The latest example of this is a highly efficient "Squidbot" developed by engineers at the University of California (UC) San Diego that uses a combination of soft and rigid materials to propel itself through the water much like the real thing.

The team's squid-inspired robot is shaped like a paper lantern and is designed to store elastic energy inside its skin and a set of flexible ribs as it takes in water. The ribs are anchored to a pair of circular plates at either end of the body, one drawing in surrounding water via a nozzle and also ejecting it as the soft body contracts.

This action produces jet pulses that propel the robot through the water, much like a natural squid. In effect, this means the Squidbot is able to carry its power source within its body, eliminating the need for a tether. The scientists behind the machine believe it is the first of its kind.

"Essentially, we recreated all the key features that squids use for high-speed swimming," says Michael T. Tolley, a professor in the Department of Mechanical and Aerospace Engineering at UC San Diego. "This is the first untethered robot that can generate jet pulses for rapid locomotion like the squid and can achieve these jet pulses by changing its body shape, which improves swimming efficiency."

Another advantage of the design is that the second plate can be loaded up with a sensor or camera to carry out underwater monitoring tasks. Soft robots of this type could find uses in environmental research projects aimed at conserving fish and coral, which could otherwise be damaged by robots with stiffer bodies.