I Rojo (Universitat de Barcelona)

11:15 Fe-Coated Diatom Frustules via Electrodeposition: Preserving Porosity for Active Functional Systems

Diatom frustules are porous bio-derived silica microstructures with potential as active micro/nanosystems. However, their insulating nature prevents direct electrodeposition, limiting their functionalization with magnetic materials. Here, we introduce a conductive platform to enable iron electrodeposition onto frustules while preserving their native porosity. Polycarbonate membranes were first sputter-coated with a 100 nm Au layer, followed by frustule filtration and a second 20 nm Au coating to ensure electrical continuity. This configuration enabled conformal iron coating on the frustule surface. Optimized deposition conditions produced magnetic frustules while maintaining their hierarchical porous architecture, opening opportunities for magnetically driven microsystems, sensing, and catalytic applications.

Speaker: Carolina Ugarte Pereyra (UAB)

11:15 How Rotational Inertia Shapes Flocking

Collective motion is a hallmark of active systems, yet most models of flocking use overdamped dynamics with instantaneous alignment. In this work we investigate how introducing rotational inertia modifies the flocking transition using underdamped Langevin dynamics framework with torque-based alignment interaction. Compared to overdamped orientational dymanics where stronger alignment monotonically promotes order, we observe a reentrant loss of polar order with increasing alignment strength at intermediate inertia. This loss of order arises from underdamped rotational dynamics where overshooting leads to enhanced angular fluctuations that destabilize the collective motion.

Speaker: Shubhendu Shekhar Khali

11:15 Large-Scale and Rapid Processing of 3D COFs via 3D-Controlled Reaction-Diffusion Zones

Three-dimensional Covalent Organic Frameworks (3D COFs) possess highly tunable porous structures that hold immense potential for advanced device applications. However, their integration into active nano- and microsystems is currently bottlenecked by conventional solvothermal synthesis methods. These traditional approaches require prolonged reaction times (>12 h) and typically yield unprocessable powders, preventing seamless device fabrication. To address the historical lack of preassembly mechanisms in 3D COF synthesis, we introduce a pioneering synthetic environment governed by precisely controlled diffusion. By eliminating turbulent mixing and fine-tuning the spatial reaction zone, we establish an unprecedented methodology that enables the rapid, one-pot synthesis of 3D COFs in under one minute. Crucially for active system integration, this diffusion-controlled approach directly yields self-standing 3D COF fibers on a centimeter scale. This breakthrough in material processability effectively bridges the gap between raw 3D COF synthesis and functional device manufacturing, offering a versatile, scalable pathway for their seamless integration and spatial patterning within next-generation nano- and microsystems.

Speaker: Anh Tuan Ngo (Departament de Química Física, Institute of Theoretical and Computational Chemistry (IQTC), Facultat de Química, Universitat de Barcelona)

11:15 Many-body contributions to polymorphism and polyhexaticity in a water monolayer

Nanoconfined water plays a crucial role in nanofluidics, biology, and cutting-edge technologies. The process of melting water monolayers and quasi-two-dimensional confined water involves, as an intermediate stage, the hexatic phase—a state that lies between solid and liquid and is characterized by quasi-long-range orientational order and short-range translational order. However, the influence of hydrogen bond (HB) cooperativity in this process has not been thoroughly investigated. This gap hampers our understanding of the phase behavior of confined water and limits the accuracy of our models. To address this, we extend the water model developed by Franzese and Stanley, which explicitly includes many-body interactions (MBIs) of HBs. We distinguish the contributions of three-body and five-body HB-MBIs. Our Monte Carlo calculations in the isobaric–isothermal ensemble produce a detailed pressure–temperature phase diagram, revealing polymorphism and polyhexaticity: low-density square ice and high-density triangular ice are separated from the liquid phase by distinct hexatic phases. Three-body interactions notably promote crystallization and can destabilize the low-density hexatic phase, while cooperative five-body interactions help restore it, thus modifying the thermodynamic landscape. These findings demonstrate that HB-MBIs are key to determining the phase behavior of confined water, influencing phenomena such as non-monotonic specific heat, maximum-density lines, and the accessibility of the liquid–liquid critical point. Beyond advancing theoretical understanding, these results have wide-ranging implications for nanofluidics, interfacial science, and applications in biology, food technology, and pharmaceutics, where controlling water under confinement is essential.

Speaker: Oriol Vilanova (Universitat de Barcelona)

11:15 pH-Responsive Phospholipids Drives Active Self-Assembly of Vesicles for Controlled Release of Cargo

Stimuli-responsive supramolecular materials are smart materials whose molecular organization, and consequently their properties can be controlled using external triggers such as temperature, pH, and light. In recent years, significant efforts have been devoted into developing active liposomes with precisely controllable structural properties. These systems can be leveraged for the programmable transport and delivery of molecular cargoes, such as drugs, as well as for applications in synthetic biology. Among these, pH responsive vesicles are particularly attractive as they can respond to pH gradients that exist in biological environments. pH variations trigger changes in the designed constituent molecular units, leading to vesicle disassembly and cargo release. Despite considerable progress, active self-assembly of liposomes are rarely reported and active liposomes that are capable of programmable assembly-disassembly in response to stimuli are scarce. In this study, phospholipids are formed in-situ from simple molecular precursors and are made active through their pH responsiveness. The dynamic nature of imine bonds, makes the lipids and their vesicular assemblies responsive to pH changes in the environment. Since imine bonds are stable at neutral pH but dissociates under acidic conditions, lowering the pH leads to breakdown of vesicles and release of encapsulated molecules into the surroundings. By employing Gluconolactone, which slowly hydrolyzes into gluconic acid, a temporally programmable vesicle disassembly has been achieved. Notably, vesicle actively assemble and disassemble as the cycle can be repeated by switching the pH, establishing a key feature of responsive systems. Furthermore, the vesicles exhibit diameters of approximately 200 nm, placing them within the optimal size range for drug delivery applications. Combined with its pH responsiveness, this feature gives the minimal chemical design strong potential to develop pH responsive active drug delivery systems. In addition, this dynamic system closely mimics the adaptive behaviour of biological structures, providing a platform to better understand the operation of such complex mechanisms.

Speaker: Arshad Aranjiyil (Department of inorganic and organic chemistry, University of Barcelona)

11:15 Sustainable Synthesis of MIL-53 (Fe): Integrating Life Cycle Assessment in Nanomaterials Early-Stage Development

Metal–organic frameworks (MOFs) are porous coordination polymers characterized by high surface areas and broad application potential, particularly in biomedicine. However, their conventional synthesis often relies on dangerous organic solvents such as N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA), and N,N-diethylformamide (DEF)[1, 2]. Among these materials, MIL-53 (Fe) was selected as a model system due to its typical dependence on DMF-based synthesis routes, which limits its sustainability and suitability for biomedical applications[3].
In this study, greener synthesis routes for MIL-53 (Fe) were investigated using aqueous systems incorporating different non-ionic surfactants, including Pluronic F68, Pluronic F127, and PVP K30. The choice of non-ionic surfactants was motivated by their comparatively lower environmental impact, being generally considered among the greenest classes of surfactants due to their lower toxicity, higher biodegradability, and reduced ecological footprint compared to the ionic alternatives. Experimental conditions were systematically varied by tuning surfactant concentration in solution, reaction temperature, and reaction time, alongside a comprehensive environmental evaluation. Life cycle assessment (LCA) was employed to quantify environmental impacts across the production process, providing a systematic framework for sustainability assessment[4].
Unlike conventional approaches, LCA was integrated during the experimental development stage rather than applied post-optimization, enabling iterative improvements while maintaining process flexibility. Selected synthesis methods were benchmarked against a conventional route to identify key environmental hotspots. The LCA model was developed using a cradle-to-gate system boundary and the Environmental Footprint 3.1 method. The results identified the washing steps as a major contributor to the overall environmental burden.
Overall, the hotspot analysis enabled the identification of critical process steps where targeted optimization can effectively reduce environmental impacts. Importantly, these improvements were achieved without compromising the properties of MIL-53 (Fe). These findings highlight the value of integrating LCA at early stages of MOF development to guide more sustainable synthesis design.

