Research collaboration between RIT and Cornell produces new technique to enhance sensors and photonic devices

Researchers have discovered new ways to bend light to improve optical applications such as sensors, displays, and next-generation photonic devices.

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RIT/University Photography

Steve Weinstein, professor of chemical engineering, Kate Gleason College of Engineering.

Steve Weinstein, professor of chemical engineering at Rochester Institute of Technology, co-authored a paper with Cornell University faculty-researcher Richard Robinson about a robust, scalable method to generate chiral films for advancing photonic technologies. The article was published Jan. 30 in Science magazine.

Chirality is the property where objects exist in left-handed or right-handed forms, like mirror images, except that they cannot be superimposed. Chiroptics focuses on how these chiral structures interact with light, often twisting its polarization. The new research details the advantages of those optical techniques for advancing semiconductor technologies, Weinstein explained.

“Introducing chiral properties into semiconductors is desirable because it permits simultaneous control over light, spin, and charge—key capabilities for advancing next-generation photonic and optoelectronic applications,” said Weinstein. The new work details fiber self-assembly in an evaporative deposition process. Weinstein developed a theoretical framework to interpret observed fiber deposition patterns, why they twist, and how the twist is affected by fluid flow during evaporation and formation of the fibers in solutions.

Chiral nanomaterials could offer a groundbreaking approach to non-invasive glucose monitoring, for example, by controlling the unique way glucose rotates polarized light. By integrating these chiral materials into sensors to amplify light signals, subtle changes can be revealed in polarization, enabling highly sensitive glucose detection through the skin. This technology would eliminate the need for painful finger pricks, paving the way for continuous and more comfortable glucose tracking.

Chirality is common in molecules found in living organisms such as DNA and in inorganic systems, like snail shells. One way to produce a chiroptical response is to assemble small nano-sized units together into a helical, or spiral, assembly.

In the inorganic world, semiconductors have not yet been made into these chiral, exciton-coupled assemblies. Weinstein and Robinson were able to refine a directional drying process technique to form helical semiconductor nanoclusters that have a chiral optical response.

“This is the first report of its kind that we know of, and the processing is based on the simple mechanism responsible for the common coffee ring that is observed as a droplet dries,” said Weinstein. “Our investigation examines the large-area films that are formed and the mechanisms behind them. The result is the highest chiral signal reported for inorganic materials to date. This evaporation-driven technique not only induces nanometer-scale fiber twists but also allows us to tune their chiroptical properties by controlling the flow parameters.”

Robinson, lead author on the article and principal investigator of the National Science Foundation grant for this work, said that future aspects of the project will focus on extending the technique to other materials such as nanoplatelets in quantum dots.

Weinstein originated the mechanistic origin of the phenomena discussed in the paper—and the team from both RIT and Cornell will continue the work with funding from the Department of Energy to examine that mechanism in more detail and to perform relatively sophisticated mathematical modeling of the proposed mechanism. Along with his position in RIT’s Kate Gleason College of Engineering, Weinstein has been a research adjunct at Cornell University for more than 20 years. He collaborated on projects with Cornell’s materials science and chemical engineering researchers and students.