Synchronous determination of the rheological and acoustic properties of fluids using an oscillating fiber sensor and an ultrasonic microscope with phase contrast

摘要

A new method based on a micromechanical sensor and ultrasonic microscopy with phase contrast (PSAM) has been developed for the investigation of the viscosity of liquids and the simultaneous measurement of the velocity and attenuation oflongitudinally polarized ultrasonic waves in the GHz-regime. The amount of liquid can be as small as 1μl. Irreversible processes caused by the destruction of microstructures in complex fluids or gels can be avoided due to the small sensor deflections inthe range of 1-100 nm. The method is based on forced oscillations of a thin glass fiber fully immersed in the fluid leading to the excitation of viscosity shear waves. The detection of the fiber oscillation is performed at the free end of the fiber byultrasonic microscopy with phase contrast. The changes of the attenuation of sound and changes in the sound velocity are simultaneously detected during these experiments. Examples for applications with respect to polymerizing fluids and other complexmicro-structured fluids as well as demonstrations for the resolution obtainable for the determination of the well-defined viscosity of simple liquids are given.