Reflexes turn active metamaterials into robots

Materials composed of energy-generating constituents such as active matter and distributed robots are promising platforms to create autonomous functional materials. However, the control of such materials is typically achieved using feed-forward schemes, which do not work well in unpredictable environments and in under-actuation scenarios. Here, we introduce active metamaterials with a minimal feedback control that both exhibit unusual non-reciprocal responses and display adaptable and autonomous robotic locomotion. Inspired by reflex actions in animals and robots, we create metamaterials with translation-invariant reflex control, in which the active forces exerted are dependent on strains at neighboring sites. We demonstrate experimentally that these odd elastic materials are able to roll or crawl uphill and in complex terrains. Integrating reflexes in metamaterials opens avenues towards animate matter with autonomous, adaptable and interactive functionalities.