3D printed large amplitude torsional microactuators powered by ultrasound

Here, we introduce a design, fabrication, and control methodology for large amplitude torsional microactuators powered by ultrasound. The microactuators are 3D printed from two polymers with drastically different elastic moduli as a monolithic compliant mechanism, and contain precisely engineered capsules with multiple orifices that serve as stators and rotors. Secondary acoustic radiation forces generated among the encapsulated air bubbles controllably rotate the rotor that is supported and stabilized by two torsion bars. The capsules are designed according to the simulations of an analytical model that captures the dynamics of the water-air interface vibrations, which we rigorously validate using a laser Doppler vibrometer and phase-contrast imaging. An in-depth experimental sensitivity analysis is conducted to optimize the arrangement of the rotor and the stators. Integration of experimental results with finite element analysis of the twisting bars and analytical modelling of acoustic phenomena allows us to compute the secondary acoustic radiation forces and the angular displacement of the rotor for a given input pressure. The versatility of the design framework and the robust performance of the printed actuators enable the development of a new class of microscale machines and soft robotic devices that are actuated and controlled by sound waves.