Piezoelectricity and Biocompatibility of Flexible ScxAl(1- x)N Thin Films for Compliant MEMS Transducers

Abstract

There is huge research activity in the development of flexible and biocompatible piezoelectric materials for next-generation compliant micro electro-mechanical systems (MEMS) transducers to be exploited in wearable devices and implants. This work reports for the first time on the development of flexible Sc_xAl_(1-x)N films deposited by sputtering technique onto polyimide substrates, assessing their piezoelectricity and biocompatibility. Flexible Sc_xAl_(1-x)N films have been analyzed in terms of morphological, structural, and piezoelectric properties. Sc_xAl_(1-x)N layer exhibits a good surface roughness of 4.40 nm and moderate piezoelectricity with an extracted effective piezoelectric coefficient (d₃₃^eff) value of 1.87 ± 0.06 pm/V, in good agreement with the diffraction pattern analysis results. Cell viability assay, performed to study the interaction of the Sc_xAl_(1-x)N films with human cell lines, shows that this material does not have significant effects on tested cells. Furthermore, the Sc_xAl_(1-x)N layer, integrated onto a flexible device and analyzed by bending/unbending measurements, shows a peak-to-peak open-circuit voltage (V_OC) of 0.32 V and a short-circuit current (I_SC) of 0.27 μA, with a generated power of 19.28 nW under optimal resistive load, thus demonstrating the potential of flexible Sc_xAl_(1-x)N films as active layers for next-generation wearable/implantable piezoelectrics.

Keywords: flexible devices; micro electro-mechanical systems (MEMS); piezoelectric materials; scandium aluminium nitride films; transducers.