1. Annamalai, J., et al., Synthesis of various dimensional metal organic frameworks (MOFs) and their hybrid composites for emerging applications–a review. Chemosphere, 2022. 298: p. 134184.
2. Howarth, A.J., et al., Best practices for the synthesis, activation, and characterization of metal–organic frameworks. Chemistry of Materials, 2017. 29(1): p. 26–39.
3. Wang, B., et al., Ordered mesoporous metal-organic frameworks directed by amphiphilic block polymer as soft-template in N, N-dimethylformamide media. Journal of Colloid and Interface Science, 2025. 691: p. 137380.
4. Maklavany, D.M., et al., Eco-environmental analysis of different routes for the synthesis of MIL-53 (Fe): an integrated life cycle assessment and life cycle cost approaches. ACS Sustainable Chemistry & Engineering, 2023. 11(26): p. 9816–9832.

Speaker: Mehrafarin Hossein panah (University of Barcelona (UB), Department of Physical Chemistry, C / Martí i Franquès 1, 08028, Barcelona/ MOVIC WEARE SL, B72903347, Camino Mas De Clara S/N 43764, EL Catllar Tarragona Spain)

11:45 → 12:15 NanoInventum

12:15 → 13:25 Invited Talks (II)

12:15 Template-Free Assembly of Nanoflowers into Actuatable Micropillars, Filaments and Magnetic Carpets with Tunable Reversibility

Magnetic nanoflowers (MNFs), characterized by high intrinsic magnetic losses and elevated specific absorption rates under clinically relevant alternating magnetic fields, represent promising candidates for magnetic hyperthermia applications [1]. In this work, we present a versatile and scalable platform for the fabrication of dynamic, field-responsive microstructures based on MNFs via a flexible, low-cost, and template-free self-assembly strategy. This approach is governed by tunable interparticle interactions, external magnetic fields, and spatial confinement [2].

By systematically controlling parameters such as ionic strength, particle surface charge, particle concentration, and interfacial coverage, MNFs spontaneously assemble in aqueous media into a wide range of architectures, including magnetic micropillars, microfilaments, and two-dimensional assemblies. Low ionic strength conditions promote reversible aggregation, whereas intermediate salt concentrations favor the formation of stable, irreversible structures. The resulting architectures exhibit tunable size, geometry, and dynamic behavior, enabling complex field-induced responses such as cilia-like oscillations, rotational motion, and torque-driven fragmentation of micropillars into swarming microfilaments.
Overall, this work establishes practical design principles for the template-free fabrication of biomimetic magnetic microarchitectures with controllable dimensionality (1D and 2D) and dynamic functionality, highlighting their potential in microfluidic systems and bio-microrobotic applications.

[1] García-Soriano, P. Milán-Rois, N. Lafuente-Gómez, C. Rodríguez-Díaz, C. Navío, Á. Somoza and G. Salas, «Multicore iron oxide nanoparticles for magnetic hyperthermia and combination therapy against cancer cells,» Journal of Colloid and Interface Science, 670, 73-85, 2024.
[2] Landi C, Pérez-Garrido R, Cuenca JM, Tajuelo J, Valeriani C, Gavilán H, Martínez-Pedrero F. Template-free fabrication of reconfigurable magnetic micropillars and filaments through controlled nanoflower assembly and actuation. J Colloid Interface Sci. 2026;140294.

Speaker: Fernando Martínez Pedrero (Universidad Complutense)

12:45 Spontaneous Emergence of Solitary Waves in Nonlinear and Active Flow Networks

Flow networks are fundamental for understanding systems such as animal and plant vasculature or power distribution grids. These networks can encode, transmit, and transform information embodied in the spatial and temporal distribution of their flows. We have explored flow networks that incorporate valves or elements exhibiting nonlinear relationships between flow rate and pressure drop. These elements act as interacting degrees of freedom, enabling the emergence of collective phenomena. We have shown that when such elements operate in a regime of negative differential resistance, the network can exhibit memory even at zero Reynolds number [1]. Increasing complexity gives rise to additional behaviors, including pattern formation, excitability, and self-sustained oscillations [2].
In this talk, we focus on a minimal yet physically grounded system that allows us to isolate the fundamental mechanisms by which active flow networks generate and regulate emergent dynamics capable of supporting information transmission. The system is composed of active units that pump fluid and elastic units that store volume. From first principles, we derive a discrete model—an active flow network—that enables the simulation of large systems with many interacting units. Numerically, we show that the pressure field can develop solitary waves, resulting in the spontaneous creation and transmission of localized packets of information stored in the physical properties of the flow. We characterize how these solitary waves emerge from disordered initial conditions in a one-dimensional network, and how their size and propagation speed depend on key system parameters. Finally, when the elastic units are coupled to their neighbors, the solitary waves exhibit even richer dynamics, with diverse shapes and finite lifetimes that display power-law behaviors that we can predict analytically [3].
Together, these results show how simple fluidic elements can collectively create, shape and transport information, laying the foundations for understanding—and ultimately engineering—information processing in nonlinear flow systems.
References:
[1] Martínez-Calvo, A., Biviano, M. D., Christensen, A. H., Katifori, E., Jensen, K. H., & Ruiz-García, M. (2024). Nature Communications, 15, 3121.
[2] Ruiz-García, M., & Katifori, E. (2021). Phys. Rev. E, 103, 062301.
[3] Fernández-Quevedo García, R., Cruz Antunes, G., Harting, J., Stark, H., Valeriani, C., Brandenbourger, M., Mazo, J. J., Malgaretti, P., & Ruiz-García, M. (2025). arXiv:2511.13448.

Speaker: Miguel Ruiz-Garcia (Universidad Complutense de Madrid)

13:05 Morphology-encoded dynamics of free inclusions in active nematics

Transport in active media has been extensively studied in bacterial suspensions, where tracers exhibit short-time superdiffusion followed by long-time diffusion, typically without a clearly resolved ballistic regime or an intrinsic length scale for optimal transport. In microtubule-based active nematics, research has mainly focused on controlling flows through confinement and boundary geometry. Only recently have freely moving rigid inclusions been investigated, mainly in confined settings where rotational motion is tuned via ratchet-shaped boundaries. However, their translational dynamics in unconfined active nematics remain largely unexplored.

Here, we experimentally investigate the motion of rigid polymer microdisks (30–300 μm in diameter) freely advected at the oil–water interface of a two-dimensional microtubule-based active nematic. Mean-squared displacement measurements reveal a clear crossover from a well-defined ballistic regime at short times to diffusion at long times, enabling direct extraction of propulsion speed, persistence time, and effective diffusivity. This crossover is strongly size-dependent: disks in the 50–100 μm range exhibit the highest propulsion speeds and diffusivities, together with the shortest crossover times, while smaller (30 μm) and larger (≥150 μm) disks show reduced propulsion and longer ballistic persistence before transitioning to the diffusive regime. Consequently, both propulsion speed and long-time diffusivity exhibit a pronounced non-monotonic dependence on disk diameter, peaking at ~75 μm. This characteristic size closely matches the intrinsic active nematic length scale, estimated from velocity correlation lengths (≈50–130 μm), revealing a direct coupling between inclusion size and the mesoscale structure of the active flow.

We extend this analysis to anisotropic inclusions, namely elliptical and crescent-shaped geometries. Anisotropy enhances transport: ellipses exhibit faster motion and higher diffusivity than circular disks, consistent with more efficient coupling to the spatiotemporal structure of the active nematic. In contrast, crescent-shaped inclusions display pronounced directional anisotropy, with motion along their long axis showing higher diffusivity and longer persistence than along the short axis. Together, these results demonstrate that both size and geometry act as effective control parameters for tuning transport in active nematics, providing design principles for directing motion in structured active materials.

Speaker: Xavier Arqué (ESPCI Paris)

13:25 → 15:00 Lunch

15:00 → 17:00 Invited Talks (III)

15:00 Supramolecular nano- and microchips for intracellular sensing and wireless actuation

Understanding and controlling how nanomaterials interact with living cells is key to advancing nanomedicine. Our work focuses on the design of chemically programmed, self-assembling supramolecular systems—ranging from hydrogels and nanoparticles to silicon-based microdevices—that can interface with cells to probe, track, and influence their behaviour. These versatile platforms open opportunities in biosensing, intracellular communication, targeted delivery, and the mechanical regulation of single cells.

