PI Alan Russell
Co-Investigators Richard Koepsel
Title Miniature Biofuel Cell from Gold Microfiber Electrodes
Description Evolving research on implantable sensors, drug-delivery systems and other power consuming implantable devices like pacemakers and insulin pumps requires the matching development of power sources that can be used together with the implantable device. A great deal of research performed on miniature, lightweight, long-lived batteries resulted in the development of the small lithium ion battery . The common battery is an energy source that contains reacting chemicals securely encased in an impermeable cell, and provides only the electrical leads to connect to devices. Current lithium iodide pace maker batteries have an open circuit voltage of 2.8 V, weigh about 13 g and have a relatively large volume of 5-8 ml.  Cardiac pacemaker battery design poses a number of special challenges including: the development of biocompatible materials; prevention of corrosion; preventing leakage of the contents; ensuring high reliability; and accurate determination of the end of the battery life. Many of these concerns and many of the inherent risks involved in battery replacement could be alleviated with a longer lasting biomimetic power source.
Another example is the insulin pump where most modern models are external and operate on common batteries that need to be replaced every 3-4 weeks. Many of the limitations of batteries can be eliminated by replacement with a fuel cell. A fuel cell has reactants that are fed from external reservoirs to the power cells. A biofuel cell based on enzymatic redox reactions which uses reactants that are always present in vivo holds great potential in applications and devices that would benefit from implantable power sources. A biofuel cell can be made smaller than batteries that require containment, would be biocompatible and environmentally friendly, could potentially run indefinitely, and can produced be cost-effectively.
The biofuel cell consists of an anode containing an oxidizing enzyme, typically glucose oxidase (GOX), and a cathode containing a reducing enzyme, usually either laccase or bilirubin oxidase (BOD). The fuel for the power generation is glucose which is oxidized by GOX to gluconolactone and hydrogen peroxide resulting in a 2 electron transfer to the electrode. The electrons flow from the anode to the cathode and are utilized by the reducing enzyme, laccase or BOD, to reduce dissolved oxygen to water.
The literature provides many examples of biofuel cells with different configurations of enzyme immobilization and electron shuttling mechanisms between enzyme and electrode [3-7]. The reported configurations suffer from several limitations: (a) Limited supply of oxygen to the cathode thus the power output is lower than the theoretical value ; (b) The electron transfer between the enzyme and the electrode is facilitated by the use of an electron mediator, either soluble or immobilized on the enzyme or on surrounding supporting polymer and these mediators are most often highly toxic species such as osmium complexes ; and (c) The size of the electrode is most often large (several centimeters in both diameter and length) and while reduction of the electrode size is possible it is most often accompanied with lower amounts of immobilized enzyme  and correspondingly lower power. Thus, the overall performance of biofuel cells is far from optimal, and inhibits the application of the fuel cells in implantable devices.
Source National Science Foundation
Term 05/01/11 – 04/30/13
Amount Direct: $132,693
IDC = $67,307