Extrusion of active rods through 3D microchannels with various cross-sectional shapes

The active rod model describes many biological and biomimetic micro-swimmers that have an elongated shape and the ability to transduce energy into persistent autonomous motion while swimming. This model successfully captures phenomena associated with confined active matter, such as boundary accumulation and upstream swimming. These phenomena significantly influence the cross-sectional distributions of active rods as they are transported through microchannels. In this work, we elucidate how the cross-sectional distribution of active rods and their concentration profiles along the microchannel depend on the microchannel's cross-sectional shape. Our focus is on shapes with non-constant curvatures and corners. In particular, we show how boundary accumulation at locations of highest curvature is affected by the background flow along the microchannel. We also investigate the role of the wall torque exerted on accumulated active rods. For flat walls, this torque reorients an active rod to be tangent to the wall, allowing the rod to escape from wall entrapment. We demonstrate, both theoretically and numerically, that in the case of a curved wall, entrapment at locations of highest curvature can be stable, even when the wall torque is considered.

This is a joint work with Chase Brown (UC Riverside) and Shawn D. Ryan (Cleveland State University).