Spongey pads may one day let robots tweak the stiffness of their grasp

Mar 20, 2023

There's a tradeoff with robotic graspers – they're typically either firm enough to securely grab and lift sturdy, heavy objects, or soft enough to lift fragile objects without breaking them. A new sponge-based system, however, could allow one grasper to switch back and forth between doing both.

Developed by scientists at the University of Bristol, the setup is inspired by human fingers, which consist of hard bone surrounded by soft flesh. In the case of the grasping system, the two inside ends of a set of hard mechanical pincers are each covered by a spongey pad.

Each of those pads consists of a piece of silicone sponge material – much like the one you might use for washing dishes – which is encased in an airtight polymer skin. A silicone hose runs from the pad to an air pump.

When a soft touch is required, air is pumped into the pad, allowing to it expand to its full (and squishy) default thickness. When a firmer grasp is needed, air is drawn out of the pad. The resulting negative pressure temporarily compresses the sponge, making it thin and stiff.

It is hoped that the technology could ultimately allow existing industrial robots to perform tasks such as lifting and moving fragile items like eggs. It could also be applied to service robots which directly interact with people, reducing the likelihood of accidental injuries.

"We managed to use a sponge to make a cheap and nimble but effective device that can help robots achieve soft contact with objects," said the lead scientist, Dr. Tianqi Yue. "The great potential comes from its low cost and light weight."

Source: University of Bristol