Comprehensive Review on Flexoelectric Energy Harvesting Technology: Mechanisms, Device Configurations, and Potential Applications

Flexoelectricity is the electromechanical coupling between mechanical strain gradient and electric polarization or vice versa. This unique effect becomes considerable as the material dimension decreases and is found in a wide range of materials. In this review, flexoelectric effects in different dielectric materials and their characterization methods have been summarized. Also, the different mechanical structures for the measurement of electric outputs corresponding to different components of strain gradient are discussed. We have also discussed in detail the recent theoretical models developed in the field of flexoelectricity. Furthermore, the factors contributing to the effect such as various mechanisms of the flexoelectric response in ferroelectrics and affecting the effective flexoelectric coefficient have been highlighted. Along with providing a broad material choice, it has found vast potential applications in sensors, actuators, transducers, etc., and thus, a flexoelectric nanogenerator has proven to be an energy harvesting technique. The recent advances in flexoelectric energy harvesting techniques have been reviewed. Apart from these applications, we have given a brief report on the recent developments and other applications of the flexoelectric effect. Moreover, the recent discoveries in flexoelectricity that claim that this effect may promote the development of nanoelectronics have been summarized. At the end of the review, the future perspective of flexoelectric-based applications has been discussed.