Microbial Fuel Cells
2011 Seed Grant
Certain types of bacteria are known to release electrons as part of their metabolic activity. This phenomenon is the platform for Microbial Fuel Cells (MFCs), where bacteria, which attach to electrodes, can be used to generate an electrical current. Traditionally, MFCs are macro-scale batch units. However, recent studies have shown that electron transport occurs only in the first few layers of bacteria surrounding the electrodes (about 15 - 20 microns in thickness). Hence, for efficiency and space purposes, there is significant benefit in making small-scale MFCs where the surface to volume ratio is higher. The project is a collaboration with Professor Thomas DiChristina (School of Biology, Georgia Institute of Technology).
Assembled and ready to operate microbial fuel cell with the two Plexiglas plates together with the bare polydimethylsiloxane (PDMS) device. (Photo: Daniele Vigolo)
The methods and approach of microfluidics is a natural toolbox for this step. The framework of this Siebel Energy Challenge research project is to integrate MFCs in microfluidic devices, which consist of small channels with a typical size of few tens of microns. This approach will also allow precise control of the flow conditions of the nutrient medium and its influence on the bacteria behavior. One objective of the research project will be to achieve a continuously operating microfluidic MFC (steady current) in contrast to batch operation of an MFC, which is discussed in the recent research literature. Another objective is to leverage co-flow technology to try to replace the most expensive MFC component, which is the proton exchange membrane. The Stone research group already has several MFCs working in the laboratory.
MFCs can also be used to clean water since electricity-generating bacteria can consume contaminants in wastewater. During the 2012-2013 academic year, Stone and members of his group plan to design a MFC that uses an input of wastewater with no need of external power sources (i.e. by using gravitational and/or capillary forces) to enhance the applicability of such a device.
Educational Impacts
Members of the Stone group are developing interdisciplinary modules for mathematical modeling to enhance the applied mathematics course (MAE 305/MAT 301/EGR 305: Mathematics in Engineering I) required of all engineering undergraduates. Stone and colleagues are using the spirit of Pasteur’s Quadrant by D.E. Stokes as the intellectual framework and inspiration for integrating “considerations of use” (to use some of the language of Stokes) into a course traditionally taught in the spirit of "fundamental understanding and methods.” The materials are being specially developed for access via the web. This step is intended to readily link the mathematical ideas with real applications, as evidenced by links to pictures, videos, newspaper articles, journal articles, etc. For a given subject, a short reading (e.g. 2-3 pages) describing a problem along with a brief description of a mathematical model consistent with the topics discussed in lecture will be provided to the students. The students will then be expected to solve the mathematical model for a specific application and draw some meaningful conclusions.
The Microbial Fuel Cells project is naturally interdisciplinary with the need of a strong component of engineering skills. First, it involves soft lithography techniques to fabricate microfluidic devices. Second, it requires basic knowledge of biology to handle bacteria (growth, nutrients, etc.). Third, microscopy is essential in visualizing how and where bacteria bind to electrodes, and to study the mutual influence of environmental conditions (e.g., shear stress, voltage drop across electrodes, etc.) on the bacteria biofilm formation. Finally, setting up MFC experiments requires building basic electric circuits. All of these activities make ideal, energy-inspired undergraduate projects, which have the spirit associated with Pasteur’s Quadrant.
