Robotics

Robot hand keeps itself cool by sweating

Robot hand keeps itself cool b...
The fingers on this robot hand sweat to cool down
The fingers on this robot hand sweat to cool down
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When the temperature rises above 30° C, water is squeezed out to evaporate on the surface and cool the finger-like actuator
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When the temperature rises above 30° C, water is squeezed out to evaporate on the surface and cool the finger-like actuator
The fingers on this robot hand sweat to cool down
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The fingers on this robot hand sweat to cool down

As with most electronic gadgetry, getting rid of excess heat from a robot can be the difference between smooth operation and breakdown. Researchers at Cornell University have developed 3D-printed robot fingers that can regulate temperature by sweating.

When we think of robots, plastic and metal beasts like those from Boston Dynamics or even the huge Gundam bot being built in Japan probably come to mind. But not all robots are hard and rigid, some are soft and pliable. And some are a mix of both. Either way, temperature control is an important design consideration.

Metal can be incorporated to help dissipate heat, and fans could be installed in larger builds, but such things are of little use to robots made primarily of soft synthetic materials. Rob Shepherd and his research team looked to mammals like us for a cooling solution.

"The ability to perspire is one of the most remarkable features of humans," said co-lead author on the new research, T J Wallin, M.S. Ph.D. "Sweating takes advantage of evaporated water loss to rapidly dissipate heat and can cool below the ambient environmental temperature. So as is often the case, biology provided an excellent guide for us as engineers."

When the temperature rises above 30° C, water is squeezed out to evaporate on the surface and cool the finger-like actuator
When the temperature rises above 30° C, water is squeezed out to evaporate on the surface and cool the finger-like actuator

The researchers fabricated soft robotic actuators from two hydrogels using a 3D-printing process that uses light to cure resin. The base layer of poly-N-isopropylacrylamide shrinks when temperatures above 30° C (86° F) are encountered, which acts to squeeze water up to a polyacrylamide top layer that's dotted with micron-sized pores.

The pores are similarly temperature-sensitive, and force out the water – or robot sweat – for evaporation on the surface of the fingerlike actuator, which is reported to reduce surface temperature by 21° C within 30 seconds. When a fan blows air toward the actuators, cooling efficiency increases. And the pores close when the temperature drops below 30° C, so regulating overall temperature.

The soft robot fingers were installed as a gripper on a robot hand and used to grab objects, and it was found that the cooling effect also reduced the temperature of the object being handled.

"The best part of this synthetic strategy is that the thermal regulatory performance is based in the material itself," Wallin commented. "We did not need to have sensors or other components to control the sweating rate. When the local temperature rose above the transition, the pores would simply open and close on their own."

There are a few downsides to this approach though. Sweaty fingers might let objects slip and tumble – though changing the texture of the upper layer could help in that regard, essentially giving the skin some wrinkles. The range of mobility could also be compromised. And the robot hand as currently designed needs a regular supply of water to replace what's been evaporated away, though Shepherd sees future robots being able to take in – or drink – water on their own, and perhaps even absorb stuff through their skin. Or maybe future bots could absorb moisture from the air, and store it away until needed – in a similar way to the coated sheets developed by scientists from China's Shanghai Jiao Tong University.

The research has been published in the journal Science Robotics.

Source: Cornell University

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