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Soft gripper can pick up fragile objects of almost any shape

03 February, 2016

Swiss researchers have developed a flexible gripping technology that can bend to pick up delicate objects such as eggs and paper without needing to know anything about the type of object or its shape. It could, for example, be used to handle food, to capture debris in outer space or be incorporated into humanoid robots.

The soft grippers – made from rubber and containing stretchable electrodes – combine two technologies: artificial muscles and electroadhesion.

The grippers consist of a pair of flexible flaps that incorporate electrodes. When a voltage is applied, the electrodes bend towards the object to be picked up, imitating the way that muscles work. The ends of the electrodes act like fingertips that conform gently to the shape of the object, gripping onto it with electrostatic forces in the same way that an electrostatically charged balloon sticks to a wall. The electrodes are claimed to be able to carry up to 100 times their own weight and need no prior knowledge about the object's shape.

“This is the first time that electroadhesion and soft robotics have been combined together to grasp objects,” says Jun Shintake, a doctoral student at the Ecole Polytechnique Fédérale de Lausanne (EPFL), and lead author of a recently published paper describing the new gripper.

Other soft gripping technologies either rely on pneumatic control or cannot pick up fragile objects if they have not been told beforehand about the object's shape. They are also incapable of handling flat or deformable objects.

EPFL researcher Jun Shintake with the new gripper

“The novelty of our soft gripper is the ideal combination of two technologies: artificial muscles and electroadhesion,” says Dario Floreano of EPFL. The “unique” configuration of electrodes and silicone membranes allows the new technology to control the bending of the flaps and the electrostatic grip.

The flaps consist of five layers. At the centre is a pre-stretched elastomer layer sandwiched between two layers of electrodes. There are two outer layers of silicone of different thickness. When the voltage is off, the difference in thickness between the outer layers makes the flaps curl outwards. When the voltage is applied, the attraction between the two electrode layers straightens the membranes from the curled position, mimicking the flexing of muscles.

At the tips of the flaps, the electrodes of each layer have been designed for optimal electrostatic grip. The electrodes, which look like a pair of combs fitted together, create an electrostatic field that produces the electroadhesion effect.

The EPFL research has been funded by the Swiss national robotics organisation, NCCR Robotics

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