By better understanding the behavior of water in its smallest form, a Virginia Tech professor and his undergraduate student could be improving the efficiency of removing condensation in a major way.
Jonathan Boreyko, an assistant professor in the Department of Biomedical Engineering and Mechanics in the Virginia Tech College of Engineering, has been studying “jumping” dew droplets since he discovered the phenomenon in graduate school.
According to Boreyko, dew droplets jump from water-repellent surfaces only when they reach a large enough size, about 10 micrometers, but it was unclear why until Boreyko and his students made a breakthrough discovery, published in the high-impact journal ACS Nano.
In Boreyko’s lab, then-undergraduate Megan Mulroe, who is first author on the published paper and studied engineering science and mechanics, experimented with the surface of silicon chips to see how the nanoscopic topography of the surface might impact the jumping ability of condensation.
By creating and testing six different types of surfaces covered with so-called nanopillars — reminiscent of stalagmites on a cave floor — Mulroe found that the critical size of the jumping droplet can be fine-tuned based on the height, diameter, and pitch of the nanopillars.
“I didn’t expect a minor alteration to change so much about how condensation behaves on a surface,” Mulroe said. “Only a few hundred nanometers difference in the surface’s topography can stop the phenomenon [of jumping] altogether.”
Essentially, when the nanopillars are tall and slender, the droplets formed inside and on the crevices can jump off the surface at a much smaller size, down to two micrometers. Likewise, short and stout pillars increase the size of the droplet required to jump — up to 20 micrometers in the case of Mulroe’s experiment.
Read the full story via VT News