Advancements of Flexoelectric Materials and Their Implementations in Flexoelectric Devices

Flexoelectricity, a universal electromechanical coupling phenomenon, has triggered new feasibilities of advancements in functional materials, especially for nanoscale materials. The strong flexoelectric response is initially discovered in ceramic materials with high permittivity, and then the past decades have witnessed the expansion of flexoelectricity to a broader range of material systems including semiconductors, polymers, and soft elastomers, which in turn raise emerging applications of flexoelectricity. Moreover, flexoelectricity is demonstrated to be significantly enhanced in thin films and nanostructures where ultra-high strain gradients are easier to achieve, rendering flexoelectricity attractive for modifying the functional properties of advanced materials and devices at the nanoscale. To provide a comprehensive drawing of the above aspects, this review highlights the recent progress of flexoelectricity in diverse materials, covering the characterization of flexoelectricity, the fundamental mechanisms of the enhancement flexoelectric response as well as the multi-functional applications. Finally, some open questions and perspectives are presented, underlining the fascinating future of this field.