Chemical & Biomolecular Engineering Department of Chemical and Biomolecular Engineering University of Illinois University of Illinois at Urbana - Champaign
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Paul J. A. Kenis

Paul J. A. Kenis
Kenis Group Web Site

Contact Information:
e-mail:
phone: (217) 265-0523
fax: (217) 333-5052

115 Roger Adams Lab
MC-712, Box C-3
600 S. Mathews Ave.
Urbana, IL 61801

Associate Professor
M.Sc., University of Nijmegen, The Netherlands, 1993
Ph.D., University of Twente, The Netherlands, 1997
Postdoctorate, Harvard University, 1997-2000

Microchemical Systems: Microreactors, Microfuel Cells, and Microfluidic Tools

In modern science and engineering, some of the best opportunities for research come at the borders between existing fields. My program focuses on exploratory, multidisciplinary research in microchemical systems including stand-alone applications, such as microreactors and microfuel cells, as well as microfluidic tools that enable or facilitate other studies. The development of microchemical systems often entails more than mere miniaturization of macro or meso-scale systems. Designs need to be adjusted to account for, or even utilize, the characteristics of the microscale.

Micro Fuel Cells

We are pursuing the development of membraneless micro fuel cells in which two aqueous streams containing fuel and oxidant, respectively, flow side-by-side in a single microfluidic channel with the anode and cathode placed on opposing sidewalls. The occurrence of laminar flow at the microscale eliminates the need for the usual static barrier of a polymer electrolyte membrane (PEM). Advantages of the membraneless designs include the elimination of: fuel crossover, water management issues, and restrictions on media. Whereas most conventional PEM-based fuel cells are limited to operation in acidic media, these membraneless fuel cells can also operate in alkaline media, which enhances reaction kinetics at both the anode and cathode and thus overall fuel cell performance. Recently we have created an air-breathing variety of these microfluidic fuel cells, which reaches current densities and power densities similar to those of PEM-based direct methanol fuel cells. Presently we are integrating multiple of these fuel cells (scaling out, not up!) to show their promise for application as power sources in portable electronics.

Microreactors

Recently, we have reported on microreactors for the efficient electrochemical regeneration of cofactors such as NADH, which opens up the use of a much wider range of enzymes for biocatalytic processes in the synthesis of chiral fine chemicals. In these microfluidic reactors focusing of a reactant stream on one of the electrodes inside the microreactor shifts a normally unfavorable reaction equilibrium in the desired direction, and the lack of a bulk phase prevents the reverse reaction from taking place. Presently, we are extending these microfluidic reaction engineering concepts to other chemistries. We are also pursuing the development of ceramic microreactors for in-situ hydrogen production from liquid fuels with high energy density. These fuel processors may find application in the supply of hydrogen to hydrogen fuel cells while hydrogen storage and safety issues can be avoided. These microreactors are stable up to at least 1200 °C and are comprised of high-surface-area, porous SiC and SiCN monoliths covered with catalyst embedded in high density ceramic housings. Hydrogen can be produced efficiently from the decomposition of ammonia at 1000 °C and presently we are studying steam reforming of hydrocarbons.

Microfluidic Tools

Banking on the capability of microfluidic systems to apply different chemistries with micrometer resolution, we are developing various enabling microfluidic tools. For example, we have created evaporation-based platforms for the identification of suitable conditions for protein crystallization, and are presently enhancing these platforms to aid the crystallization of membrane proteins. Similar tools can be used for the more fundamental study of crystal nucleation and growth. In a different set of microfluidic tools we create gradients in chemical composition in solution and on surfaces to enable the study of proliferation, differentiation, and migration of cells under the influence of external triggers (e.g. ECM proteins, growth factors, potential). In many of these highly multidisciplinary research projects, we work closely together with other research groups that are experts in the fields of application of this microfluidic technology.

Advancements in microfabrication and microfluidics

While pursuing the specific projects reported above, we also develop novel microfabrication methods. For example, we found a way to create multilevel microfluidic structures through single exposure photolithography. We also study the interplay of physicochemical phenomena such as diffusional mixing, reagent depletion, and flow reorientation effects for many of the different microchemical systems based on multistream laminar flow.

Selected Publications

Micro Fuel Cells:

R.S. Jayashree, M. Mitchell, D. Natarajan, L.J. Markoski, P.J.A. Kenis, A Microfluidic Hydrogen Fuel Cell with a Liquid Electrolyte, Langmuir, 23, 6871-6864 (2007).

