Beyond-Classical Ferroelectric Metamaterials: 3D-Printed Planar Lattices With Programmable Electro-Thermo-Mechanical Coupling.

Conventional porous ferroelectric materials often improve voltage-related figures of merit at the expense of piezoelectric charge coefficients. Here, we establish a topology-polarization co-design strategy for planar lattice-based ferroelectric metamaterials, which integrate underlying geometry, deformation mode, and polarization direction to program thermo-electromechanical responses. Beyond asymptotic homogenization, an analytical model is developed to correlate the effective ferroelectric properties with geometric parameters, and subsequently validated through experiments. Four representative planar lattices with distinct nodal connectivities, spanning stretching- and bending-dominated deformation modes, are explored under transverse and longitudinal polarization conditions. The transversely polarized triangular lattice exhibits an enhanced d33, which increases as the truss inclination angle θ decreases, and reaches approximately twice that of the dense material at θ = 30°. Programmable transverse and shear piezoelectric charge coefficients are achieved, enabling the hydrostatic charge constant to exceed four times that of the solid material and d24 to reach approximately twice the bulk. Owing to the substantial reduction in relative dielectric constant and heat capacity at low relative density, the pyroelectric voltage figure of merit reaches 43 × 10-3 m2/C, more than eight times that of the bulk material. These architected ferroelectric metamaterials offer a promising platform for realizing efficient multifunctional sensing and human-machine interfaces.