Fully transient stretchable fruit‐based battery as safe and environmentally friendly power source for wearable electronics

Power sources with good mechanical compliance are essential for various flexible and stretchable electronics. However, most of the current energy storage devices comprise of hazardous materials that may cause environmental pollution when improperly disposed. We show the first example of a stretchable, yet fully degradable battery made from nontoxic and environmentally friendly materials such as fruit‐based gel electrolytes and cellulose paper electrodes. The battery exhibits an areal capacity of 2.9 μAh cm−2 at 40 μA cm−2, corresponding to a maximum energy density around 4.0 μW h cm−2 at 56 μW cm−2 power density. The biomaterials constituted battery shows good mechanical tolerance to twisting, bending, and stretching while powering various electronic devices when combined with kirigami. Importantly, the entire battery disintegrates readily in phosphate buffered saline/cellulase solution. We integrate the “green” battery with various sensors in wearable healthcare devices for pulsation sensing and low‐noise surface electromyography applications.