Flexoelectric control of polarization in 2D materials

This review article provides an overview of polarization generation and control in two-dimensional (2D) materials through the flexoelectric effect. Polarization can be engineered across multiple length scales, from the atomic to macroscopic level, using surface corrugation, substrate deformation, and atomic force microscopy tip loading. The flexoelectric effect, which arises from the coupling between a strain gradient and polarization, can occur in all dielectric materials, but its influence becomes especially pronounced in 2D systems where large gradients are readily formed. Such coupling enables mechanically tunable functionalities, including charge modulation, photoresponse enhancement, and energy harvesting, offering a practical pathway for polarization control without external bias. In addition, this review addresses confounding effects, such as piezoelectricity, triboelectricity, and surface electrochemistry, and emphasizes that careful experimental design is crucial to accurately identify the intrinsic flexoelectric behavior in 2D materials.