In this talk, we will show how supramolecular chemistry provides a powerful toolkit to finely tailor the structure, properties, and functionality of nanostructured materials. We will present case studies including the surface modification of silicon microchips to enhance cellular internalization and enable real-time monitoring of intracellular glutathione levels. We will also introduce a self-assembling BODIPY-based scaffold engineered for mitochondrial targeting, with promising implications for bioimaging and therapeutic delivery. In addition, selected examples will highlight the integration of these systems into bioelectronic platforms, illustrating their potential to bridge biological processes with electronic readouts and control.

Speaker: Prof. Lluisa Perez-Garcia (Universitat de Barcelona)

15:30 Colloidal quasicrystals: How entropy can lead to forbidden symmetries

Quasicrystals are one of the most intriguing phases in classical matter. Defying the normal constraint of periodicity that applies to normal crystal structures, they can exhibit rotational symmetries that are forbidden for periodic crystals, e.g. 10-, 12-, 18-, 20-fold symmetries. These symmetries can be easily recognized in their diffraction patterns -- and it is this characteristic that led to their original discovery by Dan Shechtman in 1984. While quasicrystals were first found in atomic systems, they have since been found in a growing number of soft-matter systems, including nanoparticles, polymers, and micelles. How simple can a system be and still exhibit such an atypical, complex phase? Why does such a phase form in the first place? In this talk I will address these questions, and many others regarding the appearance of quasicrystals in soft matter. In particular, I will show how even a simple system of hard spheres can be designed to form quasicrystals. Using a combination of event driven molecular dynamics simulations and free energy calculations, I will discuss the huge importance of entropy in their stabilization, and end the talk by delving into the appearance of point defects in these systems.

Speaker: Laura Filion (Utrecht University)

16:00 Biohybrid Evolution: Plant-Inspired Machines for a Sustainable Planet

Among living organisms, plants offer a rich repertoire of biological strategies for interacting with complex and heterogeneous environments, shaped by millions of years of evolution across both terrestrial and aquatic habitats.

In this talk, we explore how key functional principles from plant biology can be translated into plant-inspired and biohybrid microfabricated systems, and how the development of these systems can, in turn, enable applications in sustainable agriculture and robotics. We present a new class of miniaturized, multifunctional plant-inspired machines designed for applications such as in situ environmental monitoring and targeted cargo delivery in confined and unstructured environments.

These systems combine bioinspired design with biohybrid approaches, integrating morphological and biomechanical features derived from both terrestrial and aquatic plants. Advanced fabrication techniques, including microcomputed tomography, two-photon lithography, and bioprinting, enable the development of scalable and sustainable prototypes. When tested in real-world settings (such as soil, leaf tissues, and aquatic environments), these systems exhibit plant-like strategies for actuation, attachment, and interaction with natural substrates.

Overall, this work demonstrates how plant biology can inform the design of adaptive systems for sustainable environments, while also providing a complementary experimental platform to investigate functional plant traits and ecosystem-relevant interactions, with implications for ecology, environmental restoration, and bioinspired engineering.

Speaker: Dr Isabella Fiorello (University of Freiburg)

16:30 Capillary aggregation and surface waves in bacterial colonies

Many bacteria inhabit hydrated environments like soil, textiles and agar hydrogels in the lab. In these environments, cells are surrounded by a water meniscus. First, I will show that the resulting capillary forces organize bacterial colonies, enabling cells to aggregate into densely packed nematic layers while still allowing them to slide past one another. Second, I will show that, when these bacterial colonies form thick multilayered films, they exhibit active surface waves. These results suggest that capillary forces may be a ubiquitous physical ingredient in shaping microbial communities in partially hydrated environments.

Speaker: Ricard Alert (Universitat de Barcelona)

17:00 → 17:15 Pitch Presentations (II)

17:00 Frictiotaxis underlies focal-adhesion-independent durotaxis

Cells can move directionally along gradients of substrate stiffness- a process called durotaxis. In most studied situations, durotaxis relies on cell-substrate focal adhesions to sense stiffness and transmit forces that drive directed motion. Until recently, it was not known whether and how durotaxis could take place in the absence of focal adhesions. However, our experimental collaborators showed that confined cells migrating with the amoeboid mode can migrate directionally up stiffness gradients, despite lacking focal adhesions. We proposed that the mechanism of this focal-adhesion-independent durotaxis is based on the fact that stiffer substrates offer higher friction. Additionally, we put forward a physical model that predicts that the cells polarise and migrate towards regions of higher friction- a process that we call frictiotaxis. Our collaborators then demonstrated frictiotaxis in experiments by showing that the cells can migrate up friction gradients even when stiffness is uniform. Overall, our results show a broader potential of durotaxis to guide cells that contact a substrate, and they reveal a new mode of directed migration based on friction. These findings have implications for cell migration during development, immune response and cancer progression, which usually takes place in confined environments that favour focal-adhesion-independent amoeboid migration.

Speaker: Peter Hampshire (Max Planck Institute for the Physics of Complex Systems)

17:05 Active Flows Control: From Isotropic to Anisotropic States with In-situ Generated Hydrogel Obstacles

Active matter refers to systems that consume energy from their surroundings, converting it into forces and motion, keeping them out of equilibrium and leading to diverse phenomena, from moving crowds to bacterial biofilms. This behaviour drives collective and stochastic dynamics, often linked to biological processes.
This study presents an active system with three components: an ATP reservoir, microtubules, and kinesin clusters walking along the microtubules. When brought to an oil-water interface, it forms a bidimensional active nematic material where "active turbulence" emerges due to chaotic flows.
Previous studies have presented a methodology for in-situ photopolymerizing fixed 3D hydrogel structures, enabling real time observation of the active material’s response. This approach has allowed for comprehensive studies of the material’s rheology, including shear viscosity and activity parameter quantification, as well as quantitative mapping of forces around topological defects.
In this work, we focus on how these embedded obstacles are capable of driving the material to transition from an isotropic state, where the flow characteristics are uniformly distributed in space, to an anisotropic regime. In particular, we aim to study and characterize a set of asymmetric structures that generate a net flow through an active pumping mechanism, as well as a network of symmetric structures that form a connected vortex lattice. The latter can give rise to a non-isotropic vortex distribution, with correlations that depend on the structure of the self-sustained flows.

Speaker: Marc Vergés Vilarrubia (Universitat de Barcelona)

17:10 Ionomer-Based Ion-Exchange Swimmers for Active Matter

Ion-exchange polymers offer a versatile platform for self-phoretic active colloids. Nafion, rich in sulfonic groups, generates strong ionic gradients and electric fields during counterion exchange when immersed in water, enabling autonomous fluid pumping and propulsion. Building on our earlier work with immobilized Nafion pumps, we now extend these concepts to fully motile colloidal swimmers. We fabricate asymmetric Nafion, metal hybrid micro- and nanoswimmers, typically Nafion rods capped with metals and metal oxides, using colloidal and stencil lithographic methods. In aqueous electrolytes, these structures display robust self-phoretic motion driven solely by ion exchange. Beyond individual propulsion, they exhibit diverse collective behaviours, including clustering, swarming, cooperative translation, and mobile pumping that draws in and concentrates surrounding material. We further show that wall zeta potential influences propulsion orientation, and collective patterns. Overall, Nafion-based ion-exchange micromachines provide a tunable polymeric model for studying self-phoretic propulsion, active-matter interactions, and emergent collective dynamics, with potential applications in pollutant capture and adaptive micro-/nanosystems.

Speaker: Maria Jose Esplandiu

17:15 → 17:45 Coffee Break / Poster Session (II)

17:15 Active Flows Control: From Isotropic to Anisotropic States with In-situ Generated Hydrogel Obstacles

Active matter refers to systems that consume energy from their surroundings, converting it into forces and motion, keeping them out of equilibrium and leading to diverse phenomena, from moving crowds to bacterial biofilms. This behaviour drives collective and stochastic dynamics, often linked to biological processes.
This study presents an active system with three components: an ATP reservoir, microtubules, and kinesin clusters walking along the microtubules. When brought to an oil-water interface, it forms a bidimensional active nematic material where "active turbulence" emerges due to chaotic flows.
Previous studies have presented a methodology for in-situ photopolymerizing fixed 3D hydrogel structures, enabling real time observation of the active material’s response. This approach has allowed for comprehensive studies of the material’s rheology, including shear viscosity and activity parameter quantification, as well as quantitative mapping of forces around topological defects.
In this work, we focus on how these embedded obstacles are capable of driving the material to transition from an isotropic state, where the flow characteristics are uniformly distributed in space, to an anisotropic regime. In particular, we aim to study and characterize a set of asymmetric structures that generate a net flow through an active pumping mechanism, as well as a network of symmetric structures that form a connected vortex lattice. The latter can give rise to a non-isotropic vortex distribution, with correlations that depend on the structure of the self-sustained flows.

