Measurements of the phase transition and the average length of the density fluctuation under supercritical fluid using micromechanical resonators

This paper presents an original method to measure the phase transition and macroscopic density fluctuation of supercritical carbon dioxide using a resonant microcantilever beam. There is a significant reduction of the resonant frequency near the phase transition point where the density and viscosity of carbon dioxide exhibit large variations, while the vibration amplitude of the micromechanical resonator displayed a large shift up due to generation of microscopic density fluctuation. The average length of the density fluctuation of supercritical fluid could be calculated from this large shift of the vibration amplitude and the value is in the range of millimeter.