I.V. Anisimkin, Yu.V. Gulyaev, V.I. Anisimkin
Knowledge on real properties of liquid media and internal processes associated with chemical, biological, and physical transformations are currently needed for many branches of science and industry. Because of that, a number of electronic sensors based on various physical principles are developed in many countries. One of them, considering as most attractive, is relied upon acoustic wave propagation along interface between solid wafer and test liquid, penetrating the wave form the wafer into the liquid, and recording the changes in the wave amplitude or phase due to liquid loading. Usually, acoustic sensors operate at 10-100 MHz and acoustic amplitudes 1 nm. Typical thickness of the layer probed by the wave in the liquid is about 1 μm of interface.
This article reviews recent achievements in acoustic waves sensing. Different papers are classified both by mechanisms of the sensing (mass loading, electric loading, viscous interaction, thermal variation) and the type of the wave (Rayleigh, Lamb, shear-horizontal, leaky, bulk). As examples, the measurements of the liquid density, viscosity, dielectric permittivity, temperature, evaporation heat, evaporation rate, ion cell and virus concentrations as well as the real-time monitoring different processes such as acids dissociation, protein reactions, liquid-phase adsorption, phase-transitions, liquid heating, liquid cooling, droplet evaporation, seed germination, chemical and biological reactions are reviewed.
Finally, advantages and disadvantages of the acoustic wave sensing are discussed and probable outlooks are estimated.