Presented by:

October 17, 2018      

Researchers have developed a new mechanical system for prosthetic hands that are strong enough to crush a can, and reactive enough to catch a ball.

The technology, developed by researchers from Cornell University and the University of Pennsylvania, is smaller and less expensive than motors that control most prosthetic fingers in existence today. The research is highlighted in a new article in the latest issue of journal Science Robotics, published by the non-profit science society AAAS.

Robotic Grippers Prosthetic Hands

Credit: O’Brien et al., Sci. Robot. 3, eaau5543 (2018)

From the article:

The grip strength, grasping speed, and diversity of motions of even the most advanced prosthetic hands pale in comparison with those of a human hand. User studies have shown that 90% of patients with prostheses consider their hand too slow and 79% consider it too heavy. As such, engineering simpler designs for robotic hands without sacrificing adequate precision, force, and speed remains a challenge.

Kevin O’Brien and colleagues tackled this problem by creating a cylindrical pulley system comprised of belts wrapped around wheel-shaped gears (often used in motor vehicle mechanics). The resulting cylinders, dubbed elastomeric passive transmissions (EPTs), could fine tune the grasping force and speed of contact with an object on demand by adjusting the tension in a wire spooled around wheels controlling the cylinders’ movement.

The engineers used EPTs to construct an entirely 3-D printed prosthetic hand, which demonstrated a nearly threefold increase in grip force while still maintaining fast finger closing speeds (in seconds) compared to rigid spools. Weighing about as much as a human hand, the prosthetic was able to hold heavy objects such as a wrench.

Researchers said EPTs could be applied to other devices, such as robotic tendons, soft exosuits, and bio-inspired mobile robots.