Selectively manipulable acoustic-powered microswimmers

Selective actuation of a single microswimmer from within a diverse group would be afirst step toward collaborative guided action by a group of swimmers. Here wedescribe a new class of microswimmer that accomplishes this goal. Our swimmer designovercomes the commonly-held design paradigm that microswimmers must use non-reciprocal motion to achieve propulsion; instead, the swimmer ispropelled by oscillatory motion of an air bubble trapped within theswimmer's polymer body. This oscillatory motion is driven by theapplication of a low-power acoustic field, which is biocompatible with biologicalsamples and with the ambient liquid. This acoustically-powered microswimmeraccomplishes controllable and rapid translational and rotational motion, even inhighly viscous liquids (with viscosity 6,000 times higher than that of water). Andby using a group of swimmers each with a unique bubble size (and resulting uniqueresonance frequencies), selective actuation of a single swimmer from among the groupcan be readily achieved.