Radiofrequency Encoded Angular-Resolved Light Scattering

Label-free classification of microstructures is a valuable approach in a variety of fields including cytometry and atmospheric science. The sensitive classification of microscopic cells and organisms is especially an important outstanding problem in biology. Flow cytometry is a routine method for cell classification. Current flow cytometers use light scattering at two fixed angles to infer information about size and internal complexity of cells at rates of more than 10,000 cells per second. However, this approach limits the precision and information that can be deduced by the cell population from the light scattering patterns. Capturing the full angular scattering spectrum of cells and particles would enable classification of cells with higher resolution and specificity. By capturing the angular dependence of scattering intensity we will be able to extract information about the scattering particle, hence providing a label-free method for particle classification. Current systems that provide angular scattering patterns do not have the throughput required to be implemented in state-of-the-art flow cytometers. Inverse scattering has been one of the more difficult problems to solve in electromagnetic wave interaction problems. Yet there have been many solutions obtained by analytical and computational modeling for various cases. The angular light scattering profile of particles is dependent on their morphological parameters, such as size, shape, and their internal structure. One of the most interesting applications of modeling these scattering profiles is in characterizing cells to identify abnormalities. Methods to take advantage of this angular dependent information have been demonstrated, however, these methods have various limitations such as low speed and precision. Here I present a new high throughput multi-angle resolved light scattering measurement technique that is able to capture the full angular scattering profile of particles in a single shot using a single detector. Termed Radiofrequency Encoded Angular-resolved Light Scattering (REALS), this technique uses one-to-one radiofrequency-to-angle mapping to measure angular dependence of light scattered from particles in a single shot using a photomultiplier tube. Using this technique it is possible to capture the continuous scattering profile over a wide dynamic range without mechanical scanning. This information allows us to characterize particle morphology and size with increased accuracy and high throughput, enabling label-free and high speed flow cytometry. As a proof of concept we distinguish the radius of tapered silica fiber over a range of radii