Controllable Self-Propulsion of a Biohybrid Millirobot Through Muscle-Fiber-Alignment Programming and Magnetically Assisted Steering

Biohybrid robots with autonomous motility can recapitulate existing biological structures and interact with their surroundings, attracting broad attention from researchers regarding their locomotion characteristics. However, muscle-driven biohybrid millirobots often struggle to maintain stable and tunable locomotion beyond obstacle-free fluidic environments, thereby limiting their applicability in task-oriented operations such as trajectory-specific directional modulation and cargo transport. To address this issue, we developed a muscle-driven biohybrid thin-film millirobot (MBF‑Robot) by patterning cardiomyocytes onto a flexible thin-film substrate in distinct spatial arrangements. This design allows MBF‑Robots with identical geometrical configurations to exhibit distinct propulsion modes and motion directions, with a maximum speed of 0.79 mm/s (1 Hz). Moreover, by incorporating a small quantity of Fe₃O₄ particles into the robot's structural body, we implemented a synergistic control strategy that integrates inherent muscle-driven propulsion with non-contact directional regulation via an external magnetic field. This approach, while retaining muscle actuation as the sole driving force, imparts the MBF‑Robot with continuous, rapid, and reversible navigation capability. Consequently, the MBF‑Robot successfully executed tasks such as microsphere transport along prescribed trajectories and selective control of multiple millirobots. Overall, this work establishes a design paradigm and engineering foundation for achieving controlled locomotion in biohybrid millirobots.