3D-printed energy harvesting devices for flexible and wearable electronics

Ambient energy harvesting has great potential to contribute to sustainable development and address the emerging energy demands. Particularly, energy harvesting devices (EHDs) are attractive for powering self-powered wearable and smart electronics, where several challenges exist due to the use of traditional batteries. Despite the rapid advances in EHDs, their utilization in flexible and wearable self-powered electronics is limited due to traditional manufacturing processes. Solution-based 3-dimensional (3D) printing techniques have huge potential to improve the manufacturing of next-generation EHDs. This review focuses on the current status of 3D-printed EHDs for flexible and wearable devices. The inkjet printing and extrusion-based additive manufacturing processes can greatly improve the manufacturing of EHDs due to their capability to process a wide range of materials and design flexibility. Further, this review outlines the materials employed for fabricating different EHDs, such as piezoelectric nanogenerators (PENGs), triboelectric nanogenerators (TENGs), solar cells, and thermoelectric devices, and the recent challenges in their full utilization for flexible and wearable electronics. It also features recent notable results in the additive manufacturing of EHDs, existing challenges, and future scope. In general, the huge potential of 3D printing for the smart manufacturing of EHDs for next-generation self-powered wearable and implantable electronics has been summarized in this review.