Abstract
Limited muscle force generation remains a major bottleneck in developing stronger, faster, and more efficient biohybrid robots. We present a fully autonomous self-training platform that strengthens skeletal muscle tissues by harnessing their robust spontaneous contractions. This approach produced muscle actuators with a maximum force of 7.05 mN and a stress of 8.51 mN/mm(2), the highest reported for C2C12-derived muscle actuators. To demonstrate their capabilities, we developed a twin-tail muscle-powered ostraciiform swimming robot, OstraBot, and guided its design using a physiology-based muscle contraction model. Model-informed analysis identified stiffness-frequency combinations that maximized muscle energy output, enabling a top speed of 467 mm/min (15.6 body lengths/min), significantly outperforming previously reported skeletal muscle-powered biohybrid robots. The robot demonstrated strong thrust generation and precise on-off controllability through sound-triggered clapping control. This work establishes a versatile platform for producing high-strength skeletal muscle actuators and quantitatively guiding the robotic design for high-performance biohybrid robots.