The UC-Softhand is composed of soft fingers, two twisted string actuators, and a third actuator for rotating the thumb.  It is the lightest prosthetic hand prototype with 3 actuators that have been developed in the world so far. A twisted string actuation mechanism is composed of two twisted cords that trasnform the rotational motion of an electrical motor into high linear forces. It is an extremely light-weight and low cost  system. However the contraction ratio of the twisted string system is low, typically around 20%.

The good news is that by taking an innovative approach and by going to an over twisting phase we managed to  reach to a contraction ratio of 80%. In addition, we designed the system to be non-backdrivable. That is actuators can be turned off after forming a grasp,. This enables the hand hold its form without consuming energy.

The UC-Softhand is fabricated by a 3D printer. It has a human hand size, and weights only 280g, 30 percent lighter than the average human hand. We have developed and miniaturized dedicated electronics that can be embedded in the palm of the hand.