New robotic gripper can handle delicate objects

Scientists have developed a new soft robotic gripper that can pick up fragile objects of different shapes and stiffness, like an egg, water balloons or paper.
The lightweight gripper may soon be handling food for the food industry, capturing debris in outer space or incorporated into prosthetic hands.
It uses electroadhesion - the electrostatic stickiness that causes a balloon rubbed in your hair stick to a wall, researchers said.
"This is the first time that electroadhesion and soft robotics have been combined together to grasp objects," said first author Jun Shintake, doctoral student at EPFL (Ecole Polytechnique Federale de Lausanne) in Switzerland.

When the voltage is turned on, flexible electrode flaps, that act like a thumb-index duo, bend towards the object to be picked up, imitating muscle function.
The tip of the electrodes act like fingertips that gently conform to the shape of the object, gripping onto it with electrostatic forces in the same way that the balloon sticks to the wall.

These electrodes can carry 80 times its own weight and no prior knowledge about the object's shape is necessary.
In comparison, other soft grippers are either pneumatically controlled or fail at picking up fragile objects without telling the gripper beforehand about the object's shape. They also have been unable to handle flat or deformable objects.

"The novelty of our soft gripper is the ideal combination of two technologies - artificial muscles and electroadhesion," said Dario Floreano of EPFL.
"Our unique configuration of electrodes and silicone membranes is what allows us to control the bending of the flaps and the electrostatic grip," said Herbert Shea of EPFL.
The electrode flaps consist of 5 layers - a pre-stretched elastomer layer sandwiched between two layers of electrodes, plus two outer layers of silicone of different thickness.
When the voltage is off, the difference in thickness of the outer layers makes the flaps curl outwards.
When the voltage is on, the attraction between the two layers of electrodes straightens out the membranes.

This straightening of the membranes from a curled position mimics muscle flexion.
At the tips of the flaps, the electrodes of each layer are designed for optimal electrostatic grip.
These interdigitated electrodes, which look like two combs fitted together, create an electrostatic field that causes electroadhesion.
The research was published in the journal Advanced Materials.