Sweat-Stimulating Biosensor for Continuous Monitoring of Patient Health

A major drawback in the case of medical sensors that analyze human sweat is the factor that it can work only when one sweats.

Sweating by performing excessive physical activity or due to choking ambient conditions in a room may not be feasible for some patients and might be risky for others. And unless they are on the second leg of the Tour de France, patients might probably not want to sweat the entire day just for the sake of a sensor reading.

However, Scientists from the University of Cincinnati have formulated an innovative technique for triggering sweat glands on a small, secluded area of skin such that patients can feel comfortable and can perform their everyday chores without the need for spending a long time on a treadmill.

Jason Heikenfeld, a UC Professor, and Zachary Sonner, a UC Graduate, developed a Band-Aid-sized device including a chemical stimulant that produces sweat even if the person is comfortable and relaxed. The sensors can also estimate the amount of sweat produced by the patients, which is a significant characteristic in having knowledge of the chemicals or hormones measured by the biosensors. The research was reported in Lab on a Chip, a nanotechnology journal, on 25^th July 2017.

The challenge is not only coming up with new technological breakthroughs like this, but also bringing all these technology solutions together in a reliable and manufacturable device.

Jason Heikenfeld, Professor, the University of Cincinnati

Heikenfeld was the co-founder of, Eccrine Systems, Inc., a biosensor company that specializes in this field.

As reported by the market-research firm IbisWorld, the value of biomedical sensors in the medical-device industry is nearly 88 billion US dollars. Moreover, it is anticipated that this figure will be increased multiple times in the coming half a decade due to the development of innovative technology and higher competition.

Heikenfeld played an important role in starting the Cincinnati biosensor company in the year 2013 with assistance from UC’s Technology Accelerator program. He is currently Eccrine System’s Chief Science Officer and was recently promoted as UC’s Assistant Vice President for Entrepreneurial Affairs and Technology Commercialization.

According to Heikenfeld, the company’s research programs are gaining international recognition due to its insightful way in which it revolutionizes health diagnosis and monitoring, he said.

“Doctors would love to know if chemical concentrations are increasing or decreasing over time,” stated Heikenfeld, “What was your baseline before you got sick? Then by measuring the change in concentrations, we know even more about how sick you are or how quickly you are getting better.”

Blood analysis is regarded as the benchmark for biometric analysis. However, performing biometric analysis of blood is invasive and usually necessitates a lab facility. Furthermore, continuous monitoring of blood for many hours or many days is highly tasking for Doctors.

Heikenfeld noted that sweat is a noninvasive substitute, as against tears or saliva, including chemical markers that are highly convenient in observing health.

People for a long time ignored sweat because, although it can be a higher-quality fluid for biomarkers, you can’t rely on having access to it. Our goal was to achieve methods to stimulate sweat whenever needed—or for days.

Jason Heikenfeld, Professor, the University of Cincinnati

Heikenfeld, who is also Director of UC’s Novel Devices Laboratory, has been investigating the challenge for nearly 7 years. Researchers consider that sweat produces nearly the same helpful information related patients similar to blood. He further noted that the challenge has been always gaining the same steady sample as provided by standard blood draw.

“We believe that the solutes you find in blood you will find in sweat,” stated Heikenfeld. “We have postulated that for some time and, as of right now, have not seen anything to change our hypothesis.”

He also explained that analyzing sweat has other prospective advantages over testing blood.

“If you do a blood draw, you get one data point,” he stated. “In many cases, Doctors would love to know if concentrations are increasing or decreasing over time.”

For this research, the Scientists applied a gel containing carbachol (which is a chemical found in eyedrops) and sensors to the forearm of the patient for 2.5 minutes.

The Researchers employed three techniques to acquire data from the sensors: only the sensors and the gel alone, and along with memory foam padding to ensure better contact between the skin and the sensor, and iontophoresis, a 0.2 mA electrical current that makes a small quantity of carbachol to reach the skin’s upper layer and locally stimulates sweat glands without any discomfort or physical sensation.

Subsequently, the Researchers registered data acquired from the sweat of the patient for 30 minutes by using sensors that recorded concentrations of sweat electrolytes. Carbachol proved efficacious in inducing the production of sweat under the sensor for nearly 5 hours. Heikenfeld stated that a successive study fruitfully produced sensor outcomes for many days using this technique for stimulating sweat.

They employed a pH-sensitive orange dye for analyzing the outcomes, where the dye turned blue upon reaction with sweat. This showed that the sweat glands were uniformly stimulated over the area of the sensor.

“This work represents a significant leap forward in sweat-sensing technology,” concluded this research.

Imagine being able to monitor cardiac patients after they have been released from the hospital, or preventing dehydration in athletes or even helping ensure that your body is getting the exact right concentrations of a prescription drug.

Jason Heikenfeld, Professor, the University of Cincinnati

“The ultimate goal is convenience and reliability for biomedical applications,” stated alum Sonner, Lead Author of the paper.

“The end goal is to take the idea from a benchtop test to a portable device—perhaps for people in high-stress jobs like airline pilots—and analyze them for stress,” stated Sonner. “If you’re a pilot, you can’t do blood draws while you’re flying the plane. But a sensor could analyze sweat so we can begin to understand how their body responds to stressful situations.”

The research has been performed at such an instance when many end users are keen on monitoring their own bodily conditions and employing wearable technology to follow their advancement in their wellness or athletic goals.

The sensors designed at UC can assist in tracking alterations in hormones such as cortisol that is liberated when a patient is experiencing stressful conditions.

“Cortisol levels can help trainers know just how hard they need to train an athlete until they are pushing them too far,” stated Sonner.

This is exactly the point at which athletic performance declines and the possibilities of injury drastically increase.

Prospective applications of the sensor surpass Olympic athletes. The U.S. Air Force Research Laboratory at Wright-Patterson Air Force Base, a UC Research Partner, is highly keen on measuring cortisol in pilots under physical and mental stress. According to Heikenfeld, observing their performance and health over a long period of time by employing noninvasive sensors will be exceptionally useful.

Similarly, it can be helpful for subjects who may aspire to monitor their health following a surgery on a regular basis, stated Sonner.

“It’s particularly useful for follow-up visits where normally there is some type of blood testing that has to be done. They could wear a disposable patch for 20 minutes instead,” stated Sonner.

Moreover, saving the money and time needed for going to the Doctor’s office or blood lab is absolutely worth the sweat.