(71l) Laminar Flow Based Electrochemical Microreactor

The concept of a laminar flow-based electrochemical microreactor that utilizes the occurrence of laminar flow in microfluidic channels to achieve the necessary compartmentalization of the reductant and oxidant streams in a single channel without a physical barrier such as a membrane has been introduced. Two specific examples were explored using laminar flow-based electrochemical microreactors: (i) Membraneless microfluidic fuel cells in which the fuel and oxidant streams are kept separate by flowing laminarly in parallel rather than by a polymer electrolyte membrane [1]; (ii) Microreactors for regeneration of nicotinamide cofactors for biocatalysis that can only be pursued at the microscale due to the ability to focus a stream of reactants closely to the electrode utilizing multistream laminar flow [2]. Diffusional mixing of the two or more streams in these electrochemical microreactors still can be detrimental to their performance. To circumvent these issues, we recently integrated a porous separator into a laminar flow-based electrochemical microreactor. This separator minimizes the inter-diffusion width while the system still takes advantage of the characteristics of the microscale. A second challenge for laminar flow-based electrochemical microreactors is the formation of depletion boundary layers on the electrodes. Through the integrated of chaotic micro mixers (see Stroock et al., Science 2002) we have been able to continuously replenish of the boundary layers on the electrode of the microreactor, thereby increasing the conversion rates in both applications.

[1] See for example: (a) Micro-Fluidic Fuel Cell Based on Laminar Flow. E.R. Choban, L.J. Markoski, A. Wieckowski, P.J.A. Kenis, J. Power Sources, 2004,128, 54-60. (b) Air-Breathing Laminar Flow Based Microfluidic Fuel Cell, R.S. Jayashree, L. Gancs, E.R. Choban, A. Primak, D. Natarajan, L.J. Markoski, P.J.A. Kenis, J.Am.Chem.Soc., 2005, in press. [2]Laminar Flow-Based Electrochemical Microreactor for Efficient Regeneration of Nicotineamide Cofactors for Biocatalysis, S.K. Yoon, C. Kane, E.R. Choban, T. Tzedakis, P.J.A. Kenis, J.Am.Chem.Soc., 2005, 127(30), 10466-10467.