Angular resolved scattering microscopy

Abstract

The analysis of particle size and structure without any manipulation by exogenous markers is essential for investigating biological cells and tissues. For this purpose we built up a scattering microscope and already proofed that spectral resolved scattering microscopy is suitable to detect differences in sphere diameters of a few nanometers. Using an angular resolved scattering microscope permits to distinguish diameters of single polystyrene spheres with a standard deviation of less than 1 %. The setup consists of an inverse microscope with a reflected darkfield illumination that is realized by a collimated beam with a well-defined angle. A supercontinuum laser in combination with an acousto-optic tunable filter allows wavelength tuning of free choice. For validation we measured single polystyrene beads at different wavelengths and determined the diameters by correlating measurements of the scattered light with the theoretical angular distribution based on Mie theory. The average diameter of a single polystyrene bead was determined with a relative standard deviation of 0.65 %.