Researchers have developed a wearable biosensor resembling a bandage that samples sweat and uses a simple color-changing assay to quantify various components. Compared with other biofluids such as blood, sweat has the potential to be obtained less invasively for diagnostic testing. Other tools, such as temporary tattoos or microfluidic devices, have been developed previously but typically require wires, electronics, or sophisticated structures.
To make their device, the researchers coated a flexible polyester film with a super-hydrophobic silica suspension. They then etched microwells into the silica layer to collect perspiration. At the bottom of the wells, they placed dyes that change color with pH or concentration of chloride, glucose or calcium.
The team added an adhesive backing and attached the biosensor bandage onto a volunteer’s skin. When the person exercised, their perspiration collected in the microwells, and the spots changed colors. By imaging and analyzing the colors with a cell phone, the researchers determined that the sweat pH was 6.5–7.0, with a chloride concentration of about 100 mM and trace amounts of calcium and glucose. The researchers are now working on increasing the sensitivity of the device.