SAW based phononic crystal liquid sensor - Periodic microfluidic channels approach

We report on practical realization of novel liquid sensor upon a base of typical SAW device design. The sensor is implemented as a periodic microfluidic structure atop a piezoelectric substrate. Simultaneous employment of phononic crystal phenomenon and structural resonance inside the phononic crystal is the basic idea behind. The phononic crystal band gap prevents propagation of traveling waves through the structure and their conversion and scattering into the substrate. The structural resonance enables acoustic signal amplification at frequencies predetermined by materials composing the structure. The sensor operates at high frequencies and potentially is capable to measure sound velocity and bulk viscosity of liquids with a precision superior to established instruments. The periodic microfluidic structure is made of SU-8 layers atop of lithium niobate based SAW device and acts as a liquid analyte container. It applies MEMS technology with a specific attention to the multilayer fabrication and exceptional parameters control. Experimental results demonstrate the feasibility of this approach providing a distinct and predictable sensor response on speed of sound of analyte.