Measurement of the light scattering of single and two particles captured with a microfluidic trap

Abstract

We have developed a novel light scattering measurement system based on a microfluidic trap to measure the elastic light scattering of micro-particles. The particles were captured from the sample suspension by a microfluidic chip with a hydrodynamic trapping, which were stably immobilized at the predetermined position by the pressure gradient and friction in the micro-channel. The trapped particles were illuminated by a He-Ne laser after refractive index matching, and a narrow-field photodetector designed by the spatial filter and a photomultiplier mounted on a homocentric rotating platform was used to detecting the scattering light. In this paper, we have improved this measurement system. By reducing the background scattering of microfluidic chip to improve the signal-noise ratio and using precise control, we measured the 23.75μm diameter polystyrene microsphere’s light scattering distribution, the results showed a good agreement on the trend with the curves of theoretical result. At the same time, using the microfluidic trap, we captured two particles (same size and different size) in a fixed orientation with touching components and obtained the light scattering distribution.