(Invited) Enzymatic Biofuel Cells Toward the Development of Wearable and Edible Bioelectronic Technologies

Abstract

Enzymatic biofuel cell (BFC) devices —‘green’ energy converters— can be used as new biomedical devices, self-powered biosensors, and energy sources. State-of-the-art wearable sensors can noninvasively monitor biomarkers (such as in sweat), while ingestible devices can detect biomarkers and monitor in vivo physiology with unique capabilities to directly access the gut environment during the passage of swallowable devices along the gastrointestinal tract. However, irrespective of applications, all bioelectronics mandate viable energy sources. Therefore, our efforts have been devoted to expanding the spectrum of applied aspects of BFCs for biomedical technology. BFCs used as self-powered biosensors can simplify sensing systems by minimizing power-consuming units. Such a unique feature allows two‐electrode BFC-based electrochemical sensors to operate without externally applied voltage, which enables the miniaturization and convenient design of biosensors that traditional biosensors cannot offer. We have pioneered textile-based BFCs as highly stretchable self-powered sensors for wearable systems; these can autonomously extract the electrical power from perspiration to probe the sensing of metabolites (i.e., glucose and lactate). Such BFCs with judicious serpentine designs are fabricated using screen-printing of stress-enduring inks. Successful applicability to sock-based self-powered lactate biosensors with real-time wireless communication was also demonstrated, for the first time, on the human subject. These devices will step further the development of skin-worn energy harvesting systems, non-invasive sensors, and smart textiles. Furthermore, in order to expand a new spectrum of bioelectronics, we have demonstrated the first example of an edible ethanol BFC, based solely on highly biocompatible mushroom/plant extracts and food-based materials without any additional external mediators. The BFC anode and cathode materials consist of biocatalyst-rich mushroom and plant tissues, along with dietary charcoal and vegetable oils. These edible energy-harvesting BFCs provide great opportunities for revolutionizing ingestible bioelectronics and self-powered sensors for monitoring health and the digestive system.