Sweat sensors that monitor biomarkers could be the secret sauce that differentiates fitness wearables. We’ve written about sweat-sensing technology often, including stretchable sweat sensors developed by scientists at the University of Glasgow School of Engineering. A University of Missouri team discovered that rising sweat levels correlate with aggressiveness with autistic adolescents. Work at UC Berkeley developed a wearable patch with a fluidic channel that wicks up sweat and has sensors to detect various chemicals. Also, a University of Cincinnati College of Engineering and Applied Science group invented a continuous-testing sweat sample device the size of a Band-Aid that measures specific drugs and hormones. These are just a few examples of the wide-ranging work with sweat sensors.

In the latest sweat-sensing technology development, a team of National University of Singapore (NUS) researchers fabricated a flexible, highly-responsive pH sweat sensor that can be incorporated in other wearables with existing pulse oximeters. The NUS team built a prototype pH Watch that uses the sweat sensor as an application example but said the sensor also is suitable for use with armbands, chest straps, or headbands. The sensor, made from inexpensive polyaniline polymer, is durable and flexible. The sensor doesn’t require a power source and lasts a year or longer, even with heavy use. The sensor changes color on contact with sweat and an algorithm that interprets color changes reports the sweat pH with approximately 90% accuracy. Exact specifications are not public, but the thin sensor appears to be approximately 0.5-inches square.

The next steps for the NUS researchers include studying additional sweat biomarkers and seeking further applications of their technology with additional existing sensors.