Doctoral student Shuo Li shakes hands with an optoelectronically innervated prosthesis. (Credit: Huichan Zhao)

Most robots achieve grasping and tactile sensing through motorized means, which can be excessively bulky and rigid. A group of researchers has devised a way for a soft robot to feel its surroundings internally, in much the same way humans do. The group has published a paper describing how stretchable optical waveguides act as curvature, elongation, and force sensors in a soft robotic hand.

The advent over the last 20 years of soft lithography and 3D printing has led to development of elastomeric sensors that are easily produced and incorporated into a soft robotic application. The group employed a four-step soft lithography process to produce the core (through which light propagates), and the cladding (outer surface of the waveguide), which also houses the light-emitting diode and the photodiode.

The more the prosthetic hand deforms, the more light is lost through the core. That variable loss of light, as detected by the photodiode, is what allows the prosthesis to “sense” its surroundings. Future work will focus on increased sensory capabilities, in part by 3D printing more complex sensor shapes, and by incorporating machine learning as a way of decoupling signals from an increased number of sensors.