Series-connected flexible biobatteries for higher voltage electrical skin patches

A totally organic, flexible higher voltage enzymatic biobattery is demonstrated by series connection of carbon fabric-based biobatteries composed of a fructose dehydrogenase-modified anode and a bilirubin oxidase-modified cathode. The fructose/O₂ biobattery was divided and connected so as to maintain the original size (total electrode size: 2 cm²). The series-connected four quarter biobatteries showed increased voltage and current (0.6 V, 30 μA → 1.5 V, 80 μA) for an external load of 20 kΩ, which is a typical skin resistance. The divided batteries were put inside a flexible ion-insulating frame to avoid short-circuit between cells and electrically connected by soft hydrophobic leads that prevented ionic connection by wetting. Because the developed higher voltage biobattery maintains its small size and flexibility, it can even be put on a finger joint and serve to drive a wrist watch.