Light-analyzing lab-on-a-chip opens the door to widespread use of portable spectrometers

Scientists, including an Oregon State University materials researcher, have developed a better tool for measuring light and contributed to a field known as optical spectrometry that could improve everything from smartphone cameras to environmental monitoring.

The study published today in Sciencewas led by Finland’s Aalto University and resulted in a powerful, ultra-small spectrometer that fits on a microchip and is powered by artificial intelligence.

The research involved a comparatively new class of super-thin materials known as two-dimensional semiconductors, and the result is a proof of concept for a spectrometer that could easily be integrated into a variety of technologies – including quality inspection platforms, security sensors and biomedical analyzers and space telescopes.

“We have demonstrated a way to build spectrometers that are much smaller than those commonly used today,” said Ethan Minot, professor of physics at the OSU College of Science. “Spectrometers measure light intensity at different wavelengths and are extremely useful in many industries and all areas of science to identify samples and characterize materials.”

Traditional spectrometers require bulky optical and mechanical components, while the new device could fit on the tip of a human hair, Minot said. The new research suggests these components can be replaced with novel semiconductor materials and AI, allowing spectrometers to be dramatically downsized from the current smallest, which are about the size of a grape.

“Our spectrometer does not require the assembly of separate optical and mechanical components or array designs to diffuse and filter light,” said Hoon Hahn Yoon, who led the study along with Zhipei Sun Yoon, a colleague from Aalto University. “In addition, it can achieve high resolution comparable to benchtop systems, but in a much smaller package.”

The device is 100% electrically controllable in terms of the colors of light it absorbs, giving it huge potential for scalability and broad applicability, say the researchers.

“Direct integration into wearable devices such as smartphones and drones could advance our daily lives,” Yoon said. “Imagine if the next generation of our smartphone cameras could be hyperspectral cameras.”

In addition to capturing and analyzing information from visible wavelengths, these hyperspectral cameras could also enable infrared imaging and analysis.

“It’s exciting that our spectrometer opens up possibilities for all sorts of new everyday devices and instruments to also do new science,” said Minot.

In medicine, for example, spectrometers are already being tested for their ability to detect subtle changes in human tissue, such as the difference between tumors and healthy tissue.

For environmental monitoring, Minot added, spectrometers can tell exactly what type of pollution is in the air, water or soil, and how much of it is there.

“It would be nice to have inexpensive, handheld spectrometers that do this work for us,” he said. “And in education, practical teaching of scientific concepts would be more effective with inexpensive, compact spectrometers.”

Applications also abound for science-minded hobbyists, Minot said.

“If you’re interested in astronomy, you might be interested in measuring the spectrum of light you collect with your telescope and being able to use that information to identify a star or planet,” he said. “If geology is your hobby, you could identify gems by measuring the spectrum of light they absorb.”

Minot believes that as work on two-dimensional semiconductors continues, we will “quickly discover new ways to exploit their novel optical and electronic properties.” Research into 2D semiconductors has only been pursued in earnest for a dozen years, beginning with the study of graphene, carbon arranged in a honeycomb lattice one atom thick.

“It’s really exciting,” said Minot. “I believe we will continue to make interesting breakthroughs as we study two-dimensional semiconductors.”

In addition to Minot, Yoon, and Sun, the collaboration included scholars from Shanghai Jiao Tong University, Zhejiang University, Sichuan University, Yonsei University, and the University of Cambridge, as well as other researchers from Aalto University.