3D printed architected shell-based ferroelectric metamaterials with programmable piezoelectric and pyroelectric properties

Porous ferroelectric materials with conventional pore topologies have shown enhanced multifunctional performance. Here, we introduce a novel design and fabrication route to realize shell-based ferroelectric metamaterials, including spinodoids and diamond shellulars, with previously inaccessible multiphysical properties using a customized piezoceramic additive manufacturing platform. The effective properties of ferroelectric spinodoid metamaterials are predicted by a modified homogenization method. Assisted by a convolutional neural network, their architecture-multiphysical property linkage is established. Unlike porous ferroelectrics, certain shell-based ferroelectric metamaterials retain a piezoelectric constant d33 identical to their solid ferroelectric materials even at relative densities, ρr, as low as 0.3. Extremely low dielectric constants are attained, leading to enhanced sensitivity to force and temperature fluctuations. For example, a lamellar spinodoid with ρr = 0.5 exhibits a giant piezoelectric voltage constant 0.178 Vm/N and up to 12 times higher voltage, in response to an impact load, than its fully-solid ferroelectric counterpart. We demonstrate how local voltage responses under multidirectional mechanical forces can be manipulated by capitalizing on the diverse transverse piezoelectric anisotropies and graded design. The programmability and multifunctionality of shell-based ferroelectric metamaterials open the door for their applications in high-performance pressure and thermal sensors and intelligent building blocks for smart infrastructures.