X-muscle actuator with selective regional contraction for a biohybrid rotatable joint

Biohybrid robots that utilize selective regional contraction of skeletal muscle have potential for achieving diverse movements, yet they face challenges such as insufficient spatial utilization and integration. In this study, an X-muscle actuator (XMA) was developed to address these issues. Using skeletal muscle cells, the XMA was designed with regional response characteristics and uniform contraction capability. The performance of the XMA was characterized, with maximum active contractile force reaching 2.97 mN. A biohybrid rotatable joint, integrating the XMA with mechanical structures, achieved a maximum unidirectional rotation angle of 1.39° under electrical stimulation, and multi-directional movements were realized through composite stimulation. This work not only enhances the movement diversity of biohybrid robots but also establishes a new paradigm for combining intrinsic biological tissue properties with advanced mechanical design, laying the foundation for the next generation of higher-performance, more versatile biohybrid systems.