Biohybrid Muscle Actuator with Embedded Spring-Shaped Skeleton for Multimodal Elephant Trunk-Like Motion

We present a biohybrid muscle actuator integrated with an embedded spring-shaped skeleton to achieve multimodal, elephant trunk-like bending motion. The skeleton's ability to bend at any position due to its spring-like structure enables spatially selective deformation through localized electrical stimulation. Muscle tissue cultured around the skeleton formed aligned myotubes along its longitudinal axis, resulting in a structurally unified muscle actuator without the need for additional assembly. Experiments demonstrated controllable, site-specific bending responses and synchronized actuation. Furthermore, a soft gripper composed of two muscle actuators successfully grasped and dragged objects at a speed of 2.2 mm/s. This approach provides a promising strategy for flexible and functional biohybrid soft robotic systems.