The flexoelectric effect of solids represents a new branch of research. As an electromechanical conversion mechanism, it occurs in all dielectric materials. This offers new applications based on a large number of possible materials. Based on that, an investigation of properties and conversion conditions are of great importance. It is important to find out the significance of flexoelectric energy conversion in relation to other conversion mechanisms. This paper attempts to verify the flexoelectric effect in simple dielectric materials and to investigate the applicability in the area of energy harvesting (EH). In our studies, dielectric Polyethylene-Terephthalate (PET) polymer films were used in two different plate capacitor configurations. Two different measurement setups were built to enable the evaluation of polymer films under changing conditions. Main verification parameter of the energy conversion is the electrical voltage change in a differential measurement setup. Changing strain gradients, the basis of the flexoelectric conversion, were generated in two separate ways in thin PET-films. First results clearly show the presence of flexoelectric conversion. The height of the voltage pulses by mechanical loading of the samples cannot be explained by capacitive energy conversion only. Another effect is required to explain the electrical response - FLEXOELECTRICITY
Flexoelectricity is a relatively new phenomenon in research. It bases on a change in polarization caused by changing mechanical strain gradients in dielectric materials. Flexoelectricity is present in all dielectric materials. Different other energy conversion principles are used in energy harvesting or sensor applications. The flexoelectric effect of solids is in a very early stage of research and still far away from practical applications at the moment. Achieving electrical signals by flexoelectric conversion requires changes of mechanical strain gradients in dielectric materials. To generate that, not simple but more complex structures are needed. Furthermore, flexoelectricity of solids is not completely understood yet. Additional investigations in this area of research are necessary to prove the usability of this effect. This paper starts with investigations in this field and discusses a first approach for using the flexoelectric effect from an application-based point of view. As dielectric material, Polyethylene-Terephthalate (PET) polymer films were used in a plate capacitor configuration. A complex measurement setup was built to enable the evaluation of polymer films under changing conditions. The main parameter to verify an energy conversion is the change of system capacitance. First results show a small change in capacitance with time and a capacitance difference dependency on the movement frequency of actuation.