“A drop of sweat” – this phrase is familiar to us, but it’s not entirely accurate. Scientists would more precisely say: “a film of sweat” or “a puddle of sweat.”
A new study from the University of Arizona has revealed that human sweat doesn’t emerge from skin pores as individual droplets, as we often imagine, but rather as nearly flat, shallow puddles.
When a sufficient number of sweat pores fill to the brim, the excess sweat forms a very thin film on the skin’s surface, less than 0.1 millimeters thick.
Using infrared thermography, which allows for the detection of individual sweat pores, a university team led by mechanical engineer Síbín José was able to observe them in astonishing detail.
“Previously, sweating was primarily studied using macroscopic physiological methods, while the dynamics of sweating at micro and macro levels remained unexplored,” the researchers noted.
What Did the Scientists Discover?
During the experiments, six healthy participants lay in reclining chairs, wrapped in electric blankets that kept them warm.
As the temperature changed, sweat appeared on the volunteers’ foreheads and evaporated in a repeating cycle. When the blankets heated the participants’ bodies, their pores gradually filled with sweat until it overflowed, accumulating on the skin and mixing with sweat from other overflowing pores. If droplets of sweat occasionally rolled down their foreheads, it was likely due to gravity.
After the volunteers completed one cycle of sweating and cooling, a layer of salt remained on their skin. During the second heating cycle, this salt facilitated the quicker formation of the sweat film, Science Alert reported.
“When sweat reaches the edge of the pores during the second heating stage, it comes into contact with the surrounding salt deposits, absorbs into them, and spreads, quickly forming a thin film on the skin,” the authors of the study explained in their report. The team hopes that their approach will help understand how the sweating process varies depending on body parts, physical activity, and age groups.
According to the researchers, their study significantly expands the scientific understanding of the fundamentals of human microscale sweating. This knowledge could have wide applications in clinical diagnostics, textile engineering, and the development of wearable sensors.
The results of the study were published in the Journal of The Royal Society Interface.