Is It Really Possible to Power Miniaturized Implantable Biosensors with Ethanol Fuel Cells?

In the field of precision medicine, advancements in electronics and microfabrication have significantly enhanced interest in miniaturized implantable biosensor devices. These devices convert biological responses into electrical signals and are used in various medical applications, including continuous patient monitoring and diagnostics. The concept of “Body Dust” emerges as a novel approach to implantable and wearable sensors, envisioning a network of thousands of sub-micrometer sensors that provide detailed information about a patient’s metabolism from within their bloodstream. One of the primary challenges is powering these sensors. Onboard batteries would increase the device’s size and require future replacements. Therefore, alternative power solutions are crucial. Energy harvesting methods, such as optical light or piezoelectric energy, have been explored while maintaining the device’s small size and power constraints. Additionally, biofuel cells are considered a promising alternative to wireless power transfer methods, like ultrasound or inductive powering. Biofuel cells convert chemical energy into electrical energy through biochemical reactions, providing substantial power and ensuring biocompatibility for long-term use in medical applications. This study aims to identify the most efficient type of fuel cell for Body Dust applications, focusing on optimizing power output. A literature review compared different fuel cell types based on their fuel, such as glucose, methanol, and ethanol. Ethanol fuel cells demonstrated superior performance, particularly in power density. This research focused on designing and optimizing an alkalineacid ethanol fuel cell prototype. Several laboratory experiments determined the optimal electrode type and electrolyte concentration. Screen-printed platinum and carbon electrodes were tested, with catalysts like Pt/C and Pd/C used to enhance performance, facilitating characterization of both the anode and cathode. The optimized configuration used a screen-printed platinum anode with Pd/C catalyst ink, immersed in a 1M Ethanol and 1M Sodium Hydroxide solution. The cathode used a screen-printed platinum electrode in a 0.5M Hydrogen Peroxide and 1M Sulfuric Acid solution. Experimental characterization confirmed the effective performance of the prototype, with an open-circuit voltage of 1.14 V and a peak power density of 35.36 µW/cm2 at around 0.6 V. From this early prototype, considering optimal conditions and a chip-sized structure on the micrometer scale, an output power of 35.36 pW was generated. The biosensor currently requires 10 nW, but ethanol fuel cells documented for industrial use, on which this prototype is based, have the potential to deliver hundreds of nanowatts. These promising results open possibilities for using ethanol fuel cells in biomedical applications like Body Dust. Future work should focus on encapsulating the fuel cell within a fully biocompatible compartment and optimizing materials to miniaturize the system further, driving innovation in next-generation implantable devices.