Locomotion for Insect-Scale Robots With Bionic Strategies: A Review

Insect-scale robots possess the advantageous traits of small size, lightweight, and high flexibility. These features make them suitable for complex, narrow, or higher-than-the-ground environments, allowing these insect-scale robots to become highly sought-after research topics. However, the miniaturization of robots has brought challenges to improving their environmental adaptability, such as climbing and obstacle-crossing abilities. Mainstream strategies inspired by natural creatures to address these challenges can be classified into two types: adhesion for climbing robots and multi-motion modes for obstacle-crossing robots. Adhesion is preferred for occasions requiring climbing slopes, walls, or ceilings. In contrast, multi-motion modes are suitable for occasions with limited obstacle heights or complex terrains to enable miniaturization and cable-free operation. This paper summarizes the current research on environment-adaptable insect-scale robots (EAISRs) with adhesion or multi-motion modes. Then, the paper discusses the advantages, disadvantages, and application scenarios of EAISRs, including climbing robots with different adhesion strategies and obstacle-crossing robots with various driving methods in detail. Finally, this paper proposes the future challenges and possible solutions for EAISRs, providing ideas for future interactions between insect-scale robots and the environment.