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Po-Chun Hsu: Engineering Nanostructured Materials to Keep You Cool

New faculty member Po-Chun Hsu designs materials at the nanoscale tailored to transmit, block and absorb thermal radiation

By Ken Kingery

Po-Chun Hsu will join the faculty in the Department of Mechanical Engineering and Materials Science at Duke University’s Pratt School of Engineering beginning January 1, 2019. Part of a string of recent hires focusing on wearable technology, Hsu develops nanofabricated materials with tailored heat transmission properties for applications ranging from walking down the street to walking on Mars.

Hsu has spent the past two years as a postdoctoral researcher at Stanford University—where he also earned his doctorate in materials science and engineering—working on these novel materials. By controlling their structure at the nanoscale, Hsu can dictate how they interact with infrared electromagnetic radiation…or in other words, heat.

This idea is perhaps best illuminated through the title of his research project for the past few years, “Wearable radiative heating/cooling textiles.” Working with his PhD advisor Professor Yi Cui, Hsu developed a nanoporous polyethylene fiber that is breathable and scatters visible light, but is completely transparent to thermal radiation. He also extended this research toward active refrigeration for even faster cooling demand for applications such as buildings and batteries, working with his postdoc advisor Professor Arun Majumdar.

“If a shirt were made of this material, it’d be like wearing any other normal white t-shirt, except that there would be no barrier to the transmission of heat,” explained Hsu. “Whereas cotton absorbs some heat and reemits it back to the body, this material lets heat pass through fully and completely.”

This technology can be translated to many more applications than the coolest t-shirt in history. By sandwiching layers with different nanostructures together, Hsu could make a jacket that lets heat through in one direction but not the other. That is, a jacket that keeps you cool unless you turn it inside out, at which point it keeps you warm instead.

Taking this research a step further, these materials could be tailored to keep out different types of radiation besides just heat. With the right combination of layers, Hsu envisions a lightweight spacesuit that can keep an astronaut safe from radiation while also perfectly regulating their temperature on the surface of Mars. Outside of clothing, these ideas could also be applied to materials meant to keep satellite components safe and warm, or to energy-harvesting devices that need to absorb light or heat.

It may sound futuristic, but the simplest implementation of these materials is already being pursued by a Stanford startup company. As they work to scale up the manufacturing process, Hsu is looking to push the boundaries of what these textiles are capable of.

“I’d love to eventually combine an actively controllable form of this technology with current wearable electronics,” said Hsu. “Imagine if your smart watch could detect the presence of sweat and then send a signal to your clothing to help cool you off. That’s the sort of functionality I want to achieve.”

Hsu is betting that the interdisciplinary nature of Duke University will help get him there. With faculty experts in the realms of heat transfer, polymer physics and biomedical applications, there are plenty of opportunities for collaboration.

It’s the potential practical impacts on daily life that excites Hsu about his research. And with curious students at Duke willing to help him push the limits of the technology, he believes we could all be wearing radiative heating and cooling textiles within the next decade.

“Duke is a special place with a wide variety of talented people,” said Hsu. “It’s the perfect environment to find inspiration for this kind of interdisciplinary research.”