Tetanus-driven biohybrid multijoint robots powered by muscle rings with enhanced contractile force

Biohybrid actuators using muscle rings have been limited to twitching movements and are unsuitable for sustained contractile force applications. In this study, we developed muscle rings capable of generating high contractile forces under tetanus stimulation. By enhancing the rigidity of pillar-shaped supports and increasing myoblast density through reduced extracellular matrix, we promoted the formation of dense, well-aligned muscle fiber bundles. The optimized muscle rings exhibited higher contractile forces compared to traditional methods. Integrating these muscle rings with C-shaped anchors efficiently converted contractile force into bending motion. We demonstrated the application of these muscle rings in gripper- and slither-type biohybrid robots, achieving large deformation and undulatory movement. This work advances biohybrid robotics by enabling sophisticated movements requiring continuous and powerful muscle contractions.