Spectrally encoded angular light scattering

Abstract

The angular light scattering profile of microscopic particles significantly depends on their morphological parameters, such as size and shape. This dependency is widely used in state-of-the-art flow cytometry methods for particle classification. We introduce a new spectrally encoded angular light scattering method, with potential application in scanning flow cytometry. We show that a one-to-one wavelength-to-angle mapping enables the measurement of the angular dependence of scattered light from microscopic particles over a wide dynamic range. Improvement in dynamic range is obtained by equalizing the angular dependence of scattering via wavelength equalization. Continuous angular spectrum is obtained without mechanical scanning enabling single-shot measurement. Using this information, particle morphology can be determined with improved accuracy. We derive and experimentally verify an analytic wavelength-to-angle mapping model, facilitating rapid data processing. As a proof of concept, we demonstrate the method's capability of distinguishing differently sized polystyrene beads. The combination of this technique with time-stretch dispersive Fourier transform offers real-time and high-throughput (high frame rate) measurements and renders the method suitable for integration in standard flow cytometers.