Speaker
Description
We assemble a biomimetic active material from microscopic components like cells' filaments and protein motors that consume energy and generate continuous motion. Such active systems are capable of self-organization at different length and time scales, often exhibiting turbulent flows and the emergence of long-range orientational order, which is a characteristic of active nematics (AN). Previously, it was demonstrated that, by bringing into contact a two-dimensional AN with an anisotropic oil that features smectic liquid-crystalline order, it is possible to transform the originally turbulent flow of the active fluid into well-aligned flows ordered by a magnetic field [1]. Alternatively, the flow of active nematic could be controlled by confining walls [2] or arrangements of obstacles [3].
n present work we combine both approaches: well-aligned flows of AN ordered by a magnetic field were confined between walls of PDMS channels. The resulting quasi-laminar flows of AN are perturbed by closely located channel walls and reorganized in arrays of vortexes forming an hexagonal lattice. The emergence of vortex lattices is correlated with positional ordering of topological defects and the appearance of density patterns. The observed self-organization of the active flows is activity dependent and reflects the inherent properties of the aligned AN. The described system is an example of pattern formation from instabilities of AN flows and suggests potential applications in the design and control of active materials.
[1] P. Guillamat, et al., Proc. Natl. Acad. Sci. U. S. A., 113, 20 (2016).
[2] J.Hardoüin et al., Soft Matter, 16, (2020).
[3] B. Zhang, et al., Phys. Rev. Research, 2, 4 (2020).
