Active matter, curved spaces: Mini robots learn to 'swim' on stretchy surfaces

While many of these interactions happen through direct contact, like the concert-goers' nudging, some interactions can transmit through the material the objects are on or in -- these are known as indirect interactions. For example, a bridge with pedestrians on it can transmit vibrations, like in the famous Millennium Bridge "wobbly bridge" instance. While the results of direct interactions (like nudging) are of increasing interest and study, and the results of indirect interactions through mechanisms like vision are well-studied, researchers are still learning about indirect mechanical interactions (for example, how two rolling balls might influence each other's movement on a trampoline by indenting the trampoline's surface with their weight, thus exerting mechanical forces without touching). Physicists are using small wheeled robots to better understand these indirect mechanical interactions, how they play a role in active matter, and how we can control them. Their findings, "Field-mediated locomotor dynamics on highly deformable surfaces" are recently published in the The Proceedings of the National Academy of Sciences (PNAS).