College of Engineering, Computing and Applied Sciences

New research could open the door to quick, simple diagnostic tests


Judson Ryckman pointed a hand-held laser at a sensor chip in his Clemson University lab. The reflection it made on a white piece of paper taped to the wall looked like a red full moon with green craters.

Ryckman, an assistant professor of electrical and computer engineering, had the lights off and the laser shining to help demonstrate his newest research project. His eyes weren’t on outer space but the unique color changes he and his team can make possible with nano-manufactured sensor chips and the right type of laser light.

The research that Ryckman does is helping raise hopes it could eventually be possible to run a wide range of diagnostic tests without needing large, expensive scientific instruments. Instead of sending samples to a lab, tests would be run at home or in the field and evaluated with the naked eye or a digital camera, Ryckman said.

Judson Ryckman

The potential applications are many, ranging from medical diagnostics to measuring environmental toxins, Ryckman said.

Ryckman recently learned he is receiving a $500,000 CAREER award from the National Science Foundation, enough to fund his project for five years.

“People have been trying to miniaturize lab-on-chip technology for many years, and there’s some very good progress in that area,” Ryckman said. “We’re contributing to that. We’re also trying to take advantage of what is one of the most powerful diagnostic tools we have, which is the human eye.”

Hai Xiao, chair of the Holcombe Department of Electrical and Computer Engineering, said Ryckman’s CAREER award is very much deserved.

“CAREER awards support junior faculty members who model the role of outstanding teacher-scholar,” Xiao said. “This award is a testament to Dr. Ryckman’s outstanding research, excellence in the classroom and his integration of research and education.”

A big challenge in creating tests for at-home and mobile use is finding a way for whatever you are trying to detect to cause a color change dramatic enough that it can be seen by the naked eye or smartphone camera.

That’s the focus of Ryckman’s work.

He and his team make sensor chips with highly specific color-filtering surfaces, and then they shine a laser on them.

“When you introduce the analyte you want to detect, it will shift the properties of that color filter and give a very strong color response that you can see with the eye or with a smartphone,” Ryckman said.

The moon-resembling reflection in his lab, for example, was created with porous silicon, represented by the red area. Researchers added biomolecules that infiltrated the pores and changed the optical properties ever so slightly, making those areas green, Ryckman said.

Part of the research has also focused on figuring out what type of light to use. Ryckman and his team found that a multichromatic laser with red, green and blue wavelengths works better than broadband white light or a monochromatic laser.

Ryckman and a group of researchers reported some of their early findings in a paper published in the December 2020 issue of the Proceedings of the National Academy of Sciences. The article was called “Hyperchromatic structural color for perceptually enhanced sensing by the naked eye.

Tahmid Hassan Talukdar, who was among the co-authors, said COVID-19 highlighted the urgency to develop new sensing techniques.

“With the fast-sensing technique, you are able to detect bacteria and viruses a lot faster than time-consuming techniques,” said Talukdar, who is pursuing a Ph.D. under Ryckman. “In times of pandemic, it comes in handy. If your testing technique is fast enough, you can conduct your test in the morning and get results by evening.”

Also as part of the CAREER award grant, Ryckman plans to establish a new permanent class in silicon photonics and to create a Creative Inquiry course that will give undergraduates a chance to pursue research in the field. The additions are aimed at helping prepare the next-generation workforce with STEM skills.

The CAREER award marks the second time that Ryckman has received an award reserved for top junior faculty members. He received funding in the 2018-19 academic year from the Air Force Office of Scientific Research Young Investigator Program to create smaller and more efficient photonic devices.

Ryckman said the idea for his CAREER award research bloomed from a demonstration that he and his team did in Clemson University’s STEAM Exhibit at Artisphere in downtown Greenville. They introduced the principles of optics to the crowds with colorful laser demos, such as shining red, green, or blue lasers through a light-scattering optical fiber attached to a balloon. (Watch a video of the demonstration here.)

Later, back at the lab, the researchers shined the same laser at some of their sensor chips. Some were very dark with no color change, and some were very vibrant.

“We had to figure out what was happening,” Ryckman said. Eventually, we did figure it out and now we’re optimizing it even further. It’s funny how these things happen– where ideas come from. We’re lucky that we had this light source in the lab, and we were just tinkering around.”

Among those now working on the project is Nithesh Kumar, who is pursuing a master’s degree under Ryckman’s guidance. Kumar said he wants the research to have a positive effect on the world.

“If one day I’m able to help detect something that helps save someone’s life,” he said, “I’m happy with that.”

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