Sensor‐Embedded Muscle for Closed‐Loop Controllable Actuation in Proprioceptive Biohybrid Robots

Abstract

Biohybrid robots are soft robots that exploit unique characteristics of biological cells and tissues for motion generation. Skeletal muscle tissue‐based bioactuators respond to externally applied stimuli, such as electrical fields. However, current bioactuation systems rely on open‐loop control strategies that lack knowledge of the actuator's state. The regulation of output force and position of biohybrid robots requires self‐sensing control systems that combine bioactuators with sensors and control paradigms. Herein, a soft, fiber‐shaped mechanical sensor based on a piezoresistive composite is proposed that efficiently integrates with engineered skeletal muscle tissue and senses its contracting states in a cell culture environment in the presence of applied electrical fields. After testing the sensor's insulation and biocompatibility, its sensitivity for typical strains (<1%) is characterized, and its ability is proven to detect motions from contractile skeletal muscle tissue constructs. Finally, it is shown that the sensor response can feed an autonomous control system, thus demonstrating the first proprioceptive biohybrid robot that senses and responds to its contraction state. In addition to inspiring implantable systems, biomedical models, and other bioelectronic devices, the proposed technology will confer biohybrids with decisional autonomy, thus driving the paradigm shift between bioactuators and intelligent biohybrid robots.