Bio‐Inspired Flex‐Rigid Design Enabling High‐Performance Multimodal Locomotion of Robots

ABSTRACT

Biological locomotion often benefits from flex‐rigid architectures, where soft tissues coordinate with rigid skeletons or appendages to enable effective force transmission, versatile motion generation, and environmental adaptability. However, translating this paradigm to robotics remains challenging. Here, we present a bio‐inspired flex‐rigid robot (Bio‐FRR) that integrates a muscle‐like pneumatic actuating unit with a fin‐like rigid arched plate to achieve high‐performance multimodal locomotion. Unlike conventional rigid‐flexible hybrid robots in which rigid elements mainly serve as passive reinforcements or fixed appendages, the Bio‐FRR employs a deployable flex‐rigid mechanism, where a multi‐chamber pneumatic actuator actively drives rigid arched plates to fold and unfold, thereby converting local soft deformation into body‐level posture reconfiguration and locomotion‐relevant mechanical output. Such a design endows the Bio‐FRR with versatile and adaptive locomotion across various environments, realizing five high‐performance locomotion modes on land and in water without structural reconfiguration, including upright hopping, leapfrogging, terrestrial crawling, diving, and swimming. The Bio‐FRR reaches a maximum terrestrial speed of 1.23 body lengths per second (BL/s), a horizontal swimming speed of 0.42 BL/s, and an untethered driving speed of 48.67 mm/s. Bio‐FRR offers a robust blueprint for next‐generation amphibious soft robots, enabling versatile locomotion and enhanced adaptability.