Recent Advances in Electrically Actuated Functional Materials for Microrobot Locomotion
Electrically actuated microrobots, typically defined as devices under 5 cm in length and 5 g in mass, offer distinct operational advantages over thermally, magnetically, or optically driven counterparts, particularly at the centimeter scale where external field-generation hardware imposes prohibitive cost and redundancy. This review systematically examines the intrinsic coupling mechanisms between the electromechanical performance parameters of functional materials and the resulting locomotion modes of microrobots. The central premise is that material-level electromechanical properties—actuation strain, blocking force, energy density, and drive voltage—directly govern critical system-level capabilities including obstacle-crossing ability and energy efficiency. The authors analyze how distinct material classes, such as dielectric elastomers, piezoelectric ceramics, and shape-memory alloys, map to specific locomotion modalities, thereby delineating the current performance boundaries of the field. The review identifies that power supply and control strategy remain the two dominant bottlenecks limiting autonomous operation and long-duration mission execution. By establishing a direct correlation between material selection and locomotion performance, this work provides a structured framework for researchers to set research directions and performance targets. The analysis concludes with a summary of challenges and future trends, emphasizing the need for materials that simultaneously satisfy low drive voltage, high strain, and high power density requirements for real-world deployment in unstructured environments.