Chiral active metamaterials

Active liquids are composed of self-driven microbots that endow the liquid with a unique set of mechanical characteristics. We design metamaterials using polar active liquids, i.e., liquids that flow spontaneously and without the need of external forcing. Specifically, we create chiral steady-state flow using periodically shaped microchannels. This induced flow gives rise to topologically protected density waves, which are robust against both disorder and backscattering. Furthermore, active liquids composed of self-spinning rotors are chiral by design, a feature reflected in their constitutive relations.

In two dimensions, the viscosity of such liquids includes an extra component called odd (or Hall) viscosity. Odd viscosity provides no energy dissipation, but couples pressure to vorticity. We explore how this coupling may be exploited to design self-assembled hydraulic cranks that convert between linear and rotational motion in microscopic machines powered by active rotors.