Robots such as those used in factories are often equipped with vacuum grippers, for holding onto flat objects. Typically, those grippers are powered by compressed air, which has some drawbacks. Now, however, scientists have developed one that instead utilizes an artificial muscle.
The problems with air-powered vacuum grippers include the facts that the required compressors are noisy, they use a lot of energy, plus they're big and bulky. That's where the new gripper comes in.
Developed by a team from Germany's Saarland University led by Prof. Stefan Seelecke, it incorporates bundles of ultrafine shape memory wires. Arranged in a circle, these bundles are attached to one side of a thin metal disc that can pop up or down, going concave or convex. The disc is in turn attached to a circular rubber membrane on the other side, for forming a seal against flat surfaces.
When an electrical current is run through the nickel-titanium alloy wires, they warm up. This causes their inner lattice-like structure to change in such a way that they temporarily become shorter. When that current ceases, they instantly cool back down and return to their previous longer form.
In this way, they act like muscle fibers that contract and relax, with the circle of wire bundles acting like one complete muscle. By switching on and off the electrical current that flows to that muscle, it either contracts or relaxes. This causes the metal disc to either pop up or pop down, thus creating a vacuum within the rubber membrane, or releasing it.
The resulting prototype device is light, inexpensive to build, operates noiselessly, uses relatively little electricity, and can lift and hold objects weighing several kilograms – the technology is scalable, though, so heavier objects could be lifted by including more wires.
Additionally, by monitoring the electrical resistance of the wires and deducing the extent of their deformation from that, it's possible for a control unit to determine if a vacuum is being maintained, so it can issue warnings if it senses that an object isn't being held securely.
The university is currently looking for industrial partners to help develop the technology commercially.
Source: Saarland University
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