Peter M. Martin & Dean W. Matson
The objective of this project is to develop new and improved methods for fabricating microchannel devices using plastic and ceramic materials. Plastics are important candidate materials for microanalytical devices and other microfluidic applications where their advan-tageous thermal, electrical, and chemical properties can be exploited. Many plastics are also amenable to a wide range of microforming and machining methods, including laser micromachining and hot embossing, that will allow development of low cost microfluidic devices. Ceramic materials offer unique capabilities in high-temperature and/or corrosive microfluidic applications. In addition to structural applications, ceramic components can serve as thermal and electrical insulators or as catalyst supports. Developing microfabrication methods for ceramics and plastics is critical to the microfluidic applications being developed under the Microsystems Science and Engineering Initiative at PNNL.
Development of plastic microfabrication methods focused primarily on patterning two-dimensional plastic sheets and laminating them into three-dimensional microfluidic components. This effort was a continuation of prior years of effort in this area, where considerable potential had been demonstrated.
Efforts in the area of plastics fabrication during the past year were aimed at testing several plactic materials with a variety of characteristics. Many of these types of materials offer unique challenges in terms of their patterning and bonding properties.
Microchannel machining capabilities at PNNL were enhanced during the past year by acquisition of a third excimer laser micromachining station. The new Reso-netics Maestro machining station offers through-mask machining capabilities that supplement the direct-write laser machining processes that were previously available. The dual-wavelength, high-power excimer laser provided with the station allows machining of many plastics at 248 nm as well as metals, and many glasses at the 193-nm wavelength. The ability to machine through-mask offers the potential to mill microchannels in a wide range of materials in a single pass rather than requiring the multiple passes as was needed for the direct-write systems. Consequently, microchannel floor quality and milling speeds were greatly improved by using the through-mask machining process (Figure 1).
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| Figure 1. Comparison of 100-micron-wide microchannels laser-machined using (a) a multiple-pass direct-write process requiring 10 passes of a 10-micron laser spot and (b) a single-pass mask-machining process. Machining time for channel b) was roughly 10 percent of that required to mil channel a. | |
Ceramic microfabrication efforts were aimed at developing processes for producing laminated ceramic microchannel devices. This process is similar to one we developed for producing microchannel array devices in metals using diffusion-bonded metal shims. Producing similar devices from ceramic materials provided unique challenges in shim patterning, bonding, and device integrity during the bonding process.
Commercially available green ceramic tape was used as a starting material for producing ceramic shims. Demon-stration shims were patterned from 250-micron-thick tape using a CO2 laser (Figure 2). A bonding procedure was developed that allowed a monolithic multichannel ceramic component to be bonded to the component with a minimum of distortion. A completed multichannel ceramic test component is shown in Figure 3.
Figure 2. Laser-machined green ceramic tape shims used to
produce a monolithic microchannel ceramic component.
Figure 3. Bonded ceramic test device produced by laminating
patterned green tape shims shown in Figure 2.
Martin PM, DW Matson, and WD Bennett. 1999. "Laminated Plastic Microfluidic Components for Biological and Chemical Systems." Journal of Vacuum Science and Technology A, 17, 2264-2269.
Martin PM, DW Matson, and WD Bennett. 1999. "Microfabrication Methods for Microchannel Reactors and Separations Systems." Chemical Engineering Communications, 173, 245-254.
Martin PM, DW Matson, WD Bennett, DC Stewart, and Y Lin. 1999. "Laser Micromachined and Laminated Microfluidic Components for Miniaturized Thermal, Chemical and Biological Systems." SPIE Conference Proceedings, Vol. 3680. Design, Test, and Micro-fabrication of MEMS and MOEMS, pp. 826-833.
Matson DM, PM Martin, DC Stewart, AY Tonkovich, M White, JL Zilka, and GL Roberts. April 1999. "Fabri-cation of Microchannel Chemical Reactors using a Metal Lamination Process." Proceedings of IMRET3, 3RD International Conference on Microreaction Technology, Frankfurt.
Martin PM, DW Matson, DL Brenchley, MK Drost, and RS Wegeng. 1999. "PNNL Develops MICRO-CATS for DARPA, DOE, and NASA." Invited article in Micromachine Devices 4(8):1-6.
Matson DW, PM Martin, WD Bennett, DC Stewart, and CC Bonham. September 1999. "Laminated Ceramic Components for Micro Fluidic Applications." SPIE Conference Proceeding Vol 3877: Microfluidic Devices and Systems, pp. 95-100, Santa Clara, California.
Matson DW, PM Martin, WD Bennett, DE Kurath, Y Lin, and DJ Hammerstrom. 1998. "Fabrication Processes for Polymer-Based Microfluidic Analytical Devices, pp.371-374." Micro Total Analysis Systems '98, DJ Harrison and A van den Berg, eds. Banff, Alberta.
Matson DW, PM Martin, and WD Bennett. November 1998. "Laser Machined Components for Microanalytical and Chemical Separation Devices." SPIE Conference Proceedings, Vol. 3519, Microrobotics and Micromanipulation, pp. 200-207, Boston.
Matson DW, PM Martin, WD Bennett, DE Kurath, Y Lin, and DJ Hammerstrom. October 1998. "Fabrication Processes for Polymer-Based Microfluidic Analytical Devices." Third International Symposium on Micro Total Analysis Systems, Banff, Alberta.
Matson, DW PM Martin, and WD Bennett. November 1998. "Laser Machined Components for Microanalytical and Chemical Separation Devices." SPIE International Symposium on Intelligent Systems and Advanced Manufacturing, Boston.
Martin PM, DW Matson, WD Bennett, DC Stewart, and Y Lin. March 1999. "Laser Micromachined and Laminated Microfluidic Components for Miniaturized Thermal, Chemical and Biological Systems." SPIE Conference on Micromachining and Microfabrication, Paris.
Matson DM, PM Martin, DC Stewart, AY Tonkovich, M White, JL Zilka, and GL Roberts. April 1999. "Fabrication of Microchannel Chemical Reactors Using a Metal Lamination Process." 3RD International Conference on Microreaction Technology, Frankfurt.
Matson DW, PM Martin, WD Bennett, DC Stewart, and CC Bonham. September 1999. "Laminated Ceramic Components for Micro Fluidic Applications." SPIE 1999 Symposium on Micromachining and Microfabrication, Santa Clara, California.
The authors would like to thank Rick Cameron, Dean Matson, and Don Stewart for designing and fabricating the adsorption device.
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