Soft, flesh-like robots are better than you at sweating.

It's slightly gross and one of humanity's best evolutionary traits. Robots are catching on.

an underwater robot girl connected with metal cables

Cross "sweating" off the list of jobs that haven't been taken by a machine.

A team of researchers at Cornell University and other institutes have developed soft fluidic actuators that can move, grip and sweat to keep cool. A hand built from these flesh-like constructions was able to cool down three times faster than humans and horses, considered some of the best animals when it comes to breaking a sweat. The paper, "Autonomic perspiration in 3D-printed hydrogel actuators," was published Wednesday in the journal Science Robotics.

"At this point, we've made a sweating, multifunctional hydraulic actuator that's self-cooled, and we believe that is a base building block of a general-purpose, adaptive, enduring robot," Robert Shepherd, associate professor in the department of mechanical and aerospace engineering at Cornell University, said during a conference call discussing the machine.

The bending angles of the hydrogel actuator.

Mishra et al., Sci Robot. 5, eaaz3918

But why would you want a sweaty machine? In many ways, one of the great strengths of robots is they don't need antiperspirant to stay dry on the job.

The main benefit is exactly why it's beneficial for humans to sweat. Sending out liquid helps cool down operations. Current soft robots that lack this functionality can destabilize as the temperature rises. Similar to how sweating helps humans push themselves to the limit in activities like sports, these bots are programmed to perspire so they can operate in high heat conditions.

The actuators are made from hydrogels, which can act as heat reservoirs. The soft actuators were built using multimaterial stereolithography, a 3D printing technique previously used by a team at the University of Michigan.

The fingers of the hand each offer a top layer with micropores and a bottom layer that can channel the water. Below 86 degrees Fahrenheit the pores are shut, but the layers start to expand above that point and release moisture. The system grows even more effective when wind from a fan helps cool things further, around six times faster than non-sweaty machines.

There are some small downsides in its current design. The water makes it more slippery, which could make it harder to grip objects. There's also no way to add more fluid to the machine, but Shepherd has one idea.

"The answer is right in front of me," Shepherd said. "I'm drinking coffee. And I think that in order for our robots, the robots that operate via the autonomous sweating that we created, they have to also be able to drink."

The team is not the first to explore fleshy bots with a slightly unnerving side. A team at the Swiss Institute of Technology, which explored more human-like movements to machines, told Inverse in 2017 that it could form part of a shift toward robots becoming as ubiquitous as smartphones and the like.

Robots could one day grow into a common sight – just remember they may need a towel.

Abstract: In both biological and engineered systems, functioning at peak power output for prolonged periods of time requires thermoregulation. Here, we report a soft hydrogel-based actuator that can maintain stable body temperatures via autonomic perspiration. Using multimaterial stereolithography, we three-dimensionally print finger- like fluidic elastomer actuators having a poly-N-isopropylacrylamide (PNIPAm) body capped with a microporous (~200 micrometers) polyacrylamide (PAAm) dorsal layer. The chemomechanical response of these hydrogel materials is such that, at low temperatures (<30°C), the pores are sufficiently closed to allow for pressurization and actuation, whereas at elevated temperatures (>30°C), the pores dilate to enable localized perspiration in the hydraulic actuator. Such sweating actuators exhibit a 600% enhancement in cooling rate (i.e., 39.1°C minute−1) over similar non-sweating devices. Combining multiple finger actuators into a single device yields soft robotic grippers capable of both mechanically and thermally manipulating various heated objects. The measured thermo- regulatory performance of these sweating actuators (~107 watts kilogram−1) greatly exceeds the evaporative cooling capacity found in the best animal systems (~35 watts kilogram−1) at the cost of a temporary decrease in actuation efficiency.
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