Moving an arm to grasp an object, for instance, involves sensors in the elbow and arm that provide precise feedback on speed, location and force. As the fingers contact the object, skin deforms, providing precise information about position and force while cushioning the object. In addition, human muscles can be moved very accurately because they operate in dynamic tension - one muscle always pulling against another. Calvert and his students already have built a prototype synthetic muscle made from two polymer layers. One layer contracts strongly when an electric field is applied and the other acts like a sponge.
Water is transferred between the layers and the muscle works like a hydraulic jack.
So the system functions by changing shape without changing volume. Similar synthetic muscles made from gel change volume because they take up and expel water. Now he hopes to take the work to a smaller scale. We want to have a drop of this polymer with little electrodes to make a very small muscle that could be used to move a device on a printed circuit board, such as a tiny valve or a mirror to reflect a laser beam. Polyacrylic acid is the component that contracts.