Untethered miniature soft robots offer significant potential in biomedical and industrial applications due to their accessibility and safe interaction. This paper presents a focused ultrasound-controlled phase transition (FUPT) strategy for achieving millimeter-level spatially selective actuation and Newton-level force output in soft robots. The method uses ultrasound-induced heating to trigger a phase transition, enabling powerful actuation through inflation. The high spatial resolution allows a single robot to perform multiple tasks. Demonstrations include liquid cargo delivery and a biopsy robot for tissue acquisition and patching. An autonomous control system integrates ultrasound imaging for automatic acoustic field alignment and control, advancing the spatiotemporal response capability of untethered miniature soft robots.

Bo Hao, Xin Wang, Yue Dong, Mengmeng Sun, Chen Xin, Haojin Yang, Yanfei Cao, Jiaqi Zhu, Xurui Liu, Chong Zhang, Lin Su, Bing Li, Li Zhang