Optical spatio-temporal control of active matter systems in 2-D.

Active matter systems consist of self-driven units which convert chemical energy into mechanical energy and organize themselves into various patterns. Their pattern and flow properties exhibit non-equilibrium properties. In our experiments, we investigate the pattern formation of microtubule, kinesin motor kinesin motor proteins in 2-D fluid/fluid interfaces. The kinesin motor proteins are engineered in a way that light induces reversible linkage between them. Thus, under the exposure to the light (blue light centered at wavelength 460nm) the end groups of kinesin motor proteins bind and create the sliding motion between the microtubule bundles. Due to topological constraints, bundles create + ½ (motile) and - ½ (non-motile) defects. Using various light patterns, we confine the sample both in space and time. Illuminated regions exhibit strong bundling where the flow patterns and speed of the + ½ defects depend on the power and the design of the light pattern. Our goal is to control the defect velocity and their direction to guide them towards a certain destination.