Speaker: Marc Vergés Vilarrubia (Universitat de Barcelona)

17:15 Enhancing Human Skin Penetration with Biodegradable Enzymatic Nanomotors

The skin is the body’s primary biological barrier. Although essential for protection, this barrier function limits the efficacy of transdermal drug delivery, as most topically applied compounds fail to reach deeper skin layers at therapeutically relevant concentrations. Existing approaches often rely on physical disruption of the barrier, which can cause undesirable side effects. Moreover, many prior studies have been conducted in murine models, which do not accurately recapitulate human skin physiology, hindering the translation to humans. Here, we present an alternative approach using enzymatically powered nanomotors. We have developed organic biocompatible and degradable urease-powered nanomotors. We reconstructed native human skin architecture in vitro and confirmed the crossing capability of our nanomotors. Altogether, these results indicate that enzymatic nanomotors can cross human skin, through a combination of local modulation of the lipid structure and enhanced penetration driven by active motion, positioning them as a promising platform for transdermal drug delivery in humans.

Speaker: Carles Prado Morales

17:15 Frictiotaxis underlies focal-adhesion-independent durotaxis

Cells can move directionally along gradients of substrate stiffness- a process called durotaxis. In most studied situations, durotaxis relies on cell-substrate focal adhesions to sense stiffness and transmit forces that drive directed motion. Until recently, it was not known whether and how durotaxis could take place in the absence of focal adhesions. However, our experimental collaborators showed that confined cells migrating with the amoeboid mode can migrate directionally up stiffness gradients, despite lacking focal adhesions. We proposed that the mechanism of this focal-adhesion-independent durotaxis is based on the fact that stiffer substrates offer higher friction. Additionally, we put forward a physical model that predicts that the cells polarise and migrate towards regions of higher friction- a process that we call frictiotaxis. Our collaborators then demonstrated frictiotaxis in experiments by showing that the cells can migrate up friction gradients even when stiffness is uniform. Overall, our results show a broader potential of durotaxis to guide cells that contact a substrate, and they reveal a new mode of directed migration based on friction. These findings have implications for cell migration during development, immune response and cancer progression, which usually takes place in confined environments that favour focal-adhesion-independent amoeboid migration.

Speaker: Peter Hampshire (Max Planck Institute for the Physics of Complex Systems)

17:15 Influence of surface functionalization of silicon oxide microchips on cytocompatibilty and cellular internalization

Micrometric devices have attracted increasing attention for biomedical applications.[1] However, despite their biocompatibility and tunable surface chemistry, they often exhibit limited cellular uptake [2,3]. Self-assembled monolayers represent a reliable approach for modifying the surface chemistry of nano- and micromaterials. In this work, silicon oxide microchips (SiOµC) were functionalized with various silane derivatives to generate surfaces with different charge and wettability. Additionally, fluorescent labeling was added and enabled characterization and in vitro tracking.
Successful and stable modification was confirmed by water contact angle measurements and fluorescence imaging. Cytocompatibility was evaluated in HeLa and HaCaT cells, showing overall biocompatibility. Cellular association and internalization were assessed by flow cytometry and confocal microscopy. Positively charged SiOµC achieved the most efficient internalization, with up to 90% of HeLa cells containing internalized microchips at higher cell-to-chip ratios. These results highlight the critical role of surface chemistry in enabling cellular uptake of micrometer-sized silicon oxide microchips for biomedical applications.

ACKNOWLEDGMENTS
Project PID-2023-146658NB-C3 was funded by MCIN/AEI/10.13039/501100011033. We also thank AGAUR (Generalitat de Catalunya) for a grant to consolidated research groups 2021 SGR 01085.

REFERENCES
1. Janjua, T. I.; Cao, Y.; Kleitz, F.; Linden, M.; Yu, C.; Popat, A. Silica Nanoparticles: A Review of Their Safety and Current Strategies to Overcome Biological Barriers. Adv Drug Deliv Rev 2023, 203, 115115.
2. Bruce, G.; Bagherpour, S.; Duch, M.; Plaza, J. A.; Stolnik, S.; Pérez-García, L. Exploring the Influence of Silicon Oxide Microchips Shape on Cellular Uptake Using Imaging Flow Cytometry. Microchimica Acta 2024, 191, 554.
3. Bagherpour, S.; Vázquez, P.; Duch, M.; Pablo Agusil, J.; Plaza, J. A.; Redondo-Horcajo, M.; Suárez, T.; Pérez-García, L. Silicon Oxide Microchips Functionalized with Fluorescent Probes for Quantitative Real-Time Glutathione Sensing in Living Cells. J Mater Chem B 2024, 13, 1630-1642.

Speaker: Pascual López Algarra (Universitat de Barcelona)

17:15 Ionomer-Based Ion-Exchange Swimmers for Active Matter

Ion-exchange polymers offer a versatile platform for self-phoretic active colloids. Nafion, rich in sulfonic groups, generates strong ionic gradients and electric fields during counterion exchange when immersed in water, enabling autonomous fluid pumping and propulsion. Building on our earlier work with immobilized Nafion pumps, we now extend these concepts to fully motile colloidal swimmers. We fabricate asymmetric Nafion, metal hybrid micro- and nanoswimmers, typically Nafion rods capped with metals and metal oxides, using colloidal and stencil lithographic methods. In aqueous electrolytes, these structures display robust self-phoretic motion driven solely by ion exchange. Beyond individual propulsion, they exhibit diverse collective behaviours, including clustering, swarming, cooperative translation, and mobile pumping that draws in and concentrates surrounding material. We further show that wall zeta potential influences propulsion orientation, and collective patterns. Overall, Nafion-based ion-exchange micromachines provide a tunable polymeric model for studying self-phoretic propulsion, active-matter interactions, and emergent collective dynamics, with potential applications in pollutant capture and adaptive micro-/nanosystems.

Speaker: Maria Jose Esplandiu

17:15 Light-induced molecular motion in supramolecular fibres

Various synthetic stimuli-responsive microscopic systems with impressive control in relative molecular motion have been created [1] to imitate naturally occurring movement of biomolecules. Our group developed a purely supramolecular system where a molecular ‘traveller’ (TCPP) moved along gemini bis-imidazolium gelator fibers over several microns when irradiated with visible light in the presence of photoswitch (Azo) [2]. Real-time imaging of the motion in the solvated state was recorded using total internal reflection fluorescence (TIRF) microscopy.
In this work, we present a modified system with different azobenzene derivative (AzoF4) incorporated as a photoswitch. Because of higher cis:trans ratio, AzoF4 could change the extent of observed TCPP movement. Moreover, cis-isomer population can be easily replenished using visible light, allowing repeated energy release.

Acknowledgments
We thank the MICIU/AEI/10.13039/501100011033 for financing projects PID2021-123873NB-I00 and PID-2023-146658NB-C32 as well as the "Severo Ochoa" program for Centre of Excellence CEX2023-001263-S. We also thank the Agència de Gestió d’Ajuts Universitaris i de Recerca (AGAUR), Grant 2021SGR01085. DD thanks the predoctoral program AGAUR-FI ajuts (2024 FI-1 00769) Joan Oró.

REFERENCES
1. Baroncini, M; Silvi, S; Credi, A. “Photo- and Redox-Driven Artificial Molecular Motors,” Chem. Rev. 2020, 120, 200.
2. Samperi, M.; Bdiri, B.; Sleet, C. D.; Markus, R.; Mallia, A. R.; Pérez-García, L.; Amabilino, D. B. “Light-controlled micron-scale molecular motion,” Nat. Chem. 2021, 13, 1200.

