Anomalous dynamics of an elastic membrane in an active fluid

Using numerical simulations, we characterized the behavior of an elastic membrane immersed in an active fluid. Our findings reveal a nontrivial folding and re-expansion of the membrane that is controlled by the interplay of its resistance to bending and the self-propulsion strength of the active components in solution. We show how flexible membranes tend to collapse into multi-folded states, whereas stiff membranes oscillates between an extended configuration and a singly folded state. This study provides a simple example of how to exploit the random motion of active particles to perform mechanical work at the micro-scale.

Curvature Induced Activation of a Passive Tracer in an Active Bath

We use numerical simulations to study the motion of a large asymmetric tracer immersed in a low density suspension of self-propelled nanoparticles in two dimensions. Specifically, we analyze how the curvature of the tracer affects its translational and rotational motion in an active environment. We find that even very small amounts of curvature are sufficient for the active bath to impart directed motion to the tracer which results in its effective activation. We propose simple scaling arguments to characterize this induced activity in terms of the curvature of the tracer and the strength of the self-propelling force. Our results suggest new ways of controlling the transport properties of passive tracers in an active medium by carefully tailoring their geometry.

Anomalous Thermomechanical Properties of a Self-propelled Colloidal Fluid

We use numerical simulations to compute the equation of state of a suspension of spherical, self-propelled nanoparticles. We study in detail the effect of excluded volume interactions and confinement as a function of the system temperature, concentration and strength of the propulsion. We find a striking non-monotonic dependence of the pressure with the temperature, and provide simple scaling arguments to predict and explain the occurrence of such an anomalous behavior. We conclude the paper by explicitly showing how our results have an important implications for the effective forces exerted by fluids of self-propelled particles on passive, larger components.