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A Strong Robot Hand with a Softer Side

A robotic gripper that combines strength with delicacy could help drones hold packages or industrial robots sort objects.
February 9, 2016

A robotic gripper invented at the École Polytechnique Fédérale in Lausanne, Switzerland, is gentle enough to pick up an egg or a single piece of paper, yet strong enough to carry 80 times its own weight. It demonstrates a promising new approach to robotic manipulation that could help machines take on more dexterous tasks.

The EPFL team built a proof-of-concept gripper made of two soft rubber flaps. It uses electroadhesion to get a firm grasp. When an electrical current is applied, the flaps become oppositely charged and bend inward. This can also cause the flaps to be attracted to—and adhere to—nearby objects.

The rubber material and electroadhesion force are gentle enough to prevent even water balloons from bursting. The flaps also act fast, taking about 200 microseconds to react to the electrical current—literally faster than the blink of an eye.

The gripper is the first to combine soft robotic parts with electroadhesion and sensors that allow the robot to monitor itself, according to Jun Shintake, the paper’s lead author and an EPFL researcher. It would be a welcome alternative to the custom robotic hands or complicated sensor arrays and software that currently allow robots to pick up objects of specialized and varying shapes.

“A key advantage of soft robotics is that they are safe and effective for interacting with humans, and this makes them ideal for adapting with humans and their environments,” says Conor Walsh, a robotics researcher and faculty member at the Harvard Wyss Institute for Biologically Inspired Engineering. “In this case, the gripper is soft and compliant and can nicely conform to object shapes when actuated, but then also has the nice added feature of active adhesion.”

The applied electricity courses through electrodes embedded in the gripper’s flaps. The electrodes are arranged to create the maximum possible electric field, allowing for an electroadhesive effect 10 times higher than if the electrodes were placed in a conventional manner.

As a result, the gripper can pick up items that weigh more than 80 times its own weight (the two-flap version built at EPFL weighs 1.5 grams). That could make it useful for warehouse or manufacturing tasks (see “Amazon Robot Contest May Accelerate Warehouse Automation”), or perhaps even for delivery drones, as it would add very little weight while still allowing a drone to carry relatively large objects.

Shintake believes the gripper also has promise for object manipulation in space, or for sorting items in the food industry.

“I would like to emphasize the adaptability of our gripper,” Shintake says. "The gripper is not the only shape we can achieve. It can be designed with three fingers or five fingers, and changing the size is no problem."

The technology could be especially useful in humanoid robots or prosthetics, which are expected to perform tasks more suited to the most advanced grippers of all: human hands. Combining a gripper with smart skin that can sense pressure could give rise to even more intelligent options (see “An Artificial Hand with Real Feelings”).

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