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Dual-wavelength metalens enables Epi-fluorescence detection from single molecules
Summary
Researchers developed an ultra-thin lens device — thinner than a human hair — that can detect and track individual fluorescent molecules and nanoparticles, including those ranging from just a few nanometers to hundreds of nanometers in size. This technology could enable portable, miniaturized sensors for environmental monitoring of nanoscale pollutants like nanoplastics.
Abstract Single molecule fluorescence spectroscopy is at the heart of molecular biophysics research and the most sensitive biosensing assays. The growing demand for precision medicine and environmental monitoring requires the creation of miniaturized and portable sensing platforms. However, the need for highly sophisticated objective lenses has precluded the development of single molecule detection systems for truly portable devices. Here, we propose a dielectric metalens device of submicrometer thickness to excite and collect light from fluorescent molecules instead of an objective lens. The high numerical aperture, high focusing efficiency, and dual-wavelength operation of the metalens enable the implementation of fluorescence correlation spectroscopy with a single Alexa 647 molecule in the focal volume. Moreover, the metalens enables real-time monitoring of individual fluorescent nanoparticle transitions and identification of hydrodynamic diameters ranging from a few to hundreds of nanometers. This advancement in sensitivity extends the application of the metalens technology to ultracompact single-molecule sensors.
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