UC San Diego

Considerable efforts in research have been dedicated to the advancement of enzyme-based biofuel cells (BFCs) for various applications. BFCs can be used as energy-conversion devices, converting biofuels into electricity. Self-powered biosensors can also be engineered from BFCs. Such self-sustainable BFC-based biosensors and bioelectronics open opportunities for various biomedical applications, ranging from wearable, ingestible, to implantable applications. However, irrespective of purposes, bioelectronics mandates sustainable energy sources. The goal in the research is to expand the spectrum of new BFCs for biomedical technologies. Valuably, BFCs working as self-powered biosensors and energy harvesters simplify overall systems by minimalizing energy-consuming compartments, allowing the miniaturization of biodevices that traditional devices cannot enable. This dissertation describes an example of the first textile-based BFCs as stretchable self-powered sensors that can autonomously extract the electricity from perspiration and use this electricity as an analytical signal to indicate metabolite levels. This successful demonstration of wearable self-powered sensors with real-time wireless communication is expected to step further the progress of energy-harvesting systems and self-sustainable bioelectronics. Moreover, this dissertation will describe the fully edible ethanol BFC, based merely on biocompatible mushroom/plant extracts and food-based materials without any additional external mediators. These edible BFC energy harvesters represent attractive opportunities for modernizing biosensors and bioelectronics for the use in the digestive system. Furthermore, the grand challenges of BFCs including oxygen dependency will be discussed. For example, this dissertation includes an approach to address the oxygen limitations by developing a nanocomposite of oxygen-rich cathode material to provide the internal oxygen for the BFC cathodic reaction. Therefore, the effect of fluctuating oxygen levels during the operation of BFCs can be mitigated. Understanding challenges and opportunities are significant to transform BFCs to new devices for diverse domains, such as wearable, ingestible, and biomedical technologies.