R.S. Jayashree, L. Gancs, E.R. Choban, A. Primak, D. Natarajan, L.J. Markoski, P.J.A. Kenis, "Air-Breathing Laminar Flow Based Microfluidic Fuel Cell", J. Am. Chem. Soc., 127(48), 16758-16759 (2005).

R.S. Jayashree, D. Egas, D. Natarajan, J.S. Spendelow, L.J. Markoski, P.J.A. Kenis, "Air-breathing Laminar Flow-based Direct Methanol Fuel Cell with Alkaline Electrolyte", Electrochemical and Solid State Letters, 9(5), A252-256 (2006).

J. Yeom, R.S. Jayashree, C. Rastogi, M.A. Shannon, P.J.A. Kenis, "Passive Direct Formic Acid Microfabricated Fuel Cells," J. Power Sources, 160, 1058-1064 (2006).

Microreactors:

S.K. Yoon, C. Kane, E.R. Choban, T. Tzedakis, P.J.A. Kenis, "Laminar Flow Based Electrochemical Microreactor for Efficient Regeneration of Nicotineamide Cofactors for Biocatalysis", J. Am. Chem. Soc., 127(3), 10466-10467 (2005).

Christian, M. Mitchell, D.-P. Kim, P.J.A. Kenis, "Ceramic Microreactor for On-Site Hydrogen Production", J. Catalysis, 241, 235-42 (2006).

Christian, M. Mitchell, P.J.A. Kenis, "Ceramic Microreactors for On-Site Hydrogen Production from High Temperature Steam Reforming of Propane," Lab on a Chip, 6, 1328-1337 (2006).

S.K. Yoon, G. Fichtl, P.J.A. Kenis, "Active Control of the Depletion Boundary Layer in Microfluidic Electrochemical Reactors" Lab on a Chip, 6, 1516-1524 (2006).

Microfluidic Tools:

S. Talreja, P.J.A. Kenis and C.F. Zukoski, "A Kinetic Model to Simulate Protein Crystal Growth in an Evaporation-Based Crystallization Platform," Langmuir, 23, 4516-4522 (2007).

S. Talreja, D.Y. Kim, A.Y. Mirarefi, C.F. Zukoski, P.J.A. Kenis, "Screening and Optimization of Protein Crystallization Conditions through Gradual Evaporation Using a Novel Crystallization Platform", J. Appl. Crystallography, 38(6), 988-995 (2005).

R. Gunawan, J. Silvestre, H.R. Gaskins, L.B. Schook, P.J.A. Kenis, D.E. Leckband, "Cell Migration and Polarity on Microfabricated Gradients of Extracellular Matrix Proteins", Langmuir, 22, 4250-4258 (2006).

G. He, V. Bhamidi, S.R. Wilson, R.B.H. Tan, P.J.A. Kenis, C.F. Zukoski, "Direct Growth of γ Glycine from Neutral Aqueous Solutions by Slow, Evaporation-Driven Crystallization", Crystal Growth & Design, 6(8), 1746-1749 (2006).

M.W. Toepke, S.H. Brewer, D.M. Vu, K.D. Rector, J.E. Morgan, R.B. Gennis, P.J.A. Kenis, R.B. Dyer, "Microfluidic Flow-flash: Method for Investigating Protein Dynamics", Anal. Chem, 79, 122-128 (2007).

V.L. Kolossov, B.Q. Sprin, A. Sokolowski, J.E. Conour, R.M. Clegg, P.J.A. Kenis, H.R. Gaskins, "Engineering Redox-sensitive Linkers for Genetically Encoded FRET-based Biosensors," Experimental Biology & Medicine. 233, 238-248, (2008).

Microfabrication and Microfluidics:

C. Gupta, G.A. Mensing, M.A. Shannon and P.J.A. Kenis, "Double Transfer Printing of Small Volumes of Liquids," Langmuir, 23, 2906-2914 (2007).

M.W. Toepke, P.J.A. Kenis, "Single-Exposure Photolithography for the Fabrication of Multilevel Microfluidics", J. Am. Chem. Soc., 127(21), 7674-7675 (2005).

S.K. Yoon, M. Mitchell, E.R. Choban, P. J.A. Kenis, "Reorientation of the Interface between Two Liquids of Different Densities Flowing Laminarly through a Microchannel", Lab on a Chip, 5, 1259-1263 (2005).