Levitating Single Particles using Optical Trapping to Measure Circular Intensity Differential Scattering from Single Aerosol Particles for Detection and Identification of Bioaerosols

The phase function of circular intensity differential scattering (CIDS), specifically the normalized Mueller matrix element -S14/S11, has been used to distinguish biological and non-biological aerosol particles based on the detection of the helical structures of DNA molecules. In this work, we used optical trapping to levitate single particles in a custom-designed elliptical reflector. The reflector was used to collect the angle-dependent scattering signals, which can be completed in tens of µs. This approach required no lock-in amplifier, moving parts, or modulator needed, which are typically essential in the traditional experimental setups. The results demonstrated that we can obtain right and left CIDS simultaneously by the same optically trapped particle, which improves the efficiency of the detection of each individual particles containing biological molecules.