Electrohydrodynamically printed solid-state Photo-Electro Protein micro-capacitors

The rapid development of portable and scalable electronics requires the production of high-performing, miniaturized energy storage devices with great flexibility and dimensional liberty. In recent years, printed capacitors have emerged as a promising means of meeting these demands. Printed flexible solid-state capacitors are being considered as next-generation energy storage systems because of their flexibility, portability, low cost, scalability, long cycle stability and the option of charging or discharging securely. Here we use sustainable and toxin-free photosynthetic protein complexes to fabricate solid-state flexible Photo-electro micro-capacitors as flexible power packs that are operable under indoor illumination. Electrohydrodynamic (EHD) printing was used to print biohybrid Photo-electro protein micro-capacitors that exhibited high performance uniformity and operational stability. Devices could be connected in either series or parallel configurations to modulate the operating voltage window and charge-discharge time. A specific capacitance of 110 mF g-1 was obtained at a scan rate of 10 mV s-1 and was retained at 91% of the initial value after 10,000 charge/discharge cycles at a current density of 0.063 mA g-1. Devices also displayed mechanical stability and robustness, retaining 93% of initial capacitance after 1000 cycles of bending. The data demonstrate that these micro-capacitors can deliver an economical and practical option as flexible energy storage and delivery devices for applications where exposure is primarily to indoor light.