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Richard Oleschuk

 
  Microfludic Devices

 
  Contact Information:  
  Professor of Chemistry
B.Sc., 1994, Ph.D., 1998, University of Manitoba
Post Doctoral Fellow 1998-2000, University of Alberta

Tel: (613) 533-6000 x36704
e-mail: oleschuk@chem.queensu.ca


 
  Development of Microfluidic Devices

Recent developments in the area of micro-Total Analysis Systems (ยต-TAS) have included systems that perform chemical reactions, separation and detection on a single microchip. Photolithography and chemical etching techniques are utilized to fabricate three dimensional microfluidic structures that can be used to develop miniaturized analysis systems. Compared to conventional systems, microfluidic devices use smaller amounts of samples and provide shorter analysis times, due to their small dimensions. In fact complex separations can be conducted in only seconds using less than one hundred picoliters of sample! Typically microfluidic devices have been constructed within glass because of the ease of fabrication and utility of electrokinetic pumping. However glass devices are relatively expensive to manufacture precluding their utilization in single use applications such as biomedical analysis and genetic testing. place here Polymer materials offer an alternative to expensive glass devices and can be tailor made for a specific application. In the last two years, researchers have begun to realize the advantages of polymer devices. Methods including casting, hot embossing and injection molding have been used to fabricate plastic devices with sufficient detail and resolution to be utilized as microfluidic devices. Most efforts to date have focused place here

Polydimethylsiloxane on using polydimethyl siloxane (PDMS) as the substrate material. Although PDMS is relatively easy to use, it is more hydrophobic than glass, making it more difficult to wet with aqueous solvents. Different polymers and methods of device fabrication are utilized by our research group to develop novel microfluidic devices within plastics. Simple devices are prepared from a silicon mold shown below. Mold construction involves the use of a CAD (computer assisted drawing) program to generate a photo-mask. Photolithography combined with wet etching is then utilized to yield a silicon mold. The device is molded by pouring the polymer material onto the silicon mold, followed by curing at an elevated temperature. The device is removed from the mold and fitted with a cover plate having pre-punched access holes. Polymer properties essential to the performance of microfluidic devices are explored including: wetting ability, reproducibility, aging characteristics, sample/ buffer compatibility, surface/ sample adsorption and separation performance. place here

Polyurethanes and epoxy resins are large groups of block co-polymers with a wide variety of structures and chemistries that can be tailor made with surface properties to suit a particular application. One problem that has arisen using PDMS as a substrate material is the lack of charge on the surface of the polymer. Without sufficient surface charge EOF can not be generated preventing fluid control within the devices. Where a device with a highly charged/hydrophilic surface similar to glass is required polyurethanes with siloxane segments can be utilized. For applications such as protein and DNA analysis where a hydrophobic surface relatively devoid of charge is needed polyurethanes with hydrophobic polytetramethylene oxide segments can be used. Due to the large numbers of applications that both polyurethanes and epoxy resins are used in materials that have the desired surface properties are commercially available or can be easily fabricated. The effect of different polymer chemistries and additives to modify the channel wall for different pH ranges would be explored. An important application would be the use of polymers in the low pH range where glass devices do not yield sufficient electroosmotic flow because the silanol groups at the surface of the glass are no longer charged. When using glass devices substantial EOF is generated only above pH 4-5. Using polymers with functional groups that ionize below this pH would extend the analysis range to include low pH's. Ultimately different polymer devices constructed will be coupled with electrospray mass spectrometry for DNA and proteomic applications. and investigating the compatibility of plastics with different sample and solvent types. place here Electrospray ionization has become one of the most versatile ionization methods for mass spectrometry. Liquid, under the influence of a high electric field is sprayed into a mass spectrometer where the mass to charge ratio of the analyte is determined. Place here

The relatively soft ionization technique can be utilized to measure a large range of molecules (several hundred to several thousand molecular weight) including proteins and peptides, yielding both molecular weight and structural information. Integration of all aspects of protein sample handling within a microchip device is a clear goal for microfluidics. Such integration will enable faster, more reproducible and more highly automated sample preparation for introduction into the mass spectrometer helping eliminate the analysis bottle neck facing drug discovery and Proteomics research fields. and investigating the compatibility of plastics with different sample and solvent types.



 
  Publications:  
  R. D. Oleschuk, D. J. Harrison, Analytical Microdevices for Mass Spectrometry, (Review), Trends in Analytical Chemistry (TRAC), 19 (2000) 379

R. D. Oleschuk, M. E. McComb, M. King, Y. Marois, A. Chow, K. G. Standing, H. Perreault, The Use of MALDI-MS for the Analysis of Proteins Adsorbed onto Biomaterials, Biomaterials, August 2000.

R. D. Oleschuk, L. L. Shultz-Lockyear, D. J. Harrison, Trapping of Bead Based Reagents Within Microfluidic Systems: On-chip Solid Phase Extraction and Electrochromatography , Anal. Chem. 72 (2000) 585.

G. Ocvirk, M. Munroe, T. Tang, R. D. Oleschuk, K. Westra, D. J. Harrison; Electrokineticcontrol of fluid flow in native poly(dimethylsiloxane) capillary electrophoresis devices, Electrophoresis, 21 (2000) 107.

S. Shojania, M. E. McComb, R. D. Oleschuk, H. Perreault, H. D. Gesser, A. Chow, Qualitative Analysis of Complex Mixtures of VOC's Using the Inside Needle Capillary Adsorption Trap, Can. J. Chem. 77 (1999) 1716-1727

D. J. Harrison, R. D. Oleschuk, L. L. Shultz-Lockyear , C. Skinner , P. Li, U.S. Patent Application 09/450272 Apparatus and Method for Trapping Bead Based Reagents Within Microfluidic Systems, April 2000.

M. E. McComb, R. D. Oleschuk, A. Chow, W. Ens, K. G. Standing, M. Smith, H. Perreault, Matrix Assisted Laser Desorption Ionization Time-of-Flight Mass Spectrometry Analysis of Hemoglobin Variants using Non-Porous Polyurethane Membrane as a Sample Support, Anal.Chem., 70 (1998) 5142.

R. D. Oleschuk and A. Chow, Separation of Platinum and Palladium Using an Organic Impregnated Membrane, Talanta, 45 (1998) 1235-1245.

M. E. McComb, R. D. Oleschuk, D. M. Manley, L. Donald, A. Chow, J. O'Neil, W. Ens, K. G. Standing and H. Perreault, Convenient MALDI-TOFMS of Proteins and Peptides Using a Non-Porous Polyurethane Membrane as a Sample Support, Rapid Comm. in Mass Spectrom., 11 (1997) 1716-1722.

M. E. McComb, R. D. Oleschuk, D. M. Manley, L. Donald, H. Duckworth, A. Chow, J. D. O'Neil, W. Ens, K. G. Standing, H. Perreault, Use of Polyurethane for MALDI-TOFMS Analysis of Whole Blood, Canadian Patent Application, January 30/98, #2,228,413. US Provisional Patent, February 2/98, #073,364.

R. D. Oleschuk and A. Chow, The Separation and Isolation of Gold by Selective Extraction and Transport Through a Polyurethane Ether-Type Membrane, Talanta, 43 (1996) 1545-1554.

R. D. Oleschuk and A. Chow, Transport of Iron Halides Through Polyurethane Ether-Type Membranes, Talanta, 42 (1995) 957-965.