Molecular Origin of Piezoelectricity and Flexoelectricity in Flexible Crystals

Many practical applications of molecular piezoelectric materials are curtailed by their mechanical brittleness and limited electromechanical coupling efficiency. Here, we report high longitudinal piezoelectric coefficients in two mechanically flexible crystals derived from amino acid analogues, with the piezoresponse linked to the molecular arrangement. Using a combination of micro-focused X-ray diffraction (µ-XRD) and high-pressure crystallography (HP-XRD), we uncover the origins of their piezoelectric behavior and establish a direct correlation between bending-induced structural distortions and flexoelectric polarization. Despite its fundamental importance, flexoelectricity—polarization arising from strain gradients—remains unexplored in organic crystalline materials. Our X-ray diffraction–based methodology combines spatially resolved structural mapping from µ-XRD with stress–strain analysis from high-pressure crystallography, enabling the quantification of both piezoelectric and flexoelectric responses through direct structure–property correlations. Beyond advancing the characterization of electromechanical properties, these results point to a material design strategy that integrates supramolecular helicity with mechanical flexibility, offering a blueprint for next generation organic electromechanical materials.