Can a clever microfluidic band-aid stop the cheats?

At the end of a gruelling 5,000-metre Olympics race, the athletes push themselves past the finish line, the winners apparently obvious to all. But, moments later an Olympics official examines the athletes’ intelligent sweat patches and alerts his superiors, someone has taken banned substances. No laboratory testing needed, the announcement is made, the athlete that came second is banned, no silver medal for them. Patches, like band-aids, that detect substances in sweat could soon be used by many sports worldwide to ensure clean competitions.

The technology of a band-aid like patch with tiny channels etched in a silicon substrate that can detect chemicals is called microfluidics. Detecting banned substances in athletes’ sweat is one, “possibility, I would say it’s well within the scope of the things we can build,” said John Rogers, a biomedical engineering and materials science professor at Northwestern University. It is possible because blood chemistry is reflected in what can be found in sweat. In the microfluidic sweat sensor device, the sweat travels through the etched channels into compartments where it reacts with chemical reagents. These reactions can produce corresponding colour-change indicators on the devices’ external surface.

Previously used only in laboratories for biology and chemistry applications to help develop medicines, microfluidic device technology is becoming more durable for the commercial world. One of the uses is DNA analysis outside the laboratory. The more durable devices can potentially be deployed at crime scenes. The advantages for forensic DNA microfluidic detection are reduced risks of contamination and shorter analysis time. Another law enforcement application is the detection of alcohol levels and drugs.

Hospitals can also use a patch to help stroke patients. Just as stroke patients will suffer some level of paralysis of one side of their body, their sweat production also diminishes on that affected side. Microfluidic sweat analytics can analyse this sweat to help determine the extent of the stroke’s effect and indicators of improvement during treatment. Another medical use is the detection of creatinine levels. Creatine is a substance linked to kidney health and can help diagnose kidney problems. The devices can also detect glucose, lactate, lead, and arsenic for other clinical purposes.

Rogers’ devices are being used for an improved test for cystic fibrosis in children. He also expects uses for nutrition, skin health and cosmetics. He adds: “You can add electronics to readout [the result] on top of it [the patch] and that is an option we’re looking at in the future.” Wearable microfluidic devices can also be used with mobile phones. A mobile’s app can examine a phone camera photo of a patch and interpret the colours for a more accurate diagnosis.

Rogers is a founder of the microfluidic sensor company Epicore Biosystems and its first products are in testing with a variety of partner organisations such as beverage maker Gatorade and the Seattle Mariners baseball team. Beverage makers, such as Gatorade, are interested in using sweat data to provide personalised drinks designed to help an individual’s hydration. The Seattle Mariners are using it to help player performance. The Epicore devices can also be used for aquatic sports, even underwater. Northwestern university’s swimming team now routinely use Epicore’s device.

From swimmers to runners to baseball players, whether it is performance monitoring or an anti-doping measure, the clever microfluidic band-aid could be an answer to many of sports’ ills while also helping sufferers of other illnesses improve their quality of life.

Biomedical sensing has moved on a long way since we published: "Is this the World’s most energy efficient biomedical sensor hub?" back in 2016.