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Engineers develop micro-tentacle limbs for tiny robots

23 June 2015

A tiny tube circles an ant’s thorax, gently trapping the insect and demonstrating the utility of a micro-robotic tentacle developed by Iowa State University engineers.

A micro-tentacle spirals gently around an ant's thorax (photo courtesy of Jaeyoun Kim/Iowa State University)

“Most robots use two fingers and to pick things up they have to squeeze,” says Jaeyoun  Kim, an Iowa State University associate professor. “But these tentacles wrap around very gently.” And that makes them perfect hands and fingers for small robots designed to safely handle delicate objects.

In a paper published in the journal, Scientific Reports, the engineers describe how they fabricated micro-tubes just 8mm long and less than 0.25mm in diameter from PDMS, a transparent elastomer that can be a liquid or a soft, rubbery solid. Kim has worked with the material for about a decade and has patented a process for making thin wires from it.

One end of the tube is sealed and air is pumped in and out. The air pressure and the micro-tube’s asymmetrical wall thickness creates a circular bend. However, by adding a small lump of PDMS to the base of the tube, this bending motion is amplified to create the desired two-turn spiralling, coiling action.

Spiralling tentacles are widely utilised in nature for grabbing and squeezing objects and there have been continuous soft-robotic efforts to mimic them. However, life-like, multi-turn spiralling motion has been reproduced only by centimetre-scale tentacles so far. At millimetre and sub-millimetre scales, they could bend only up to a single turn.

The Iowa State University micro-robotic tentacle is described as 'S-cubed' (soft, safe and small). Kim believes this makes it ideal for medical applications because it cannot damage tissues or blood vessels.

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