Side scatter light for micro-size differentiation and cellular analysis

High resolution 2D side scatter patterns from polystyrene beads were obtained by using an integrated microfluidic waveguide cytometer. A He-Ne laser beam was prism-coupled into a microfluidic chip, and waveguide modes were excited to illuminate a single scatterer. While immobilizing a single scatterer on chip in the observation window area, high resolution 2D scatter patterns were obtained by using a CCD array located beneath the microchip. This cytometer is sensitive to variations in both the refractive index and the size of a single scatterer. Fourier transforms of Mie simulation results from a single scatterer show that forward scattered light at large angles is optimal for micro-size differentiation. While side scatter light was reported to contain rich information about organelles in a single cell, we show here that side scatter light can be used to perform fast micro-size differentiation and cellular analysis. A cross section scan of the experimental scatter pattern gives an oscillation distribution of the scattered intensity. This oscillation has a frequency that is typical for a given micro-size scatterer. A Fourier method for quick micro-size differentiation is reported, based on the comparisons between the Mie simulations and the experimental results. Finite-difference time-domain (FDTD) simulations of single white blood cells in the waveguide cytometer are studied, which allows extraction of microstructural and nano-structural information from single cells.