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

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.