Microfluidics‐Assisted Fabrication of All‐Flexible Substrate‐Free Micro‐Supercapacitors with Customizable Configuration and High Performance

Abstract The rapid development of smart wearable microdevices has stimulated the urgent demand for micro‐supercapacitors (MSCs) with multiple form factors, however, several factors like conventional bulky stacked geometries, rigid substrates, and complex manufacturing processes have blocked their path toward practical application. Herein, a microfluidics‐assisted fabrication strategy is demonstrated which utilizes capillary action for precisely customising planar MSCs, showing substrate‐free configuration attributed to the use of polyvinyl alcohol hydrogel in both electrolytes and transfer template. Remarkably, the resulting MSCs with highly conductive polymer (PEDOT:PSS)‐based active materials as microelectrodes, exhibit excellent areal capacitance of 21.4 mF cm −2 and noticeable capacitance retention of 88% after 10000 cycles. Furthermore, the substrate‐free MSCs display extraordinary flexibility and remarkable stretchability of 640% strain. Significant serial and parallel integration is demonstrated for boosting voltage and capacitance output, demonstrative of impressive performance uniformity and applicability for different scenarios. Therefore, the exploration of microfluidics‐assisted fabrication is shown to be a reliable strategy for high performance standalone microelectronics with in‐plane configuration.