A recent Medgadget article discussed an innovative new method for collecting sweat for biomedical analysis that was inspired by an unlikely source: cacti. Apparently a team of researchers at South Korea’s Pohang University of Science and Technology examined the way the spines of cacti draw tiny amounts of water from their tip to their base and applied it to a tiny patch. This is doable thanks to a unique phenomenon known as Laplace pressure, where a pressure differential between the inside and outside of a water droplet mobilizes it along the spine.
The researchers created a patch that contains tiny wedge-shaped patterns. Some areas are hydrophobic, and some are hydrophilic, which causes pressure differentials along the patch’s surface that act as funnels that passively pull sweat away from the skin and into the patch. The method collects sweat quicker than traditional microfluidic channels to enable continuous sweat monitoring, which could revolutionize the potential of sweat analysis technology.