Highly conductive EGaIn/silk fibroin ink for graphene 3D array structure micro-supercapacitors

Abstract Ink-based screen-printed processes are a practical approach for scalable fabrication of wearable electronics with cost effectiveness and high throughput. However, a few challenges persist with respect to the electronic conductivity and ions diffusion rate of such devices. In this study, we investigated an EGaIn/Silk fibroin (SF) ink and a screen-printed strategy to fabricate graphene 3D array structure Micro-supercapacitors (MSCs) based on high conductivity EGaIn collector. The EGaIn/SF ink, owing to the coordination and chelation between SF and EGaIn, shows excellent stability and can be used to fabricate conductive patterns on flexible substrates. Interestingly, these EGaIn patterns exhibit a novel conductivity recovery mechanism, including gravity deposition, evaporation induction, mechanical sintering, and EGaIn surface self-healing. Simultaneously, by adjusting screen meshes and accurately printing graphene ink, we obtained a graphene 3D array structure interdigital electrode on the EGaIn layer, which shows a large specific surface area and obviously multidirectional ion diffusion effect. As proofs, the resultant MSCs-100 delivered an outstanding areal (volume) capacitance of 35.72 mF cm−2 (10.26F cm−3) at a current density of 25 μA cm−2, remarkable flexibility and cycling stability. Moreover, we have realized the cycling stability characterization of integrated equipment, which holds great potential for application in future flexible and wearable electronics.