Soft grippers are everywhere in nature. Elephant trunks, lizard tongues, octopus arms and human hands are just a few of the biological innovations capable of grasping and manipulating delicate objects.

Yet giving a robot a gripper or pincher capable of that same dexterity is a significant challenge, particularly if you want to do it using only soft materials, which Wanliang Shan does. His research focuses on soft robotics, a rapidly emerging field in which researchers are developing robots made entirely out of soft materials like elastomers and gels. These soft-bodied bots have a number of advantages over their rigid counterparts, especially when it comes to grasping objects, which may be soft, slippery or delicate.

Now, Shan has developed a programmable pneumatic soft-gripper capable of picking up and manipulating delicate objects, potentially in manufacturing and cooperative service settings where compliance, speed and dexterity are key.

"This work for the first time introduces an entirely soft gripper that mimics the appearance and functionality of a human hand, including grasping, twisting and releasing of various objects," said Shan, an assistant professor of mechanical engineering. "The use of smart materials made possible a simple design and a scalable fabrication process."

Smart materials give gripper human-like dexterity

Shan's soft gripper is innovative in its design methodology and materials. The gripper uses three pneumatic fingers powered by a single air pressure regulator, eliminating the need for a complicated set of tubes and valves used in existing gripper designs. Electrically stimulated ligaments within the machine's three fingers allow the gripper to lift, twist or drop a variety of objects.

The ligaments, which have a range of stiffness similar to that of a human muscle, use a material Shan developed that can change its rigidity rapidly, giving the soft gripper the ability to alternately grasp and release objects with a 15-second response time.

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The research, which was conducted by Shan and three graduate students, has been accepted for publication in Soft Robotics. Now, the team plans to improve the responsiveness of the activation by designing new smart materials, as well as integrate more sensing and actuation mechanisms to the fingers of the gripper.

"Ultimately, we will have a robotic hand that can do exactly what a human hand can do and even more. That is our ultimate goal," Shan said.