Tiny photonic chip could fit comfortably on your fingertip – sciencedaily
As new infectious diseases emerge and spread, one of the best ways to fight new pathogens is to find new drugs or vaccines. But before drugs can be used as potential remedies, they must be carefully selected for composition, safety, and purity, among other things. Thus, there is a growing demand for technologies capable of characterizing chemical compounds rapidly and in real time.
To address this unmet need, researchers at Texas A&M University have now invented a new technology that can dramatically reduce the size of the device used for Raman spectroscopy, a well-known technique that uses light to identify molecular composition. compounds.
“Raman benchtop configurations can be up to one meter long depending on the level of spectroscopic resolution required,” said Dr. Pao-Tai Lin, assistant professor in the Department of Electrical and Computer Engineering and the Department of Science and Engineering. materials. “We have designed a system that can potentially replace those bulky countertops with a tiny photonic chip that can fit snugly at the tip of a finger.”
In addition, Lin said their innovative photonics device is also capable of performing high-throughput real-time chemical characterization and, despite its size, is at least 10 times more sensitive than conventional bench-top Raman spectroscopy systems.
A description of their study is in the May issue of the journal Analytical Chemistry.
The basis of Raman spectroscopy is the scattering of light by molecules. When struck by light of a certain frequency, molecules dance, spinning and vibrating, absorbing energy from the incident beam. When they lose their excess energy, molecules emit a lower energy light, characteristic of their shape and size. This scattered light, known as Raman spectra, contains the fingerprints of molecules in a sample.
Typical benches for Raman spectroscopy contain an assortment of optical instruments, including lenses and arrays, for manipulating light. These “free space” optical components take up a lot of space and provide a barrier for many applications where chemical detection is required in tiny spaces or hard to reach locations. Additionally, bench tops can be prohibitive for real-time chemical characterization.
As an alternative to traditional bench-top laboratory systems, Lin and his team have turned to tube-shaped conduits, called waveguides, which can carry light with very little energy loss. While many materials can be used to make ultra-fine waveguides, the researchers chose a material called aluminum nitride because it produces a weak Raman background signal and is less likely to interfere with the Raman signal coming from it. ‘a test sample of interest.
To create the optical waveguide, the researchers used a technique used by industry to draw circuit patterns on silicon wafers. First, using ultraviolet light, they spun a light-sensitive material, called NR9, onto a silica surface. Then, using ionized gas molecules, they bombarded and coated aluminum nitride along the pattern formed by NR9. Finally, they washed the assembly with acetone, leaving behind an aluminum waveguide a few tens of microns in diameter.
To test the optical waveguide as a Raman sensor, the research team carried a laser beam through the aluminum nitride waveguide and illuminated a test sample containing a mixture of organic molecules. By examining the scattered light, the researchers found that they could discern each type of molecule in the sample based on Raman spectra and with at least 10 times the sensitivity of traditional Raman benchtops.
Lin noted that since their optical waveguides are very narrow in width, many of them can be loaded onto a single photonic chip. This architecture, he said, is very conducive to the high-throughput real-time chemical detection required for drug development.
“Our optical waveguide design provides a new platform to monitor the chemical composition of compounds quickly, reliably and continuously. In addition, these waveguides can be easily fabricated on an industrial scale by taking advantage of already existing techniques to fabricate semiconductor devices, ”said Lin. “This technology, in our view, has a direct benefit not only for the pharmaceutical industries, but even for other industries, such as petroleum, where our sensors can be placed along underground pipes to monitor the composition of the hydrocarbons.”
Other contributors to this research are Megan Makela of the Department of Materials Science and Engineering; and Paul Gordon, Dandan Tu, Cyril Soliman, Dr Gerard Coté and Dr Kristen Maitland from the Department of Biomedical Engineering.