Enhanced flexoelectric metamaterials through chiral curved ligaments design

Flexoelectricity, a phenomenon present in all dielectric materials, describes the coupling between strain gradient and electric polarization. Recent studies have explored structural design strategies to exploit flexoelectricity, giving rise to flexoelectric metamaterials that exhibit apparent piezoelectric responses. However, achieving a high effective piezoelectric coefficient in artificially designed flexoelectric metamaterials remains a challenge. In this work, three distinct chiral flexoelectric metamaterials with straight, arc-shaped, and semicircular ligaments are designed. The influence of geometric parameters on the mechanical and flexoelectric properties is systemically investigated through theoretical modeling and numerical analyzing. The results indicate that the effective piezoelectric performance is enhanced by increasing the structural compliance using curved ligaments. The thinner and longer ligaments with larger cylinder radii lead to enhanced response. On the basis of theoretical analysis, the flexoelectric metamaterials are fabricated using non-poled lead zirconate titanate ceramics, and show an apparent piezoelectric coefficient d₃₃^eff of 16.87 pC/N, validating the theoretical predictions. These findings provide new insights and potential pathways for exploiting flexoelectricity in the design of advanced piezoelectric materials and energy-harvesting systems.