A Multimodal Variable-speed Microrobot With Asymmetric Multilayer Structure for Moving Agility and Adaptability

Animals possess the capability to change locomotion modes while adjusting speeds to navigate complex terrains and quickly escape dangerous environments. However, integrating multimodal locomotion with variable speeds remains a critical challenge for soft microrobots. Here, we present an agile multimodal soft piezoelectric microrobot with variable speeds. The robot consists of an asymmetric multilayer structure composed of distributed passive layers to regulate robot motion modes. Based on the structure, the robot exhibits distinct locomotion modes and speed levels at different resonance frequencies. A prototype robot reaches 20.6 and 43.2 body lengths per second in two different modes, respectively, outperforming most reported multimodal soft robots and matching the agility of many animals. The robot also presents locomotion stability across a broad temperature range and robustness after compression. By switching the driving frequency, the robot achieves locomotion mode and speed transitions without reconfiguration, which endows the robot task-execution capability and adaptability in complex environments, including climbing a varying-gradient slope, enhancing carrying loads speed, escaping a trap, and traversing a wrinkled-paper canyon with rugged terrains. These results indicate that the asymmetric multilayer structure provides a solution for multimodal microrobots without additional complexity of fabrication and control.