Microspheres as sensors to measure instant refractive index variation during phase transition of low melting substances

Microspheres were used as sensors to perform real time in situ accurate measurement on the instantaneous refractive index/density variation during the liquid-solid phase transition of low melting substances. The measurements were carried by immersing microspheres in the substances in liquid state and analyzing their phase-contrast microscopic images during the phase transition from liquid to solid states. In this paper, the principle of the method and the experiments of using the method for different applications will be described.