Are you healthy? Check your sweat

Researchers at Northwestern University, Evanston, IL, have developed a skin patch that measures your health by monitoring your sweat. The battery-free microfluidic patch analyzes the chemicals in sweat to provide real-time readings of glucose, pH, lactate, and chloride levels, as well as total sweat loss.

Although the sweat patch is being tested in athletes (a recent Gatorade commercial featured Serena Williams wearing it), it may eventually be used as a glucose monitor for people with diabetes or for sensing other clinical conditions.

“Sweat is an interesting biofluid because it can be collected non-invasively and it has a lot of important biomarkers that relate to health and fitness and physiological status,” said the lead developer of the device, John A. Rogers, PhD, the Louis Simpson and Kimberly Querrey Professor of Materials Science and Engineering, Biomedical Engineering and Neurological Surgery, Northwestern University.

“And our goal was to develop a new device platform that can integrate directly with the skin and capture sweat as it’s released from sweat glands, route it around in very tiny microchannels that are embedded in this very thin, soft material, and perform colorimetric analysis of key biomarkers for the purposes of health and wellness determination,” Dr. Rogers explained.

A monitor with many uses

The first-of-its-kind sensor is a soft, flexible patch that adheres to the skin and is placed directly on the forearm or back. It’s a little larger than a quarter and about the same thickness. Designed for one-time use of a few hours, the simple, low-cost sensor is embedded with colorimetric assays that, when viewed through a smartphone camera, provide an instant wireless readout of physiological status through an app on the phone.

In a recent study published in Science Advances, Dr. Rogers’ team performed a rigorous 2-day field test that compared the sweat patch sensor with blood tests. They found that results from the sweat patch were comparable to those of blood tests, which demonstrated that the sweat sensor has “both the ability for long-term use and the potential for noninvasive tracking of blood analyte concentrations,” the researchers wrote.

Dr. Rogers’ team plans to further optimize the device’s performance and validate it in large-scale clinical trials in humans, including patients with diabetes. They also anticipate adapting the sensor for a variety of other uses, including tracking kidney disease, screening for cystic fibrosis, monitoring pharmacokinetics, and measuring the effects of pressure ischemia and stress markers.

Other biosensors

Although this is the first biosensor of its kind to measure physiologic biomarkers from sweat, several other wireless, wearable biosensors are also currently in development or already on the market:

• Sensor for UV overexposure (developed by Dr. Rogers’ team)
• Contact lens for glaucoma monitoring
• ECG arrhythmia detector
• Smart bandage for monitoring chronic wounds
• Heart rate monitor (also tracks respiratory rate, skin temperature, and physical activity, and detects falls)
• Smart diaper for urinary tract infections in older adults

The market for wearable biosensors is only expected to grow, exceeding more than $31 billion by 2024, according to market analysts.