Ultrasound-Driven Programmable Artificial Muscles

Muscular systems1, the fundamental components of mobility in animals, have sparked innovations across technological and medical fields2,3. Yet artificial muscles suffer from dynamic programmability, scalability, and responsiveness due to complex actuation mechanisms and demanding material requirements. Here, we introduce a design paradigm for artificial muscles, utilizing >10,000 microbubbles with targeted ultrasound activation. These microbubbles are engineered with precise dimensions that correspond to distinct resonance frequencies. When stimulated by a sweeping-frequency ultrasound, microbubble arrays in the artificial muscle undergo selective oscillations and generate distributed point thrusts, enabling the muscle to achieve programmable deformation with remarkable attributes: a high compactness of [~]3,000 microbubbles/mm{superscript 2}, a low weight of 0.047 mg/mm2, a substantial force intensity of [~]1.21 N/mm2, and fast response (sub-100 ms during gripping). Moreover, they offer good scalability (from micro- to -centimeter scale), exceptional compliance, and many degrees of freedom. We support our approach with a theoretical model and demonstrate applications spanning flexible organism manipulation, conformable robotic skins for adding mobility to static objects and conformally attach to ex vivo porcine organs, and biomimetic stingraybots for propulsion within ex vivo biological environments. The customizable artificial muscles could offer both immediate and long-term impact on soft robotics, wearable technologies, haptics, and biomedical instrumentation.