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Rational design of anode surface chemistry in microbial fuel cells for improved electron transfer. (Army Research Office - PI Schuler, Co-PI Ista)

Microbial fuel cells (MFCs) represent a developing technology that can provide waste biodegradation while generating a low voltage electric current. Transfer of electrons from exoelectrogenic bacteria to and from anodes and cathodes is a key feature of microbial fuel cells. Our project seeks to gain a better understanding of how anode and cathode surface characteristics, such as surface energy and chemical composition, affect electron transfer, with the overall goal of improving the activity and stability of these systems.

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Attachment of gold nanoparticle with differing surface chemistries to S. oneidensis. A. Bare gold. B. Amine. C. Carboxylic acid. D. Methyl. Scale bars A,B =2mm, C=5mm, D=1mm.

Specifically, our lab has focused on surface energy characterization of the common exoelectrogen Shewanella oneidensis and observing its interactions with self-assembled monolayers (SAMs) of alkanethiols on gold surfaces to evaluate the effects of specific chemistries on electron transfer. We are currently observing initial bacterial attachment and colonization of SAMs in stationary cell suspensions as well as bacterial suspensions subjected to flow, which mimic the conditions of a flow-through microbial fuel cell. S. oneidensis is a poor biofilm former in typical MFC conditions. We are also studying the attachment of SAM-modified gold nanoparticles to the S. oneidensis surface to determine which surface structures are most relevant to which chemistry and we are examining the effect of substratum chemistry on surface motility, a key process in successful biofilm formation. We have found that 100 nm gold nanoparticles with different surface chemistries attach to different parts of the S. oneidensis cell (See figure) and to different species of bacteria in different patterns. Furthermore, we have shown that S. oneidensis exhibits both swarming and twitching surface motilities and that these processes are effected by substratum chemistry. This research will improve our understanding of S. oneidensis surface colonization and will be used to improve the efficiencies of microbial fuel cells by creating modified surfaces for anode materials. In the near future, we will observe how these various SAM surfaces affect electron transfer of S. oneidensis by utilizing electrochemical characterization techniques.

A. Grant and K. O'Neill, Legend of the Dark Mite, Batman: Legends of the Dark Knight, (1989)