Speaker
Description
Controlling the transport of micro and nano particles in liquids is a fundamental problem with the potential to revolutionize different emerging technologies [1]. The use of self-generated thermal gradients has been theoretically proposed and demonstrated in experiment to be a promising strategy to induce transport of microparticles in liquids [2]. Here we show that the anisotropic dissipation of excess molecular energy into the surrounding solvent can lead to the propulsion of nanoparticles [3]. We use all-atomic models of excited nanoparticles and of the solvent to investigate with molecular dynamics simulations the emergent particle propulsion as the excess energy is dissipated into the solvent. We report results in liquid water from: (i) nanoparticles functionalized with excited fluorophores [3]; (ii) high energy vibrationally excited molecules [4]. In both cases we find a marked energy flux anisotropy during relaxation which results in a temperature gradient across the nanoparticle and in a net propulsion that leads to significant enhanced diffusion when periodic excitations are applied. In contrast to most models of self-phoresis, we find that propulsion occurs via short (≲ 0.5ps) impulses. From our all-atomic description we identify the source of propulsion as a transient force imbalance with the surrounding solvent when hydrogen bonds are broken as a result of the prescribed molecular excitations. Finally, strategies to direct the motion of functionalized nanoparticles in a given direction using confined environments are also discussed.
References
[1] C. Bechinger, R. Di Leonardo, H. Löwen, C. Reichhardt, G. Volpe and G. Volpe, Rev. Mod. Phys. 88 (2016) 045006.
[2] H-R. Jiang, N. Yoshinaga and M. Sano, Phys. Rev. Lett. 105 (2010) 268302.
[3] C. Calero, E. L. Sibert III, R. Rey, Nanoscale 12 (2020) 7557.
[4] A. Jurado Romero, C. Calero, E. L. Sibert III, R. Rey, J. Chem. Phys. 158 (2023) 194501.
