Recent advances and perspectives of 3D printed micro-supercapacitors: from design to smart integrated devices

3D-printed micro-supercapacitors (MSCs) have emerged as the ideal candidates for energy storage devices owing to their unique characteristics of miniaturization, structural diversity, and integration. Exploring the 3D printing technology for various materials and architectures of MSCs is key to realizing customization and optimizing the performance of 3D-printed MSCs. In this review, we summarize the latest progress in 3D-printed MSCs with regards to general printing approaches, printable materials, and rational design considerations. Specifically, several general types of 3D printing techniques (their working principles, available materials, resolutions, advantages, and disadvantages) and their applications to fabricate electrodes with different energy storage mechanisms, and various electrolytes, are summarized. We further discuss research directions in terms of integrated systems with other electronics. Finally, future perspectives on the research and development directions in this important field are further discussed.