And while most of them have been produced in labs utilizing high-tech materials, a new type could be made by hobbyists using a 3D printer.

Known as GRACE (GeometRy-based Actuators able to Contract and Elongate) the pneumatic actuating system was designed by scientists at the Istituto Italiano di Tecnologia (IIT, Italian Institute of Technology) and the Scuola Superiore Sant'Anna (SSSA, Sant'Anna School of Advanced Studies).

Each actuator takes the form of a flexible hollow plastic bulb with pleats running along its sides. When air is pumped into the actuator via a connected hose, it contracts longitudinally while expanding radially – in other words, it gets shorter and fatter. When air is withdrawn, on the other hand, the actuator gets longer and skinnier.

Therefore, if incorporated into a robotic finger (as an example), an actuator could pull the finger closed when air was pumped in, and extend it straight when air was withdrawn.