  The concept of creating all-mechanical soft microrobotic systems has great
potential to address outstanding challenges in biomedical applications, and
introduce more sustainable and multifunctional products. To this end, magnetic
fields and light have been extensively studied as potential energy sources. On
the other hand, coupling the response of materials to pressure waves has been
overlooked despite the abundant use of acoustics in nature and engineering
solutions. Here, we show that programmed commands can be contained on 3D
nanoprinted polymer systems with the introduction of selectively excited air
bubbles and rationally designed compliant mechanisms. A repertoire of
micromechanical systems is engineered using experimentally validated
computational models that consider the effects of primary and secondary
pressure fields on entrapped air bubbles and the surrounding fluid. Coupling
the dynamics of bubble oscillators reveals rich acoustofluidic interactions
that can be programmed in space and time. We prescribe kinematics by harnessing
the forces generated through these interactions to deform structural elements,
which can be remotely reconfigured on-demand with the incorporation of
mechanical switches. These basic micromechanical systems will serve as the
building blocks for the development of a novel class of untethered soft
microrobots powered and controlled by acoustic signals.