Speakers: Daniela Dupkalová (Universitat de Barcelona), Aysha Fasna (Universitat de Barcelona)

17:15 Preventing clustering of active particles in microchannels

There is a growing tendency to confine motile microorganisms, such as bacteria, within narrow channels for the purpose of studying their chemotaxis, signaling, and interactions, or to model their motility in porous media. When the width of the channels is comparable to the size of the microorganisms, the free trajectories of two microswimmers can be significantly disrupted when they meet. A retardation occurs and clusters may form, which could limit the use and applicability of microfluidic devices. In this study, we present an expression for the maximum swimmer density that can be accommodated within a microchannel to avoid clustering. This expression depends on simple kinematic properties of single microswimmers and pairs of microswimmers at collisions that can be readily measured. The proposed methodology for measuring the required parameters is applied to the case of bacteria Bradyrhizobium diazoefficiens moving in long microchannels of cross section 1.8 μm × 1.8 μm. The advantage of this approach is that it does not necessitate the determination of an effective density-dependent speed, which is a requisite of the standard motility induced phase separation theory.

Speaker: Juan Pablo Carrillo-Mora (Universitat de Barcelona)

17:15 Synthesis and Characterization of Nano-Micro Composite Materials with Microwave Absorbing Properties

Radio-frequency (RF) and microwaves (MWs) are widely used owing to their benefits, including rapid transmission speed and broad frequency band. As a result,numerous applications in many different fields, including defense, telecommunications, healthcare, and consumer electronics have emerged.

This work focuses on the synthesis of magnetic functional materials embedded in a polymeric matrix for microwave absorbing purposes. These composite materials are developed for applications in reducing interferences by electromagnetic pollution and mitigating risks to both health and the environment.

The selected materials acting as the functional phase were Fe, Fe3O4, BaFe12-xCuxO19 and CoFe2O4, all in powder form. The synthesis routes used were Coprecipitation and Sol-Gel as wet-chemical methods provide excellent control in particle size and morphology, operating at low temperatures and low-cost. As the polymeric matrix, epoxy resin with specific additives was used. These materials were selected by the excellent magnetic properties, and the additives were chosen to make a stable suspension and give certain thixotropy for the particularity of being able to be sprayed into metal sheets.

Different experimental characterization techniques were applied to the samples. Firstly, XRD analysis for phase identification purposes and to measure the crystallite size of the powder agglomerates. Later, PSD analysis was made to ensure that nano-micro particles were obtained due to the impact of this to the rheological properties of final composite material. Moreover, different volume filling factors (VFF) of reinforced phase were studied.

For electromagnetic properties characterization, the magnetic characterization was performed using a SQUID magnetometer. The measurements consisted of obtaining key parameters such as saturation magnetization, remanent magnetization and hysteresis cycle of each material. In addition, waveguided analysis directly measures the physical constants such as electrical permittivity and magnetic permeability, important because they modify the Reflection Loss (RL) parameter used to determine the efficiency in microwave absorption.

Speakers: Mr Guillem Farré Vicente (Universitat de Barcelona), Dr Jaume Calvo-de la Rosa (DIOPMA Research Group, Departament de Ciència de Materials i Química Física, Departament de Física de la Matèria Condensada, Institut de Nanociència i Nanotecnologia (IN2UB), Universitat de Barcelona), Dr Pol Barcelona Pons (DIOPMA Research Group, Departament de Ciència de Materials i Química Física, Universitat de Barcelona)

Friday, 15 May

09:00 → 11:00 Invited Talks (IV)

09:00 From Molecular Response to Programmable Motion: Bio-Inspired 4D Micro-Structures

Recent advances in polymer chemistry and micro-fabrication have enabled the creation of adaptive materials capable of responding to external stimuli across multiple length scales. By integrating stimuli-responsive units at the molecular level with precise three-dimensional design, it is now possible to engineer synthetic systems that exhibit controlled motion, shape change and sensing. 1-3 This work showcases the development and structuring of responsive soft materials, including hydrogels and liquid crystal elastomers, using direct laser writing (DLW) via two-photon polymerisation (2PP). The combination of programmable micro-fabrication and intrinsic material responsiveness enables the realisation of sophisticated 4D microstructures that actuate on demand in response to light, temperature, electrochemical inputs, or changes in the local chemical environment. Fine, spatially resolved control over mechanical properties is achieved through modulation of laser writing parameters, allowing directional, anisotropic, and pre-programmed shape transformations to be encoded directly into three-dimensional architectures. Such adaptive microstructures demonstrate functions including controlled movement, and micro-scale actuation, highlighting the potential of these systems as bio-inspired platforms for applications ranging from soft micro-robotics and sensing to fluidics and drug delivery.

References:

1. Donato, S.; Nocentini, S.; Martella, D., Kolagatla, S.; Wiersma, D. S.; Parmeggiani, C.; Delaney, C.; Florea, L. Small 2023, 2306802.

2. Murphy, R. D.; Delaney, C.; Kolagatla, S.; Florea, L.; Hawker, C. J.,; Heise, A. Adv. Funct. Mat. 2023, 2306710.

3. Ennis, A.; Nicdao, D.; Kolagatla, S.; Dowling, L.; Tskhe, Y.; Thompson, A.J.; Trimble, D.; Delaney, C.; Florea, L., Adv. Funct. Mat. 2023, p.2213947.

4. del Pozo, M.; Delaney, C.; Pilz da Cunha, M.; Debije, M. G.; Florea, L., Schenning, A. P. Small Structures 2022, 3(2), 2100158.

Speaker: Larisa Florea (Trinity College Dublin)

09:30 Hydrogels for T-cell cancer therapy: a case of active wetting?

Hydrogels are ideal materials for mimicking the properties of natural tissues such as lymph nodes. Hydrogel interactions with cells and biomolecules can be well understood using appropriate simulation techniques, allowing a rational design of these materials for specific biomedical applications involving ex-vivo procedures. For example, we have recently proposed hydrogels for cancer immunotherapy specifically designed for enhanced CAR T-cell expression and expansion [1,2]. In optimizing the hydrogels, we found that their performance in cell culture has a nontrivial dependence on the mechanical properties of the hydrogels which has no obvious explanation. In this talk, I’ll argue that this crucial dependence of cell culture on the hydrogel mechanical properties is related to active wetting phenomena of cells on complex substrates.

[1] M. Castellote-Borrell, M. Domingo, F. Merlina, H. Lu, S. Colell, M. Bachiller, M. Juan, S. Guedan, J. Faraudo and J. Guasch “Lymph-Node Inspired Hydrogels Enhance CAR Expression and Proliferation of CAR T Cells”, ACS Appl. Mater. Interfaces 2025, 17, 11, 16548–16560.

[2] J. Guasch, M. Castellote, F. Merlina, J. Faraudo, M. Domingo, “Inverse opal hydrogel and its use in immunotherapy”, European Patent EP24382629, priority date 11 June 2024. International Publication number WO/2025/257179.A1.

Speaker: Jordi Faraudo (ICMAB-CSIC)

10:00 Non-equilibrium control of dissipative DNA-based systems and porous supramolecular materials

Recently, there has been growing interest in developing biomimetic strategies that provide enhanced spatiotemporal control over molecular self-assembly, enabling access to structures and properties that are unattainable under thermodynamic control. One approach involves mimicking the dissipative self-assembly of cytoskeletal microtubules, which continuously consume chemical fuels to regulate their supramolecular structure and function over time, operating in so-called non-equilibrium steady states (NESS). Over the past decade, a variety of chemically fueled artificial systems have been reported, in which energy-consuming reaction cycles are coupled to self-assembly processes. In parallel, DNA-based systems regulated by energy-dissipating mechanisms have also emerged. However, the vast majority of these systems rely on batchwise addition of chemical fuels in closed reactors, generating transient non-equilibrium states that contrast sharply with the sustained NESS observed in biological systems. In this talk, I will present an unprecedented example of a dissipative DNA-based system maintained at a non-equilibrium steady state, achieved through the continuous supply of an RNA fuel to a stirred semi-batch reactor, where it is enzymatically converted into waste. I will show how the system dynamically adapts to subtle variations in fuel supply, reaching different steady-state levels of a strand-displacement reaction in real time, thereby mimicking the behaviour of biological NESS. Furthermore, I will demonstrate how dissipative self-assembly can be harnessed to control the formation of porous supramolecular materials. In this case, the controlled supply of chemical fuels to a solution of building blocks (for example under diffusion-controlled conditions).

