A team of scientists at the University of Pennsylvania's School of Engineering and Applied Science has come up with a way of dramatically increasing the strength of soft-robotic devices through a novel clutch design — and hope to use it to build wearables for physical feedback in virtual and augmented reality.
"Our approach tackles the force capacity of clutches at the model level," explains James Pikul, assistant professor and co-corresponding author on the paper. "And our model, the fracture-mechanics-based model, is unique. Instead of creating parallel plate clutches, we based our design on lap joints and examined where fractures might occur in these joints. The friction model assumes that the stress on the system is uniform, which is not realistic. In reality, stress is concentrated at various points, and our model helps us understand where those points are. The resulting clutch is both stronger and safer as it requires only a third of the voltage compared to traditional clutches."
These clutches, the team has proven, dramatically increase the strength of soft-robotic devices — offering 63 times more force capacity per unit of electrostatic force, when compared with rival state-of-the-art electroadhesive clutches. Once assembled into a soft robotic finger, the result is a device 27 times stronger than one without electroadhesive — boosting its load carrying capabilities to the point it can hold four pounds, or roughly the weight of a bag of apples.
The team isn't just focusing on apple carrying, though: the clutch's ability to work at 125V, considerably less than rival designs, means it's safer for use in wearable robotics — including force-feedback systems for virtual and augmented reality. "Traditional clutches require about 300 volts, a level that can be unsafe for human interaction," explains first author David Levine. "We want to continue to improve our clutches, making them smaller, lighter, and less energetically costly to bring these products to the real world. Eventually, these clutches could be used in wearable gloves that simulate object manipulation in a VR environment."
"Current technologies provide feedback through vibrations, but simulating physical contact with a virtual object is limited with today’s devices," adds Pikul. "Imagine having both the visual simulation and feeling of being in another environment. VR and AR could be used in training, remote working, or just simulating touch and movement for those who lack those experiences in the real world. This technology gets us closer to those possibilities."
The team's work has been published under closed-access terms in the journal Science Robotics.