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Robotic gripper conforms to objects of any shape and fragility

02 February 2016

EPFL Scientists have developed a soft robotic gripper made from rubber and stretchable electrodes that can bend and pick up delicate objects like eggs.

The soft gripper uses 'electro-adhesion': flexible electrode flaps act like a thumb-index gripper that can pick up fragile objects of arbitrary shape and stiffness, like an egg, a water balloon or paper.

"This is the first time that electro-adhesion and soft robotics have been combined together to grasp objects," says Jun Shintake, a doctoral student at EPFL and first author of a paper describing the work in the journal, Advanced Materials.

When the voltage is turned on, the electrodes 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 it with electrostatic forces in the same way that a balloon sticks to a wall. These electrodes can carry 80 times their own weight and require no prior knowledge about the object's shape.

The electrode flaps consist of five layers: a pre-stretched elastomer layer sandwiched between two layers of electrodes, plus two outer layers of silicone of different thickness. With no voltage applied, the difference in thickness of the outer layers makes the flaps curl outwards. When a voltage is applied, the attraction between the two layers of electrodes straightens out the membranes. This straightening of the membranes from a curled position mimics muscle flexing.

At the tips of the flaps, the electrodes of each layer are designed for optimal electrostatic grip. These 'inter-digitated' electrodes, which look like two combs fitted together, create an electrostatic field that produces the electro-adhesion phenomenon.

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