How Can Interfacial Phenomena in Nature Inspire Smaller Robots

In nature, surfaces are evolutionarily designed to allow adaptation of species to their environments. Insects make extensive use of interfacial phenomena because of their small size and thus, large surface-area-to-volume ratio. This enables them to walk on different terrains, dive, swim, and adhere to surfaces in air and underwater. Moreover, they toggle between different interfaces, move in confined spaces, and overcome a wide range of obstacles. This progress report summarizes emerging directions in the field of bioinspired robotics with an emphasis on micro and nanoscale dynamic interactions. It is envisioned that interfacial phenomena will allow to miniaturize robots and increase the complexity of their operation. The key to success is the combination of functional surfaces, structural design and multiple modes of locomotion. For this to be realized, however, new paradigms are needed in terms of materials, fabrication, energy consumption, and actuation. This report discusses the development of small robots inspired by water striders, the bell spider, the leaf and ladybird beetles, backswimmers and cockroaches, among many others. It also discusses small soft robots inspired by roundworms, larvae, and parasites. From a broader perspective, fabrication of many small robots will enable to study collective effects and self-assembly, group behavior and swarming.