A research group at Harvard University (Boston/USA) has developed elastomeric grippers that use pneumatic networks. This makes it possible to hold pressure-sensitive objects gently without damaging them.
To incorporate the pneumatic networks into the grippers, the team first used a 3-D printer to make molds from ABS. These were then used to produce castings from a commercially available silicone elastomer, creating layers with open channels. Following this, the researchers sealed off the channels by bonding membranes to the elastomer with the aid of an adhesive.
To create a gripping motion, the channels are pressurized with compressed air. This causes the channels to expand in the directions exhibiting the least resistance. In homogeneous elastomers, expansion occurs at the locations with the thinnest walls; for various materials, these are the regions consisting of the softer material. In response to the expansion of the chambers, the entire gripper curves in on itself.
These elastomeric grippers off numerous benefits over conventional hard gripping elements made from metal. The soft surface of the grippers makes it possible to distribute force uniformly over the entire contact area. The mechanical load on the objects to be moved is minimal, making the grippers ideal for objects with irregularly shaped or pressure-sensitive surfaces. In addition, the grippers are easy to produce. The pneumatic gripping motion does not require a complex controller that uses sensors. In the experiments, it was possible to grip objects with a diameter of 10 cm and a mass of up to 300 g. These values can be increased through use of modified surfaces and elastomers with greater stiffness.
The researchers see potential applications for this technology in surgery, unmanned space flight and remote-controlled disarming of explosives. In experiments with a starfish-shaped gripper, objects as fragile as a raw egg or an anesthetized living mouse were moved without risk of damage or injury.
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