Sweating, often considered unpleasant, plays a crucial role in protecting the body from heat-related risks, particularly in places like Maricopa County, Arizona, which recorded 608 heat-related deaths in 2024. While products are widely marketed to reduce sweating, research into how sweat helps regulate body temperature has been limited.
Konrad Rykaczewski, an associate professor of mechanical and aerospace engineering at the Ira A. Fulton Schools of Engineering at Arizona State University (ASU), has advanced this field by using a unique outdoor thermal manikin named ANDI to study human cooling processes. His recent work, published in the Journal of the Royal Society Interface, focuses on sweat evaporation—the least studied aspect of sweating.
“We know a lot about how the body generates sweat, but when it comes to its evaporation, which is the most important part, we know surprisingly little,” said Rykaczewski.
Rykaczewski’s research demonstrates that even small amounts of sweat evaporating from the skin can remove significant heat from the body. The team used specialized equipment such as mid-wave infrared cameras and optical coherence tomography microscopes to observe how sweat exits pores and spreads across skin for the first time.
“The mid-wave infrared camera is very sensitive to seeing water, and it gives us a high-resolution image of what’s happening on the surface, while the optical coherence tomography microscope shows us a cross-sectional image of what’s happening on the skin,” he explained.
The experiments involved measuring electrical properties of skin and sweat rate under controlled conditions. One challenge was conducting these tests on people rather than static surfaces. “Anyone can easily put a droplet on a surface in a lab and use a microscope to see how it turns into vapor,” Rykaczewski noted. “When you conduct the experiment on a human being, who breathes, shakes and so on, it gets a lot more complex. That’s why it had never been done before.”
Through repeated trials involving heated suits and detailed analysis of tens of thousands of images, Rykaczewski’s team found that sweat appears irregularly—bubbling up in cycles—and then shifts into different modes until saturation occurs. The key finding was that salt left behind after initial sweating improves subsequent cooling by allowing new sweat to spread more evenly over salty skin.
“We found that the biggest factor that helps the body cool faster is salty skin,” said Rykaczewski.
He further explained: “A million years ago, humans weren’t showering every day. Having salty skin was more natural. It’s not hygienic, but it does optimize the cooling of the body. Now, the interesting question becomes, ‘How could we use that understanding to keep people cool in extreme heat?’”
This insight could lead to better designs for clothing or other solutions aimed at enhancing personal cooling during heat waves—a growing concern for cities like Phoenix where ASU researchers have collaborated with city departments and tech startups on safety technologies such as smart traffic cameras (https://www.phoenix.gov/newsroom/street-transportation/2420).
Rykaczewski also addressed current athletic apparel design: Most clothes focus on pulling moisture away from skin for comfort rather than optimizing evaporation at the surface for better cooling efficiency.
“Humans aren’t just heat exchangers,” he said. “How we feel about things matters. The challenge is finding solutions that keep people safe and feel good enough that they’ll actually use them.”
Looking ahead, Rykaczewski plans to incorporate artificial intelligence into his analysis process due to its labor-intensive nature: “I spent a month analyzing 25,000 images from just one experiment and trying to make sure that what I see is accurate,” he stated.
His ongoing work reflects ASU’s reputation for innovation; according to U.S. News & World Report rankings (https://news.asu.edu/20220911-university-news-asu-no-1-innovation-us-news-world-report-eighth-year?utm_source=twitter&utm_medium=asu&utm_campaign=ASURankings&utm_term=USNWR), ASU has been recognized as America’s top innovative university for eight consecutive years.
With further development using AI tools and continued research into biological mechanisms like sweating responses sensed by nerves in human skin—an area he hopes will yield new answers—Rykaczewski aims for practical applications such as making outdoor activities safer during extreme temperatures.
