A team of researchers from Pohang University of Science and Technology in South Korea created a passive sweat collection device that is inspired by cactus thorns. The device is intended as a means of collecting sweat for biomedical analysis; for example, to measure glucose levels in patients with diabetes. Having the ability to operate without a power source, the patch can passively collect small amounts of sweat efficiently, helping to unlock the potential of sweat analysis technology.
Sweat analysis is very promising as a way to diagnose and control a variety of diseases. The basic idea is that a patch worn on the skin will collect sweat non-invasively and then analyze it. The technique has many advantages in terms of non-invasive sampling and continuous monitoring, but so far it has failed to take off as a viable alternative to sampling other body fluids, such as blood or urine.
Part of the problem is getting enough sweat to analyze it without first asking someone to do activities, such as exercise, that induce heavy sweating. This is hardly convenient, so devices that can maximize the amount of sweat they collect can help the technology move toward a discreet laptop that can control the disease without any hassle.
To increase the efficiency of sweat collection from a patch to carry, Korean researchers turned to nature to look for ideas. They were inspired by the thorns of cacti, which attract small amounts of water from the tip to the base by a process called Laplace pressure, where a pressure differential between the inside and outside of the drops of water causes them to move along the spine.
This process is very efficient in collecting small amounts of water, allowing the cacti to survive in desert conditions. To exploit the same phenomenon, the researchers created wedge-shaped patterns within the patch, with hydrophobic zones and hydrophilic zones. Patterns maximize the pressure differential between the front and back of a sweat drop and act to channel sweat away from the skin and into a patch that can be worn.
To date, researchers have reported that the technology can collect sweat faster than conventional microfluidic channels, which could allow for continuous monitoring of sweat. “Difficulties in collecting sweat have made it difficult to use on portable sanitary devices,” said Professor Kilwon Cho, one of the leaders in patch development. “This newly developed patch solves this problem by quickly collecting sweat and making it easier to use on a variety of portable sanitary devices, including blood sugar control.”
Study a Advanced materials: Sweat collection patch inspired by the cactus spine for fast and continuous sweat monitoring