Microfabrication techniques and scale-up by replication promise to transform classical batch-wise chemical laboratory procedures into integrated systems capable of providing new understanding and control of fundamental processes. Such integrated microchemical systems would enable rapid, continuous discovery and development of new products with the use of fewer resources and the generation of less waste. Additional opportunities exist for on-demand and on-site synthesis, with perhaps the first applications emerging in portable energy sources based on the conversion of hydrocarbons to hydrogen for miniaturized fuel cells.
Microchemical systems can be realized in a wide range of materials including stainless steel, glass, ceramics, silicon, and polymers. The high mechanical strength, excellent temperature characteristics, and good chemical compatibility of silicon combined with the existing fabrication infrastructure for microelectromechanical systems (MEMS) offer advantages in fabricating chemical microsystems that are compatible with strong solvents and operate at elevated temperatures and pressures. Furthermore, silicon-based microsensors for flow, pressure, and temperature can readily be integrated into the systems.
Microsystems for broad chemical applications should be discovery tools that can easily be applied by chemists and materials scientists while also having a convincing “scale-out” to at least small production levels. The interplay of both these capabilities is important in making microreaction technology successful. Perhaps the largest impact of microchemical systems will ultimately be the ability to explore reaction conditions and chemistry at conditions that are otherwise difficult to establish in the laboratory. Case studies are selected to illustrate microfluidic applications in which silicon adds advantages, specifically, integration of physical sensors and infrared spectroscopy, highthroughput experimentation in moisture-sensitive organic synthesis, controlled synthesis of nanoparticles (quantum dots), multiphase and heterogeneous catalytic reactions at elevated temperatures and pressures, and thermal management in the conversion of hydrocarbons to hydrogen.
Klavs F. Jensen is the Lammot du Pont Professor of Chemical Engineering and a professor of materials science and engineering at the Massachusetts Institute of Technology. He received his MSc degree in chemical engineering education from the Technical University of Denmark and his PhD degree from University of Wisconsin–Madison. Prior to 1989, he was a faculty member in the Department of Chemical Engineering and Materials Science at the University of Minnesota. His research interests revolve revolve around microfabrication, testing, and integration of microsystems for chemical and biological discovery, synthesis, and processing. Chemical kinetics and transport phenomena related to processing of materials for biomedical, electronic, and optical applications are also topics of interest, along with the development simulation approaches for reactive chemical and biological systems, specifically, simulation across multiple length and time scales.
Jensen is the recipient of an NSF Presidential Young Investigator Award; a Camille and Henry Dreyfus Foundation Teacher–Scholar Grant; a Guggenheim Fellowship; and the Allan P. Colburn, Charles C.M. Stine, and R.H. Wilhelm Awards of the American Institute of Chemical Engineers. He is also member of the U.S. National Academy of Engineering and a fellow of the Royal Society of Chemistry.
Jensen can be reached at the Massachusetts Institute of Technology, Department of Chemical Engineering, Room 66-566, 77 Massachusetts Avenue, Cambridge, MA02139, USA; tel. 617-253-4589, fax 617-258-8224, and e-mail [email protected].