Piezoelectric Flexible Energy Harvester Based on BaTiO₃ Thin Film Enabled by Exfoliating the Mica Substrate

Flexible piezoelectric energy harvesters (f-PEHs) have exhibited significant potential as long-lasting self-powered sources or sensor devices, as they can generate reliable and repeatable electricity under harsh and tiny mechanical bending cycles without restraints anywhere and anytime. Herein, a new approach for transferring piezoelectric ceramic thin films onto a single flexible substrate via piecemeal elimination of the sacrificial mica substrates is proposed. The crystallized piezoelectric BaTiO₃ thin film on a rigid mica substrate with electrodes and passivation layers is peeled off by means of a physical delamination process using sticky tape as the remover. The film is then transferred onto a flexible polyimide substrate using a polymer elastomer as a support. The fabricated BaTiO₃ thin-film f-PEH successfully converts an open-circuit voltage of ≈0.5 V and a short-circuit current of ≈30 nA from repeated mechanical bending deformations. The energy generation mechanism and performance of the perovskite BaTiO₃ thin-film f-PEH is supported using finite-element analysis (FEA) with multiphysics simulations. The novel transfer techniques adopting the removal of sacrificial mica layers opens the door to various high-performance flexible and wearable applications based on all-inorganic materials.