Dual-channel sensor measures biomarker concentration in sweat

Sensors applied to the skin hold promise for a non-invasive, low-cost method of identifying key biomarkers in sweat, which could help clinicians make earlier and more accurate diagnoses. Until now, however, sensors could identify the presence of biomarkers, but were not able to accurately detect their concentration in the presence of irregular, intermittent, and unpredictable sweat production.

To address this problem, a team of Penn State researchers developed a sensor that accurately detects biomarker concentrations in sweat samples. Their work was published in Advanced science.

While researchers had already created a sensor that could detect amounts of glucose and other biomarkers, the sensors did not have a way to accurately detect the volume of sweat, meaning the concentration of the biomarkers was unknown. .

“A particular challenge is quantifying this biomarker and sweat rate accurately, because different conditions that cause us to sweat (exercise, hot weather, eating spicy foods) can all have different sweat rates that can be more constant or more constant sweat from time to time,” said Huanyu “Larry” Cheng, James L. Henderson, Jr. Memorial Associate Professor of Engineering Sciences and Mechanics at Penn State.

“This makes it difficult to measure sweat volume, which we need to know if we want to quantify the concentration of the biomarker.”

To evaluate this information, the researchers designed a sensor with two channels to capture sweat: one that will measure the amount of biomarker and one that will measure the volume of sweat. The sensor relies on a dye to signal the presence of the biomarker and can be read with the naked eye, making it inexpensive and easy to use.

According to Cheng, because the sensor results can be read so easily without expensive processing equipment, they could be particularly useful to providers in remote areas.

“The liquid will react with the dye deposited in the channel, changing color, and based on the advancing front of the liquid, we can quantify the rate and volume of sweat based on the line in that channel,” Cheng said. “We use the marks printed near the channel to indicate the volume of sweat to compare, then use the other set of marks to read the concentration at the preset volumes.”

The concentration of the biomarker, not just its presence, is useful for diagnosis. For example, the researchers said their sensor could be used to test for cystic fibrosis, which is often indicated by high chloride levels in the patient.

“The typical procedure to diagnose cystic fibrosis is to induce local sweating through exercise, but with our sensor we can detect the concentration of chloride in sweat without requiring the patient to exercise, since we can use passive heat-induced sweating with our wearable form of the test setup,” Cheng said.

This method, combined with the sensor’s soft materials, makes it better than traditional diagnostic tests for infants and young children, according to Cheng. To test the sensor, Cheng is partnering with doctors at Milton S. Hershey Medical Center for a trial of the sensor.