A novel Lamb-mode liquid sensor array

The present paper demonstrates applicability of high-order Lamb modes for liquid sensing. It is shown that attenuation of the modes due to liquid loading depends on the mode polarization at the plate surface and the mode order. Plate modes with one, two and three surface displacements, propagating along the same direction, were numerically predicted and experimentally detected. A new type of modes with a dominant longitudinal displacement over entire plate thickness and propagation velocity equal to that of longitudinal bulk wave was discovered. On the basis of the modes of different orders a novel sensor array with a characteristic response pattern for a given liquid is suggested and tested using ST, x-quartz plate, 1.485 wavelength thick. Each mode of the array behaves as an individual sensor, operating at relevant frequency; amount of the "sensors" equals to the number of the modes generates in the plate.