https://www.youtube.com/watch?v=ZA8L9e0e2Qs
Research published in Scientific Reports describes a prototype of an unusual kind of robot based on the humble earthworm. This research is part of the field of 'soft robotics' – robotics based on squishy, deformable parts, rather than rigid parts with joints – and comes from the BioInspired Soft Robotics lab at the Italian Institute of Technology in Genoa, under Barbara Mazzolai.
Earthworms move with peristaltic motion: meaning that they expand and contract different parts of their bodies (called metameres) rhythmically to generate waves of force that propel them forward. The researchers describe how the alternately expanding-contracting chambers of the earthworm's body (called coeloms) maintain a constant volume as they contract – become shorter and thicker – and expand – become longer and narrower. The Italian researchers created soft actuators that mimic this constant-volume expansion-contraction cycle by pumping air in and out of a series of five robotic metameres, expanding when full of air, and then contracting. As an earthworm has bristles on its surface (called setae), which rub against the soil, creating the friction that propels the earthworm through the soil, the soft robot made by the Italian researchers has "passive setae-like friction pads".The prototype described in the paper is 45cm long and weighs 605 grams, and has demonstrated improved locomotion with a speed of 1.35mm/s, about 4.8 metres in an hour. This could lead to designs that could explore the world beneath our toes, scan for landmines or for earthquake victims buried in rubble, and even explore the subsurface of other planets and moons.