Researchers at Cornell University’s Organic Robotics Lab have developed a soft robot that uses stretchable optical waveguides that act as curvature, elongation and force sensors to feel its surroundings internally in the same way humans do.
In most robots today, the sensors are on the outside of the body and detect objects from the surface. In the robot developed by Cornell, the sensors are integrated into the body, so the robot detects forces being transmitted through the thickness of the robot in much the same way living organisms feel pain or other touch sensations.
Optical waveguides have been used since the early 1970s for sensing functions such as tactile, position and acoustic. Originally it was a complicated process but through soft lithography and 3-D printing, it has led to the development of elastomeric sensors that are easily produced and can be incorporated into soft robots, researchers say.
How They Did It
The Cornell group developed a four-step soft lithography process to produce the core (where light spreads) and the cladding—the outer surface of the waveguide—which also houses the light-emitting diode (LED) and the photodiode.
In the robotic hand as it deforms, light is lost through the core. This loss of light, as detected by the photodiode, is what allows the prosthetic hand 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,” says Robert Shepherd, assistant professor of mechanical and aerospace engineering at Organic Robotics Lab at Cornell. “The amount of loss is dependent on how it’s bent.”
Researchers used optoelectronic prosthesis to have the robot grasp and probe objects for shape and texture. For example, they had the robotic hand scan three tomatoes and determine, by softness, which was the ripest.
While this technology is a good fit for prostheses, it could be used in other industries as well, such as creating bio-inspired robots that could be used in space exploration.
In the future, the team plans to test optical waveguides in soft robotics that will focus on increased sensory capabilities by 3-D printing more complex sensor shapes and incorporating machine learning.