Can Robots Sweat To Prevent Overheating?
Earlier this year Cornell published a paper on how soft robots can protect themselves from overheating
Robots today are capable of numerous exciting things. From lifting cargo at ports to assembling car parts, from performing precision surgery to delivering pizzas, robots have become an indispensable member of human life. While robots are busy carrying out human activities, did you know robots can sweat too? Earlier this year, researchers at Cornell’s School of Engineering achieved this feat by creating the world’s first soft robotic muscle, so to speak, with the ability to autonomously regulate its internal temperature. According to Rob Shepherd, associate professor of mechanical and aerospace engineering at Cornell, who led the project, this form of thermal management is a basic building block for enabling untethered, high-powered robots to operate for long periods without overheating.
Unlike its metallic counterparts, this robot is 3D printed hydrogel-based composite resins. Each finger’s body was made of a resin that shrunk when heated above 40 degrees C, whereas the back of each finger was capped with a resin that expanded when heated above 30 degrees C. The robot’s pores were made using multi-material tereolithogaphy, a 3D-printing technique that shapes resin by using light. The finger fluidic elastomer actuators’ pores help it to autonomically open and close in response to thermal fluctuation. When the temperature rises, the soft robot manages its internal temperature by dilating micron-sized “pores,” releasing water when its base layer made of poly-N-isopropylacrylamide reaches temperatures above 30 degrees C (86oF). According to measurements by the researchers, subsequent evaporation of this water reduces the surface temperature of the “fingers” by 21 degrees C within 30 seconds. When the temperature drops below 30 degrees C, the pores tighten again, and the perspiration stops. This cooling rate is about three times more efficient than human perspiration.
Further, this mechanism yields a cooling rate of over 600% faster than similar non-sweating devices when used in combination with a fan. Apart from that, the sweat or water’s potential to make the robot’s hand slippery was balanced by upgrades in the hydrogel texture to improve grip, almost akin to building wrinkles into skin.
“The ability to perspire is one of the most remarkable features of humans,” explained T.J. Wallin, co-lead author and a research scientist at Facebook Reality Labs. “Sweating takes advantage of evaporated water loss to dissipate heat rapidly and can cool below the ambient environmental temperature… So as is often the case, biology provided an excellent guide for us as engineers.” Hence, the team’s motivation was to develop an approach to internally cool robot components (hands) using liquids, in contrast to bulky fans with metallic motors.
The researchers at Cornell confirmed the robots‘ gripping ability with a 3-pronged grabber. The hand managed to pick up hot objects, and the material reacted to the high temperature by sweating—no extra sensors or electronics required. This version of the bot didn’t have a way to retain more water, but the researchers say that a future iteration could. Jonathan Rossiter, head of the soft robotics group at Bristol Robotics Laboratory, believes that doing so would provide a natural solution to one of soft robotics’ biggest hurdles. Another primary concern that needs to be worked on in this system is the loss of the robot’s mobility with Sweating. Future versions could separate the water networks behind Sweating and mobility, at the expense of greater complexity, Wallin informed.
The team’s paper, “Autonomic Perspiration in 3D Printed Hydrogel Actuators,” was published on Jan. 29 in the journal Science Robotics. The research was supported in part by the Office of Naval Research Young Investigator Program.