Effect of body shape on the motile behavior of bacteria-powered swimming microrobots (BacteriaBots)

Swimming microrobots are envisioned to impact minimally invasive diagnosis, localized treatment of diseases, and environmental monitoring. Dynamics of micro-scale swimming robots falls in the realm of low Reynolds number, where viscous forces exerted on the robots are dominant over inertia. Viscous forces developed at the interface of the swimming microrobots and the surrounding fluid are a strong function of the body geometry. In this work, a collection of bacteria-powered micro-robots (BacteriaBots) with prolate spheroid, barrel, and bullet-shaped bodies is fabricated and the influence of body shape on the dynamics of the BacteriaBots is investigated. We have experimentally demonstrated that using non-spherical geometries increases the mean directionality of the motion of the BacteriaBots but does not significantly affect their average speed compared with their spherical counterparts. We have also demonstrated that directionality of non-spherical BacteriaBots depends on the aspect ratio of the body and for the case of prolate spheroid, a higher aspect ratio of two led to a larger directionality compared to their low aspect ratio counterparts.