Wednesday, July 27, 2011: 9:00 AM
Nottoway, 4th fl (Sheraton New Orleans)
We investigate thin adhesive coatings of reactive microorganisms on flexible substrates to engineer advanced composite, bioelectronic or photoreactive materials for energy generation. Optimization of the reactivity of microbial coatings depends on coating microstructure (nanoporosity, adhesion, packing), physical intensification (cell density/ surface area), and reduction of diffusion path (thinness). Up-regulation of gene expression of coating-entrapped microbes can further increase reactivity and allow coatings to adapt or “self-tune” to changing conditions. In order to optimize, model and predict the reactivity of multi-layer and multi-organism coatings, we study the microstructure of uniform monolayer coatings of polymer particle + cell blends deposited onto polyester substrates by convective sedimentation assembly (CSA) and dielectrophoresis (DEP). CSA orders cells on surfaces by evaporation of the meniscus; coating microstructure is effected by evaporation rate, sedimentation, and particle or cell properties (size, density, buoyancy, charge) combined with convective transport. DEP aligns microbes in an electric field as charged polarizable particles. CSA and DEP methods used for ordering polymer particle are being modified to screen polymer emulsion + cell blends to generate permanent cell adhesion to the substrate and preserve reactivity after drying. Model systems investigated are: anoxic H2 gas production by Rhodopseudomonas palustris, CO2 adsorption and O2 evolution by coatings of Chlamydomonas reinhardtii or Synechococcus sps. Understanding the relationships between coating microstructure and reactivity will lead to approaches to engineer highly reactive composite devices which incorporate both H2 and O2 producing microbial coatings (fuel cells), or COx adsorbing coatings for recycling carbon emissions to liquid fuels or chemical intermediates.