Micro-Supercapacitors Based on Fungi-Derived Biocarbon Microfibers Infused with NiMoO Nanoparticles for Biomedical and E-Skin Applications

In various biomedical fields, noninvasive medical procedures are favored over invasive techniques, as the latter require major incisions or surgeries that cause bleeding, pain, and tissue scarring. The increased use of noninvasive biomedical equipment has created a demand for effective energy storage devices that are sufficiently compact to be used as a power source, easy to commercialize, and bio-friendly. Herein, we report the facile synthesis of nickel molybdenum oxide nanoparticle-infused biocarbon microfibers (NiMoO NPs@BCMFs) as a novel energy storage material. The microfibers were derived from the bracket fungus Laetiporus sulphureus. In a three-electrode system, the NiMoO NPs@BCMFs/nickel foam (NF) electrode delivered an areal capacity of 113 µAh cm⁻² at 1.5 mA cm⁻², with excellent cycling stability. Its capacity retention was 104%, even after 20,000 cycles. Bare BCMFs were also synthesized from the fungal biomass to fabricate a negative BCMFs/NF electrode. This, together with the positive NiMoO NPs@BCMFs/NF electrode, was used to construct a bio-friendly (hybrid-type) micro-supercapacitor (BMSC), which exhibited maximum energy and power density values of 56 µWh cm⁻² and 11,250 µW cm⁻², respectively. When tested for its ability to power biomedical electronics, the BMSC device successfully operated an electrical muscle stimulator, inducing potential signals into a volunteer in real-time application. Graphical abstract: (Figure presented.)