Light scattering into two fixed angles vs. angle-resolved measurements for characterization of single submicron particles

Abstract

Single particle identification and characterization based on scatter measurements is widely used in numerous biomedical applications. This scatter-based characterization approach implies a solution of the parametric inverse light-scattering (ILS) problem. The need for high-speed analysis limits the amount of collected scatter information and motivates maximum simplification of optical model of analyzed particles. We analyzed the capabilities and limitations of two existing approaches, based on measurement of either two scattering signals or angle-resolved patterns, applied to characterize single submicron particles. The standard flow cytometric approach is based on light scattering measurements into two fixed angles, forward and side scattering, which are further fitted by the Mie theory. We showed that corresponding ILS problem may have multiple solutions, and the procedure results in uncontrollable errors if the particle is not spherical. By contrast, angle-resolved scattering measurements have much larger information content at a cost of reduced analysis speed. This approach coupled with rigorous solution of ILS problem is shown to provide accurate identification and characterization of biological particles, including nonspherical ones.