Novel Microscope Chemically Recognizes Micron-Sized Particles

The Optical Society scientists from the Massachusetts Institute of Technology’s Lincoln laboratory, USA, illustrated their novel microscope by estimating infrared spectra of individual 3-micron spheres made or acrylic or silica. The novel method employs a simple optical setup comprising of compact components that will enable the instrument to be miniaturized into portable equipment about the size of a shoebox.

“The most essential benefit of our novel advantage is its highly sensitive, yet remarkably simple design,” says Ryan Sullenberger, an associate staff at MIT Lincoln Labs and first author of the study. “It offers novel opportunities for non-destructive chemical analysis while paving the method towards ultra-sensitive and more compact instrumentation.”

The ability of the microscope to recognize singular particles could make it useful for rapid detection of chemical threats or regulated substances. Its high sensitivity is also useful for scientific analysis of very minute samples or for estimating the optical properties of substances.

Infrared spectroscopy is typically employed to identify unknown substances as almost every substance can be recognized by its unique infrared absorption spectrum, or fingerprint. The novel technique identifies infrared fingerprint without employing infrared detectors. Such detectors add significant bulk to conventional instruments that is limiting for portable devices as of their requirement for cooling.

The novel method works by illuminating particles with both a green laser and an infrared laser. The infrared laser deposits energy into the particles, making them heat up and expand. The green laser light is then dispersed by such heated particles. A visible wavelength camera is employed to monitor this scattering, and track physical alterations of the individual particles through the lens of microscope.

The instrument can be employed to identify the material composition of separate particles by tuning the infrared laser to distinct wavelengths and gathering the visible scattered light at each wavelength. The slight heating of the particles does not create any permanent modifications to the substance, making the technique useful for non-destructive analysis.The potential to excite particles with infrared light and then consider their scattering with visible wavelengths is a process known as photothermal modulation of Mie scattering that has been employed since the 1980s. Such novel work utilizes more advanced optical components to prepare and identify the Mie scattering and is the very first to use an imaging configuration to identify multiple species of particles.

Conclusion

“We are actually imaging the area that we are interrogating,” says Alexander Stolyarov, technical staff and a co-author of the study. “This implies we can simultaneously analyse numerous particles on the surface at the same time. The one biggest challenge is but the presence of interferon’s that need to be anticipated and combat. Although, contamination is a big problem for any method estimating absorption from tiny volumes of materials, I think our method can solve that problem because of its potential to study one particle at a time.”