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

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 ScxAl(1–x)N films deposited by sputtering technique onto polyimide substrates, assessing their piezoelectricity and biocompatibility. Flexible ScxAl(1–x)N films have been analyzed in terms of morphological, structural, and piezoelectric properties. ScxAl(1–x)N layer exhibits a good surface roughness of 4.40 nm and moderate piezoelectricity with an extracted effective piezoelectric coefficient (d33eff) 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 ScxAl(1–x)N films with human cell lines, shows that this material does not have significant effects on tested cells. Furthermore, the ScxAl(1–x)N layer, integrated onto a flexible device and analyzed by bending/unbending measurements, shows a peak-to-peak open-circuit voltage (VOC) of 0.32 V and a short-circuit current (ISC) of 0.27 μA, with a generated power of 19.28 nW under optimal resistive load, thus demonstrating the potential of flexible ScxAl(1–x)N films as active layers for next-generation wearable/implantable piezoelectrics.