Flexoelectricity in wrinkled thin films

Flexoelectric effect tends to be more pronounced in thin films, where large strain gradients are easier to achieve. Large-area and tunable strain gradients can be introduced by inhomogeneous deformation in wrinkled thin films subjected to in-plane compression. The wrinkle-induced strain gradients can locally break the inversion symmetry of dielectrics and thus induce flexoelectricity. In this paper, an electromechanical coupling model is developed to theoretically deal with the flexoelectricity in wrinkled thin films. By minimizing energy, we redefine the amplitude, wavelength, and critical strain of the wrinkles with flexoelectricity in mind. The results obtained in the current work show that the available energy and stretchability of the wrinkled thin films can be improved by enhanced flexoelectricity in thinner films. Moreover, the wrinkle-induced flexoelectric polar pattern can be manipulated by compressive strain, providing a voltage-free strategy for mechanically modifying the polarity of dielectric materials. These findings pave the way for wrinkle-based microelectromechanical devices and applications.