Speaker: Alessandro Sorrenti (Universitat de Barcelona)

10:30 Theory of self-chemophoresis

A frequent experimental realization of a microswimmer relies on self-chemophoresis. Chemophoresis (also called diffusiophoresis) denotes the motion of a particle immersed in a fluid solution due to a composition gradient. And self-chemophoresis pertains to the case that the gradient is generated by the particle itself through catalytic activity on its surface.

Conceptually one can write "phoretic velocity = phoretic coefficient x chemical gradient". In the "classic picture" of chemophoresis, the phoretic coefficient follows from linear response theory and the paradigm that "self-phoresis is normal phoresis but in a self-generated gradient" is usually invoked. We have shown, however, that this may not be the case because the activity of the particle can also affects the phoretic coefficient significantly, thus providing an alternative mechanism for self-propulsion.

We also predict that, in the apparently unrelated system of an intruder inmersed in a shaken granular bath, the intruder will self-propel according to this new mechanism. This unexpected connection will be discussed, with a focus on the complementarity between the two scenarios.

Speaker: Alvaro Domínguez

11:00 → 11:15 Pitch Presentations (III)

11:00 Trapping and Compressing Colloidal Quasi-Particles

The study of the formation of condensed, self-ordered phases has remained a central focus in the fields of condensed matter physics and particle physics over the past few decades. Examples of systems capable of forming ordered phases under confinement include electrons on the surface of liquid helium, electrons in quantum dots, and charged particles suspended in plasma1,2. A common characteristic among these systems is that they consist of particles with long-range repulsive interactions, typically confined by either parabolic or hard-wall potentials. Under such conditions, a typical structural arrangement is the Wigner crystal, which in two dimensions corresponds to a perfectly ordered triangular lattice. Systems forming 2D Wigner crystals under circular confinement—whether parabolic or hard-wall—have been identified as simplified models of 2D Thomson atoms3, exhibiting characteristic shell-like arrangements. However, such systems often rely on complex experimental architectures and demand sophisticated analysis techniques. Here, we propose a novel mesoscopic model based on solitary waves that can replicate the properties of condensed, self-ordered phases. Specifically, in a strongly confined nematic chiral liquid crystal. metastable toron-like structures can be generated in the form of solitary waves. These behave similarly to solid colloidal particles, with the unique feature that they are not physical entities with mass, but rather localised perturbations in the orientational order of the liquid crystal medium. The combination of elastic interactions arising from these local perturbations, the ability to control packing density, and the capacity to generate laterally confining structures within the liquid crystal leads to the emergence of highly ordered configurations reminiscent of 2D Wigner-like assemblies. Furthermore, when subjected to strong external perturbations—such as the application of lateral pressure—these torons can be annihilated, resulting in a malleable confined system. In this work, we investigate the behaviour of torons confined within a circular trap generated using holographic optical tweezers. We explore the dynamics of these solitonic structures under radial compression and demonstrate the existence of specific “magic numbers” corresponding to particularly stable configurations that exhibit shell-like ordering. We also show the stabilising capacity that the application of an electric field can have towards compression. Furthermore, we uncover the mechanism underlying the annihilation process that occurs under compression, highlighting its strong correlation with the coordination number of the solitons.

Speaker: Joel Torres Andrés (Universitat de Barcelona)

11:05 Universal transport of active colloids with sensory delay in motility landscapes

We experimentally, numerically and analytically explore the diffusive transport of active colloidal particles with sensory delay, navigating motility landscapes in which the self--propulsion speed depends on space. We show how the transport properties can be obtained by replacing the space dependence of the self--propulsion speed by a dynamical stochastic switching process in the absence of delay, and extend the theory for systems with finite delayed responses. We obtain analytical results for the mean square displacement and the effective diffusion coefficient which accurately predict experimental measurements and numerical simulations across multiple scales. We show how, within the regime of validity of the delay-extended theory, density patterns and effective diffusion obey universal scaling forms. Our work provides minimal framework describing the transport properties of active swimmers with internal adaptation dynamics in motility landscapes.

Speaker: Adrià Garcés Ortiz (Universitat de Barcelona)

Universal transport of active colloids with sensory delay in motility landscapes

11:10 From Nucleation to Architecture: Shaping Single Crystals at the Millimeter Scale

Morphological control of crystals is utterly important in reticular chemistry, especially as a fundamental strategy toward preparing functional materials of superior properties. Despite the notable advancements in the realm of metal-organic frameworks (MOFs), where endeavors primarily focus on shape manipulation at the nano- and microscale during bulk synthesis and subsequent processing at the mesoscale (e.g., incorporation into polycrystalline films, patterns, and composites), a notable challenge persists in attaining a meticulous control over both the shape and size of macroscopic single crystals.
Here we successfully demonstrated the spatial and morphological control of crystal growth at the millimeter scale from a non-equilibrium state through the utilization of a microfluidic device. Specifically, we employed PDMS channels to confine CuGHG, a peptide-based MOF, where crystal formation occurred as a consequence of a diffusion-controlled supply of precursors within an advection-free microenvironment. Depending on the concentration of the feeding solution, continuous growth or shrinkage of the crystals was observed and recorded by time-lapse microscope. Our method not only introduces a novel approach for precisely shaping large-scale single crystals from metastable solutions but also draws attention to its intriguing resemblance to two fundamental morphogenesis strategies observed in biomineralization. The presented results, therefore, establish a fundamental basis for future studies in materials science, shedding light on how the size and shape of artificial crystals can intricately influence their properties and functions.Moreover, our findings provide a strategic avenue for tailoring the size and shape of peptide-based MOF single crystals to specific applications. This approach not only expands the horizons of crystal engineering but also opens up possibilities for the design and customization of materials with desired properties for various technological applications.

Speaker: Thao Nguyen (Universitat de Barcelona)

11:15 → 11:45 Coffee Break / Poster Session (III)

11:15 Computational Modelling of Protein Corona Formation on Lipid Nanoparticles: Hard Corona and Polydispersity Effects

Computational Modelling of Protein Corona Formation on Lipid Nanoparticles: Hard Corona and Polydispersity Effects
Fiona Gallach1,2*, Oriol Vilanova1,2, Alberto Martinez-Serra3, Marco Monopoli4, Giancarlo Franzese1,2
1Departament de Física de la Matèria Condensada, Facutat de Física, Universitat de Barcelona, Marti i Franques 1, 08028 Barcelona, Spain
2Institute of Nanoscience and Nanotechnology (IN2UB), Universitat de Barcelona, Marti i Franques 1, 08028 Barcelona, Spain
2 Barcelona Supercomputing Center (BSC), Barcelona, Spain
3 Royal College of Surgeons in Ireland (RCSI), Dublin, Ireland
fgallach7@alumnes.ub.edu

Introduction
When lipid nanoparticles (LNPs) enter biological fluids, proteins adsorb onto their surface, forming a biomolecular corona that consists of a tightly bound hard corona (HC) and a loosely associated soft corona (SC). This corona influences their pharmacokinetics and cellular fate. Computational modeling of HC formation is essential for the rational design of LNP-based drug delivery systems 1.

Materials & Methods
A coarse-grained (CG) model was employed to describe human serum albumin (HSA)–LNP interactions using a potential that combines van der Waals attraction, electrostatic repulsion, and Born repulsion. The interaction strength was calibrated by fitting simulated adsorption isotherms to experimental surface coverage data (0–10 mg/mL HSA) for an LNP with radius R = 90 nm, yielding an optimal interaction strength of 7.25 kBT. Additional simulations at R = 87 nm and R = 93 nm were performed to mimic the experimental polydispersity [2].

Results and Discussion
The calibrated model closely matches the experimental HSA adsorption isotherm, accurately capturing both initial adsorption and surface saturation. Simulations at R = 87 nm and R = 93 nm align well with the baseline case, suggesting that a polydispersity of ±3 nm has minimal impact on HC formation. Consistently, the potential wells for R = 50 nm, 90 nm, and 93 nm are nearly identical in depth and position, indicating that the binding energy landscape remains largely unaffected by small changes in curvature within this size range. Ongoing analysis, including cooperative effects from three-body protein–protein–NP interactions, aims to further refine the model's alignment with experimental results. These preliminary findings confirm the effectiveness of the CG framework for modeling HSA corona formation and pave the way for future research on Vroman-type competitive exchange under physiological conditions.

