Making Soft Robots Stronger with a New Electro-Adhesive Clutch

Making soft robots stronger and safer and making virtual reality gloves feel more real

Soft robots, or ones constructed of materials such as rubber, gels, and linen, offer benefits over their tougher, heavier counterparts, particularly in activities requiring a direct human connection. Robots that could securely and gently assist persons with restricted mobility with grocery shopping, food preparation, dressing, and even walking would be life-changing.

However, soft robots presently lack the strength required to execute such jobs. Making soft robots stronger without losing their capacity to interact with their surroundings has long been a difficulty, limiting the progress of these technologies. With the link between strength and softness in mind, a team of Penn Engineers developed a new electro-adhesive clutch. Soft robots with a new electro-adhesive clutch allow them to grip 4 pounds, 40 times more than the hand could lift without the clutch. Furthermore, the capacity to complete this duty, which required both a delicate touch and strength, was accomplished with only 125 volts of electricity, which is one-third of the voltage necessary for present virtual reality clutches.

Their low-power and safe technique might also allow for wearable soft robotic devices that imitate the experience of handling a tangible object in augmented and virtual reality settings.

The School of Engineering and Applied Science's James Pikul, assistant professor in mechanical engineering and applied mechanics (MEAM), Kevin Turner, professor and chair of MEAM with a secondary appointment in materials science engineering, and their Ph.D. students, David Levine, Gokulanand Iyer, and Daelan Roosa, published a study in Science Robotics describing a new, fracture-mechanics-based model of electro-adhesive clutches, a mechanical structure.

"Our technique addresses clutch force capacity at the model level," adds Pikul. "And our model, based on fracture mechanics, is unique." Instead of designing parallel plate clutches, we focused on lap joints and investigated where fractures may occur. The friction model presupposes uniform stress on the system, which is unrealistic. In reality, stress is concentrated at different points, and our model assists us in determining where those points are. The resulting clutch is both stronger and safer, requiring only one-third the voltage of traditional clutches."