Tiny grippers capable of grabbing and moving microscale objects have been developed by researchers from Johns Hopkins University.

David Gracias, assistant professor of chemical and biomolecular engineering at Johns Hopkins University, and his team based the tetherless grippers on human hands, which have rigid phalanges and flexible joints. The grippers’ trilayer structure consists of a film made of chromium and copper layer topped with a polymer.

The Johns Hopkins University grippers exploit benign cues such as temperature of biomolecules to trigger gripping and release motions.

Gracias explained: “The film is like a stretched rubber band, when you release it; it immediately tries to curl up.”

The polymer controls whether the film curls up. If the polymer is stiff, the gripper stays open. When the polymer is softened by temperature or chemical triggers, the gripper closes around its target. The grippers release again when another chemical is applied.

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Researchers at the University of Illinois have developed a low-temperature, catalyst-free technique for growing copper nanowires. These copper nanowires could serve as interconnects in electronic device fabrication and as electron emitters in a television-like, very thin flat-panel display known as a field-emission display.

Hyungsoo Choi, a research professor in the Micro and Nanotechnology Laboratory at The University of Illinois, explained: “The copper nanowires are grown on a variety of surfaces, including glass, metal and plastic by chemical vapour deposition from a precursor.

“The patented growth process is compatible with contemporary silicon-processing protocols.”

Typically, the nanowires of 70 to 250 nanometers in diameter are grown on a silicon substrate at temperatures of 200 to 300°C and require no seed or catalyst. The size of the nanowires is controlled by the processing conditions, such as substrate, substrate temperature, deposition time and precursor feeding rate. The columnar, five-sided nanowires terminate in sharp, pentagonal tips that facilitate electron emission.

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