References
1 F. Spinozzi, P. Moretti, D. R. Perinelli, G. Corucci, P. Piergiovanni, H. Amenitsch, G. A. Sancini, G. Franzese, and P. Blasi. Small-angle x-ray scattering unveils the internal structure of lipid nanoparticles. Journal of Colloid and Interface Science, 662, 446 (2024).
[2] O. Vilanova, A. Martinez-Serra, M. P. Monopoli, and G. Franzese. Characterizing the hard and soft nanoparticle-protein corona with multilayer adsorption. Frontiers in Nanotechnology, 6, 1531039, (2025).

Speaker: Fiona Gallach (UB)

11:15 From Nucleation to Architecture: Shaping Single Crystals at the Millimeter Scale

Morphological control of crystals is utterly important in reticular chemistry, especially as a fundamental strategy toward preparing functional materials of superior properties. Despite the notable advancements in the realm of metal-organic frameworks (MOFs), where endeavors primarily focus on shape manipulation at the nano- and microscale during bulk synthesis and subsequent processing at the mesoscale (e.g., incorporation into polycrystalline films, patterns, and composites), a notable challenge persists in attaining a meticulous control over both the shape and size of macroscopic single crystals.
Here we successfully demonstrated the spatial and morphological control of crystal growth at the millimeter scale from a non-equilibrium state through the utilization of a microfluidic device. Specifically, we employed PDMS channels to confine CuGHG, a peptide-based MOF, where crystal formation occurred as a consequence of a diffusion-controlled supply of precursors within an advection-free microenvironment. Depending on the concentration of the feeding solution, continuous growth or shrinkage of the crystals was observed and recorded by time-lapse microscope. Our method not only introduces a novel approach for precisely shaping large-scale single crystals from metastable solutions but also draws attention to its intriguing resemblance to two fundamental morphogenesis strategies observed in biomineralization. The presented results, therefore, establish a fundamental basis for future studies in materials science, shedding light on how the size and shape of artificial crystals can intricately influence their properties and functions.Moreover, our findings provide a strategic avenue for tailoring the size and shape of peptide-based MOF single crystals to specific applications. This approach not only expands the horizons of crystal engineering but also opens up possibilities for the design and customization of materials with desired properties for various technological applications.

Speaker: Thao Nguyen (Universitat de Barcelona)

11:15 Hydrodynamic Viscous Levitation of Magnetically Driven S-Shape Propellers

Microorganisms and microscale entities swimming in fluids at low Reynolds number (Re) need to devise innovative ways of propulsion to avoid reciprocal motion [1]. A way to break the time-reversible nature of fluid flow at low Re is to use the proximity of a boundary surface. In this work, we design an innovative S-shape micro propeller that rises and levitates from a close plane due to hydrodynamic interactions with the surface. Using soft-lithography and external magnetic driving, we demonstrate the field-tunable levitation of these S-shape filaments. These propellers are made of superparamagnetic silica-coated nanoparticles in a reticulated polymer matrix assembled following a previously established microfabrication technique [2]. The filaments are dispersed in water mixed with glycerol to adjust the medium viscosity. The propellers rotate synchronously with the external field, rising and hovering at a fixed distance from the surface. We then analyze how the equilibrium height of levitation depends only on the rotating frequency of the object for a fixed viscosity of the fluid, and for a fixed size and shape of the propeller. Thus, we introduce a generic, shape-induced hydrodynamic levitation technique which can be extended to other driven or active self-propelling particles for potential applications in micro-robotics and drug-delivery in microfluidic systems.

References:
[1] E. M. Purcell; Life at low Reynolds number. Am. J. Phys. 45, 3–11 (1977).
[2] J. W. Tavacoli, et al., The fabrication and directed self-assembly of micron-sized superparamagnetic non-spherical particles. Soft Matter 9.38 (2013).

Speaker: Guillermo Cassinello Toscano (Universitat de Barcelona)

11:15 Impact of metal binding in the structure of peptide hydrogels

Hydrogels are hydrophilic polymeric networks characterized by high water content, permeability, and tunable properties, which make them attractive materials for biomedical applications such as drug delivery, tissue engineering, wound healing, biosensors, bioinks, and catalysis.

Within this framework, peptide‑based hydrogels are particularly appealing due to their mild fabrication conditions, biocompatibility, biodegradability, and functional versatility. However, their limited mechanical strength and slow gelation kinetics remain major challenges that restrict their biomedical applicability.

Herein, we present preliminary results on how both the mechanical performance and biomedical potential of peptide‑based hydrogels can be significantly modified through crosslinking with metal ions.

Speakers: Ana B. Caballero (Universitat de Barcelona), Nevil Jose (University of Barcelona)

11:15 SWIMMING PRESSURE-DRIVEN TRANSPORT AND PATTERNING OF LIGHT-ACTIVATED COLLOIDS

Light-activated Janus microswimmers offer a programmable active-matter platform in which illumination modulates propulsion and enables controlled density modulations and localization [1,2]. We develop a continuum theory model that captures swimming pressure and the resulting dynamic pattern formation in spatially structured activity landscapes. Our framework couples a conservation law for the colloid concentration to a light-dependent swim speed, with swimming pressure acting as an effective nonequilibrium stress that biases fluxes and shapes interfaces.

From this model we extract three emergent timescales: (i) depletion in the bright (active) zone, (ii) filling in the dark (inactive) zone, and (iii) interfacial formation/relaxation in a shady transition zone. We further derive a Lyapunov functional for the coarse-grained dynamics, enabling direct determination of the quiescent-state concentration profile. Finally, when imposing a traveling-wave bright field (a moving activity pattern), we predict a net particle flux opposite to wave propagation direction and whose magnitude depends on the wave speed, yielding a tunable mechanism for rectified transport (“optical pumping”) under structured illumination protocols [3].

References

[1] Töpfer, U.; Bailey, M. R.; Schreiber, S.; Paratore, F.; Isa, L. Density Modulations in Active Colloidal Systems through Orthogonal Propulsion Control and Sensory Delays. ACS Nano 19, 39210–39219 (2025). DOI: https://doi.org/10.1021/acsnano.5c12596

[2] Palacci, J.; Sacanna, S.; Kim, S.-H.; Yi, G.-R.; Pine, D. J.; Chaikin, P. M. Light-activated self-propelled colloids. Philos. Trans. R. Soc. A 372 (2029), 20130372 (2014). DOI: https://doi.org/10.1098/rsta.2013.0372

[3] Chen, X.; Xu, Y.; Lou, K.; Peng, Y.; Zhou, C.; Zhang, H. P.; Wang, W. Programmable, Spatiotemporal Control of Colloidal Motion Waves via Structured Light. ACS Nano 16, 12755–12766 (2022). DOI: https://doi.org/10.1021/acsnano.2c04596

Speaker: Miguel Ángel Chamorro Burgos (Universidad de Sevilla)

11:15 Trapping and Compressing Colloidal Quasi-Particles

The study of the formation of condensed, self-ordered phases has remained a central focus in the fields of condensed matter physics and particle physics over the past few decades. Examples of systems capable of forming ordered phases under confinement include electrons on the surface of liquid helium, electrons in quantum dots, and charged particles suspended in plasma1,2. A common characteristic among these systems is that they consist of particles with long-range repulsive interactions, typically confined by either parabolic or hard-wall potentials. Under such conditions, a typical structural arrangement is the Wigner crystal, which in two dimensions corresponds to a perfectly ordered triangular lattice. Systems forming 2D Wigner crystals under circular confinement—whether parabolic or hard-wall—have been identified as simplified models of 2D Thomson atoms3, exhibiting characteristic shell-like arrangements. However, such systems often rely on complex experimental architectures and demand sophisticated analysis techniques. Here, we propose a novel mesoscopic model based on solitary waves that can replicate the properties of condensed, self-ordered phases. Specifically, in a strongly confined nematic chiral liquid crystal. metastable toron-like structures can be generated in the form of solitary waves. These behave similarly to solid colloidal particles, with the unique feature that they are not physical entities with mass, but rather localised perturbations in the orientational order of the liquid crystal medium. The combination of elastic interactions arising from these local perturbations, the ability to control packing density, and the capacity to generate laterally confining structures within the liquid crystal leads to the emergence of highly ordered configurations reminiscent of 2D Wigner-like assemblies. Furthermore, when subjected to strong external perturbations—such as the application of lateral pressure—these torons can be annihilated, resulting in a malleable confined system. In this work, we investigate the behaviour of torons confined within a circular trap generated using holographic optical tweezers. We explore the dynamics of these solitonic structures under radial compression and demonstrate the existence of specific “magic numbers” corresponding to particularly stable configurations that exhibit shell-like ordering. We also show the stabilising capacity that the application of an electric field can have towards compression. Furthermore, we uncover the mechanism underlying the annihilation process that occurs under compression, highlighting its strong correlation with the coordination number of the solitons.

