As anyone who has grown climbing plants will know, the things are great at grasping onto thin objects such as strings or bamboo poles. A new robotic gripper, inspired by such plants, could find use in the handling of small, delicate items.
"Twining plants" work by sending out touch-sensitive tendrils that wrap themselves around whatever they encounter. Developed by a team at the University of Georgia, the new gripper incorporates a similar mechanism.
"We had tried different designs but we were not happy with the results, then I recalled the pole beans I grew in our garden few years ago," says the lead scientist, Assoc. Prof. Mable Fok. "This plant can hold onto other plants or rope so tightly. So, I did some research on twining plants and thought it was a good design from nature for us to explore."
The resulting 3D-printed prototype device has a plant-tendril-like cylindrical elastic body made of silicone rubber, with an elastic spine (basically a rubber tube) running lengthwise inside of it. That spine in turn has a fiber optic sensor at its core, and is encircled by an air-filled pneumatic channel running along its length. The channel winds around the spine, in the same manner that a twining plant's tendril winds around a string.
When the fiber optic sensor detects that the gripper is in contact with an object, it prompts an attached miniature compressor to pump air into the channel surrounding the spine. This causes the gripper to twist like a corkscrew, winding itself around the object in the process.
Importantly, the sensor is also able to determine the diameter of the object, and the angle of the twist. It adjusts the amount of air being pumped into the pneumatic channel accordingly, determining how tightly the gripper winds around the object – the higher the air pressure, the tighter the twist. Once the grasping task is complete, lowering the pressure causes the gripper to straighten back out and release the item.
"Our robot’s twining action only requires a single pneumatic control, which greatly simplifies its operation by eliminating the need for complex coordination between multiple pneumatic controls," says Fok. "Since we use a unique twining motion, the soft robotic gripper works well in confined areas and needs only a small operational space."
The device has already been used to handle objects such as pencils, paintbrushes and even a straightened wire paper clip. It is hoped that the technology may ultimately find use in tasks like handling delicate plants, grasping samples in fragile glass tubes, and performing robotic surgery.
A paper on the research was recently published in the journal Optics Express.
Scientists in Italy have also developed a plant-tendril-inspired robotic device, although theirs incorporates an ion-containing liquid that responds to an electrical current.
Source: University of Georgia
