Self propelling nematic microcapsules*

The ability to produce controllable, self propelling microcapsules is of great interest to synthetic biology and the design of smart microreactors. Inactive fluid shells are already widely used as artificial cell models, micro-reactors, and in food and drug applications. However, combining activity, stability, and control remains a significant challenge. Building on an established active emulsion platform, we have developed a new approach to the problem of encapsulation by using nematic active double emulsions, where a solubilization mechanism induces activity and the molecular nematicity provides stability. We show that using a nematic liquid crystal as the shell material with homeotropic anchoring at both interfaces will result in a nematoelastic force on a displaced core droplet and act as a topological barrier against the coalescence of the core droplet with the outer phase. We further present a peculiar self-propulsion mode where the interplay of spontaneous symmetry breaking and autochemotaxis results in a "shark-fin meandering" motion of the shell in a 2D-confined geometry and helical swimming in 3D. This behavior can be controlled or switched off by introducing chemical gradients, topographical guidance or by changing the shell topology.