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Students may sweat out the results of their math test. They may sweat out an invitation for a date. They may sweat out admission to a graduate program.

Sweat has been on Andrew Sternhagen’s mind a lot lately and it has nothing to do with his prospects concerning a young coed. Sternhagen, an electrical engineering major at South ��ֱ���� State University, is working under the guidance of electrical engineering assistant professor Xiaojun Xian to create a sweat biosensor.

The Brookings native, who just completed his freshman year, is one of 12 selected in December 2024 as a Future Innovators of America.

The program of the Jerome J. Lohr College of Engineering provides recipients with $5,000 with $4,500 as a stipend and $500 to cover the cost of lab supplies or travel to disseminate the results of their project. 

The fellowships were created to provide unique research opportunities for undergraduate students in the college. Any student is eligible to apply as long as they are attending full time and have a GPA of 3.0 or higher. 

Each student works with a potential project mentor, who must be a faculty or research staff member, to develop and submit a research plan that entails learning by doing. 

Exploring biomedical engineering

Sternhagen came to SDSU after excelling in math and biology at Brookings High School. He has an interest in and plans to minor in biomedical engineering. “With the help of Dr. Xian, I’m in this fortunate position,” Sternhagen said of his status as a Future Innovator.

Xian said he recommended Sternhagen as a Future Innovator because of his strong interest in biomedical research and his impressive problem-solving skills. He suggested creating the sweat biosensor because of its potential to enable real-time, noninvasive health monitoring through a compact wearable platform.

Sternhagen explained, “Sweat is a biofluid that is rich in biomarkers and easily obtained. This provides a great opportunity for the creation of noninvasive wearable biosensors. For this research project, we created a microfluidic sweat collection patch using clear flexible silicone polymers with an integrated digital camera chip imager for the continuous collection and analysis of sweat.”

He started working on the project at the beginning of spring semester and plans to be done with this phase before school starts Aug. 25.

Sternhagen’s start pleases Xian

Given that this is Sternhagen’s first experience in a college lab, Xian is pleased with how Sternhagen has done. 

“Since joining my group, Andrew has developed a wide range of research skills, including scanning electron microscopy, sensor fabrication, image processing, data analysis and scientific presentation. Andrew is capable of independently solving many research problems, including designing and fabricating microfluidic channels, and he is highly efficient at multitasking,” Xian said.

Sternhagen said there have been trials along the way, but he is likewise satisfied and hopes to further develop the project in 2025-26. The biosensor includes a camera, a sensor and the patch made of clear silicone polymers.

He said, “The concepts don’t feel too bad, but getting everything to work together as it should” has been the biggest challenge. “When you put everything together, it gets messy. Getting the camera, sensor and patch to all play together is the heart of the difficulty, to make everything play together consistently.” 

Within the patch is a sensing disc and a CMOS (Complementary Metal-Oxide-Semiconductor) chip like found in a phone camera, which records a change in color in the sensing disc. For example, “When the chloride sensor goes from brown to yellow, it indicates you may have cystic fibrosis,” Sternhagen said.

He and Xian also have experimented with sensors for glucose (a diabetes indicator) and lactate (for exercise intolerance), Sternhagen said.

The beauty of such sensors is they are noninvasive. “There is no need to draw blood or have something stick onto your skin like a glucose monitor,” Sternhagen said.

Considered a start-up project

At this stage, Sternhagen’s project isn’t particularly novel. “This project is really getting the foot in the door. With that understanding, we can work into getting that more novel, better sensor,” one in which the camera would not need a lens because it sits right on top of the sensing disc, Sternhagen shared.

“Such a structure could enable a highly compact and multiplexed wearable sweat sensor,” Xian said. However, the challenge lies in developing an innovative method to fabricate microfluidic channels directly on top of the CMOS imager chip.

During the spring semester phase, Sternhagen used a saline solution that imitated human sweat, including pH and sugars. On July 12, Sternhagen did run the Beef and Eggs 5K and collect his sweat for future testing. Other than that, the project is down to data analysis and report writing, which he hopes to present a research conference sometime.

“The goal is to create a process that has a smaller sensor that can give more accurate results,” Sternhagen said of his 2025-26 plans.

Where the project or Sternhagen’s future career will end up is anybody’s else. With three years of undergraduate school remaining, Sternhagen has not locked into a career track.

However, his 10-hour per week “job” working in a basement lab at Daktronics Engineering Hall has given him an understanding of the process for coordinating procedures and learning that most problems are conquered gradually.

That’s applicable to any career.