May 29 2015
Stanford engineers have created an adhesive material inspired by the unique properties of grippy gecko fingertips, which could enable robotic hands to hold nearly any kind of object by applying less pressure.
David Christensen, a mechanical engineering graduate student at Stanford, observed an extremely grippy thin scrap while trimming a piece of adhesive inspired by gecko fingertips. He shared this with his colleague Elliot Hawkes, who laminated a piece of non-stretchable yet flexible film on the back of the scrap. They observed that when combined, the grip was greatly improved, and some distinct properties resulted.
Biomimetic Dexterous Manipulation Laboratory.
Grasping without Squeezing -- Super Friction Gripper
A material inspired by the unique physics of gecko fingertips could allow robotic hands to grip nearly any type of object without applying excessive pressure
Biomimetic Dexterous Manipulation Laboratory.
Gecko Tape Magic Trick
Demo of gecko tape gripper in action.
"The first time we played with the composite, it was clear the material grabbed onto textures that we were never able to grip before, but doesn't remain stuck," said Christensen, who is advised by Mark Cutkosky, a professor of mechanical engineering.
Another fellow graduate student, Hao Jiang, illustrated the ability of the film to tightly grip to any textured surface effortlessly. As a result, they used the adhesive film for a robotic grabber they were working on.
The trio, in collaboration with Cutkosky's lab engineers, developed a gripping mechanism that can pick up objects of any size, texture or shape, right from trash bins to balloons to burritos, without deforming them.
The work will be presented by Hawkes at the IEEE International Conference on Robotics and Automation to be held this week in Seattle. The project was nominated for both the Best Paper and Best Student Paper awards.
"What makes this gripper different is that it doesn't need to squeeze objects to pick them up, since the material grips without pressing it into the surface," Hawkes said.
It is the first adhesive mechanism which is independent of any kind of pressing or pulling force. The students and Cutkosky work on designing adhesive materials that imitate the small hair-like structures on gecko toes, which allow the animal to move on almost any surface.
The bottom part of the fabricated adhesive material includes a number of tiny hairs which are each 100 µm long. In an upright state, the hairs tend to contact with the objects without grabbing onto them. However, when the mechanism tugs on the film, it holds on to the object with the hairs flattened to make contact with the object.
Upon releasing the tension on the film, the hairs stand upright again, which makes the material non-sticky, thereby releasing the object.
"You can think of it basically like gripping with 'super friction' that's so strong that you don't need to actually squeeze to get friction," Christensen said. The tiny hairs enable the gripper to cling on to nooks and corners of uneven surfaces or comfortably fit to any smooth surface.
The team has tested the adhesive film on a wide range of handheld objects from telephone receivers to basketballs, footballs, large pipes and water-filled bags. It can easily carry objects that weigh several pounds. However, Jiang said that the physics of the system indicate that it would be possible to grab larger objects with a larger gripper.
"Seeing this material in action is really surprising. Using a glove with this material, a child could palm a basketball, but could still toss an air-filled balloon without having it stick. It's super-grippy, but not sticky at all," Hawkes said.
The team is now planning to develop the material into a more complete robotic hand with a wide range of anticipated applications, such as industrial uses, around-the-home robotics or prosthetics, as well as focusing on the handling of delicate objects.