Potentialities of flexoelectric effect in soft polymer films for electromechanical applications

International audienceAmong the transduction mechanisms of interest for sensing and/or actuationapplications at nano/micro scale, the piezoelectric effect has been widely exploited owing tothe solid state nature of piezoelectrics, the large ability of specific classes of materials for themechanical-to-electrical energy conversion and easy integration. However, every piezoelectric(also generally ferroelectric) presents well-known intrinsic drawbacks such as required polingstep and related aging. In contrast, uniquely flexoelectric materials do not suffer from thesedisadvantages because flexoelectricity, a universal effect in all dielectric solids defined as theelectrical polarization induced by a strain gradient, does not imply preliminary electric fieldinducedmacroscopic polarization. Besides, strain gradient may be easily obtained by bendingplate or cantilever-shaped structure and in this case it is nothing but the local curvature of theflexible system. Thus, as strain gradient (curvature) inversely scales with both elastic stiffnessand thickness, this study will focus on the evaluation of the potentialities of flexoelectric effectin soft polymer films for electromechanical applications, with an emphasis on the thicknessinfluence. In this way, analytical results combined to experimentally obtained effectiveflexoelectric coefficients for some typical polymer classes may provide guidelines for thedevelopment of soft and low frequency flexoelectric mechanical transducers