Biomarkers, Sweat and Tears

An eight-hour fast, a pin prick, and a blood test. Standard procedure when testing for diabetes, but could the same diagnosis be made by wearing an epidermal patch instead? Researchers at Northwestern University are working towards making that a reality with their “lab on the skin” device which collects, stores, and analyzes sweat in real time (1). Why focus on sweat? John Rogers, Professor of Materials Science and Engineering at Northwestern University, explains, “Sweat is an interesting class of biofluidics because it can be captured noninvasively. We were looking to work on a simple type of device capable of performing in situ chemical analysis of sweat, as well as analyzing sweat rates and total sweat loss.” Importantly, sweat contains an array of biomarkers that can be vital indicators of health and physiological status. Could this approach present a feasible solution to invasive sampling and, importantly, a viable diagnostic option? That’s certainly the hope.

This is how. The wearable epidermal device collects sweat through microchannels and displays pH, chloride, glucose, and lactate levels via colorimetric analysis. An embedded NFC coil allows the wearer to optionally connect their phone to the device with a simple tap, then take a photo of the device, enabling the phone to quantitively determine the status of each metric. 

The investigators have previously developed a suite of electronic devices that interface with skin in order to perform clinical quality measurements. This latest device is an evolution of those projects – cheap, durable, and power-free, but focused more on fluids and chemicals than on electronics. Their current aim is for the microfluidic device to be used in fitness settings, but clinical applications are on the way. Rogers explains, “We’re focused first on fitness and sport, partly because the application requirements are relatively easy to meet. But we’re simultaneously exploring sweat glucose measurements with relation to diabetes patients, and sweat chloride measurements as an assessment of cystic fibrosis.” The team have also suggested that the device could be modified to noninvasively test other bodily fluids, such as tears or saliva.

As for the future of the device, the plan is to continue refining it for clinical use in diabetes and cystic fibrosis, as well as improving its mechanics. “In terms of technology, we’re taking the next steps in integrating fluidics with electronic/optoelectronic functions beyond what we’ve demonstrated with our ‘lab on the skin’ device,” concludes Rogers.