Speaker: Joel Torres Andrés (Universitat de Barcelona)

11:15 Universal transport of active colloids with sensory delay in motility landscapes

We experimentally, numerically and analytically explore the diffusive transport of active colloidal particles with sensory delay, navigating motility landscapes in which the self--propulsion speed depends on space. We show how the transport properties can be obtained by replacing the space dependence of the self--propulsion speed by a dynamical stochastic switching process in the absence of delay, and extend the theory for systems with finite delayed responses. We obtain analytical results for the mean square displacement and the effective diffusion coefficient which accurately predict experimental measurements and numerical simulations across multiple scales. We show how, within the regime of validity of the delay-extended theory, density patterns and effective diffusion obey universal scaling forms. Our work provides minimal framework describing the transport properties of active swimmers with internal adaptation dynamics in motility landscapes.

Speaker: Adrià Garcés Ortiz (Universitat de Barcelona)

11:15 Viscosity and Diffusion in ionic auqueous solutions.

Many soft and biological systems operate in ionic environments where salts significantly influence water transport and stability. In aqueous electrolyte solutions, viscosity and diffusivity are often described by the empirical Jones–Dole relation and commonly discussed in terms of structure-making (kosmotropic) or structure-breaking (chaotropic) ions [1]. However, the physical basis and the robustness of these trends remain subjects of debate. Therefore, we aim to develop a computationally efficient framework to capture these transport behaviors and extend the analysis to less-explored regimes with limited experimental data.We modify a cooperative coarse-grained water model, previously demonstrated to qualitatively reproduce key water anomalies [2], to include ionic effects in a mean-field manner without explicit ions. Ionic influences are incorporated through concentration-dependent changes in: (i) the directional hydrogen-bond interactions between water molecules and (ii) the effective volume associated with hydrogen-bond fluctuations, guided by experimental data [3]. Simulations are conducted within a Monte Carlo NPT ensemble, enabling efficient sampling and extraction of transport properties such as viscosity and diffusivity.The proposed framework qualitatively captures Jones–Dole-like trends in viscosity and diffusivity over a wide concentration range, including deviations at higher concentrations that are consistent with experimental findings. Extending the study to varying pressures reveals an asymmetric response: structure-making behavior remains stable across the conditions examined, while structure-breaking behavior becomes pressure-dependent, exhibiting a crossover at elevated pressures. In conclusion, the model successfully reproduces the key trends related to structure-making and structure-breaking ions, providing predictive insights even in regimes with sparse experimental data.

[1] Jones, G.; Dole, M. J. Am. Chem. Soc. 51 (1929) 2950–2964. DOI: 10.1021/ja01385a012.
[2] de los Santos, F.; Franzese, G. J. Phys. Chem. B 115 (2011) 14311–14320. DOI:
10.1021/jp206197t.
[3] Corridoni, T.; et al. J. Phys. Chem. B 115 (2011) 14008–14013. DOI: 10.1021/jp202755u.

Speaker: Santiago Pelosso Rodriguez (Universidad de Barcelona)

11:45 → 12:45 Invited Talks (V)

11:45 Scaling, ripening and division in emulsions of chemically active droplets

In recent years, many efforts have been devoted to characterising liquid mixtures composed of molecules that interact and undergo chemical reactions, such as the cell cytoplasm or pools of short polymers that mimic the primordial soup. In such mixtures, condensates that form via phase separation play a key role. Here, I review the theory of phase separation in the presence of chemical reactions among the mixture's components, focusing on reactions kept away from equilibrium by continuous turnover of chemical fuel. I first characterise a new class of out-of-equilibrium stationary states composed of spherical shells that have recently been observed in experiments using active coacervates. Then I describe emulsions composed of many chemically active droplets. In particular, I discuss which factors determine the size and scaling of active droplets, and which are the physical determinants of droplet ripening and droplet division.

Speaker: Giacomo Bartolucci (Universitat de Barcelona)

12:05 Emergent active motion of Brownian colloids in living and driven chiral media

Brownian colloids can acquire effective activity when immersed in a dense, out-of-equilibrium medium. In these environments, the surrounding particles continuously transfer energy to the colloids, generating persistent, non-equilibrium fluctuations that can drive ballistic motion at short times and enhanced diffusion at long times. In this talk I will present two distinct scenarios in which activity is introduced through a surrounding, externally controlled medium, allowing us to tune fluctuations and probe their effects in different regimes.
First, I will show a two-dimensional colloidal crystal activated by a bath of light-driven bacteria. In this system, thermal and active fluctuations coexist and can be independently controlled via magnetic interactions and bacterial activity. By analyzing the crystal’s relaxation modes, we show that for short persistence times, the system is well described by a single effective temperature, while for more persistent activity the equipartition of energy among modes is broken and multiple mode-dependent temperatures emerge.
Finally, I will present a second system where activity is generated by a driven medium: a chiral fluid of rotating magnetic microparticles. Depending on the driving conditions, this system forms either phase-separated rotating clusters or a homogeneous chiral fluid. Passive particles in these environments acquire effective active motion from the hydrodynamic flows generated by the rotors, with long persistence times and strongly enhanced diffusion at long times.
Together, these results illustrate how distinct mechanisms of energy injection, from living bacterial baths to driven chiral flows, can be used to control active fluctuations and study their emergent phenomena in both solid and fluid colloidal systems.

Speaker: Helena Massana (Universitat de Barcelona)

12:25 Active Brownian Information Engine and Beyond

Many biological systems operating in athermal (active) environments, can be modelled as an information engine, with the key aspect of utilizing information on the fluctuation to extort work from the noisy environment[1]. In this study, we propose a feedback-driven information engine operating in a Gaussian-correlated active reservoir with characteristic strength (Da) and correlation time (ta), which outperforms its thermal counterpart [2,3]. We obtain the optimal functioning criteria for the enhanced performance of the active Brownian information engine (ABIE), reliant on the dispersion of the steady state, which is analogous to its passive analogue [3]. We notice that a weakly correlated active bath extracts colossal work due to the reduced relative loss of information in the relaxation process. In the limit of fractionally smaller correlation time (a /r 0, is thermal relaxation time), the upper bound on colossal work extraction is 0.202(D+Da). The excess amount of extracted work reduces and converges to its passive counterpart in the higher limit of correlation time (a /r ). Interestingly, when correlation time is equivalent to relaxation time, half the upper bound of excess work is achieved irrespective of activity strength. This study provides a new insight into understanding and designing the information-energy exchange of biological submicrometer motors.

If time permits I would also like to discuss our ongoing experimental exploration of the nonequilibrium thermodynamics at the single-cell level. Using the optical tweezers microscopy, fluctuating nanoscale systems can be monitored to probe their dynamics. This framework also enables the experimental verification of mean first passage time studies, as well as realisation of small-scale heat engines[4].

References

1. J., Parrondo, J., Horowitz, T., Sagawa, Nat. Phys., 2015, 11, 131.

2. R., Rafeek, S., Y., Ali, D., Mondal, Phys. Rev. E, 2023, 107, 044122.

3. R., Rafeek, D., Mondal, J. Chem. Phys., 2024, 161, 124116.

4. T., Tohme, V., Bedoya, C., D., Bello, L., Bresque, G., Manzano, É., Roldán, Phys. Rev. Lett., 2025, 135, 067101.

Speaker: Rafna Rafeek (Abdus Salam International Center for Theoretical Physics Trieste)

12:45 → 13:30 Roundtable

13:30 → 13:45 Closing