Researchers develop a soft robot with a human touch

For the most part, robots are developed with motors. These robots can grip and achieve tactile sensing through these somewhat bulky and rigid mechanism. However, a group of researchers at Cornell University have designed a new way for soft robots to feel. The robot can sense its surrounding internally, similarly to the way humans do.

(A) Schematic of hand structure and components; (B) image of the fabricated hand mounted on a robotic arm with each finger actuated at ΔP = 100 kPa.

In a published paper, Robert Shepherd, assistant professor of mechanical and aerospace engineering and principal investigator of Organic Robotics Lab, describes how stretchable optical waveguides act as curvature, elongation and force sensors in a soft robotic hand.

“Most robots today have sensors on the outside of the body that detect things from the surface,” Huichan Zhao, a doctoral student and lead author of “Optoelectronically Innervated Soft Prosthetic Hand via Stretchable Optical Waveguides,” explains.

“Our sensors are integrated within the body, so they can actually detect forces being transmitted through the thickness of the robot, a lot like we and all organisms do when we feel pain, for example,” he adds.

Optical waveguides have been in use since the early 1970s for numerous sensing functions, including tactile, position and acoustic. The development of these processes have been somewhat cumbersome. However, with the rise of soft lithography and 3D printing, elastomeric sensors can be easily produced and incorporated into a soft robotic application.

Shepherd’s 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 LED (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.

“If no light was lost when we bend the prosthesis, we wouldn’t get any information about the state of the sensor,” Shepherd said. “The amount of loss is dependent on how it’s bent.”

The group used its optoelectronic prosthesis to perform a variety of tasks, including grasping and probing for both shape and texture. Most notably, the hand was able to scan three tomatoes and determine, by softness, which was the ripest.

www.cornell.edu