Topology-driven electromechanical actuation in 3D-printed TPMS piezoelectric ceramics

In this work, we demonstrate auxetic actuation in fully sintered, lead-free piezoelectrics structured by triply periodic minimal surfaces (TPMS). Using high-resolution additive manufacturing, we fabricate monolithic K 0.5 Na 0.5 NbO 3 ceramics with internal electrodes conformally integrated along the surfaces. The embedded electrode configuration within the piezoelectric ceramic ensures a nearly uniform volumetric electric field distribution, enabling more efficient activation and significantly lowering the required driving voltage compared to conventional lattices with external or non-integrated electrodes. The metamaterial auxetic properties of these structures arise directly from the coupling between the transverse piezoelectric effect and the geometric properties of TPMS. We validate the structure-function relationship through finite element modelling, interferometric displacement mapping, and hysteresis analysis across multiple TPMS types. The effective properties of the electroactive architectures are formulated, and the influence of geometric parameters on dedicated figures of merit is analysed using a nonlinear electromechanical model. This approach establishes a geometry-driven, electrode-integrated design platform for high-performance 3D ceramic actuators, suitable for applications such as adaptive optics and reconfigurable microsystems.