Microfluidic heater assisted by Rayleigh Surface Acoustic Wave on AlN/128°Y-X LiNbO3 multilayer structure

In this paper, we present a new microdroplet device assisted by Rayleigh Surface Acoustic Wave (R-SAW) for discrete microfluidic applications and biological reactions where microdroplet heating is needed. A multilayer structure is reported which consists to bury the Inter-digital Transducers (IdT) under a sputtered Aluminium Nitride (AlN) layer to electrically insulate. Thus, microdroplets can be deposited directly on the IdT, which improves the efficiency of the device. Indeed, effect of AlN layer on 128°Y-X cut lithium niobate (LiNbO₃) substrate is studied. Based on simulations, we show that electromechanical coupling coefficient can be enhanced with AlN layer leading to a better heating of microdroplet. Heating is next studied as a function of liquid viscosity and AlN layer thickness.