Separation of Microparticles using Optical Whispering Gallery Mode (WGM) Resonances

Phenomenon of WGM resonances has been known for millennia from acoustics; domes of many cathedrals are famous for it, where silent sound can travel multiple times around the circumference. In optical WGM resonators (e.g. microspheres) light in resonance may travel around the resonator for more than a million of times. One of the properties of such a resonance is giant amplification of the light propelling forces that can move microparticles 5 to 50 microns in diameter microparticles by distances up to 0.2-0.4 mm. We report on the progress in our attempt to harness this phenomenon for selecting and separating microparticles. Our goal is to develop an optical microfluidic cell, where evanescent light from the tapered down to 1 micron in diameter optical fiber would capture and transport to a separate chamber suspended in water microspheres whose WGM resonance is matching the light wavelength. Such method may find applications in photonics, biomechanics, and medicine.