Characterization and optimization of slanted well designs for microfluidic mixing under electroosmotic flow.

Recently, a series of slanted wells on the floor of a microfluidic channel were experimentally shown to successfully induce off-axis transport and mixing of two confluent streams when operating under electroosmotic (EO) flow. This paper will further explore, through numerical simulations, the parameters that affect off-axis transport under EO flow with an emphasis on optimizing the mixing rate of (a). two confluent streams in steady-state or (b). the transient scenario of two confluent plugs of material, which simulates mixing after an injection. For the steady-state scenario, the degree of mixing was determined to increase by changing any of the following parameters: (1). increasing the well depth, (2). decreasing the well angle relative to the axis of the channel, and (3). increasing the EO mobility of the well walls relative to the mobility of the main channel. Also, it will be shown that folding of the fluid can occur when the well angle is sufficiently reduced and/or when the EO mobility of the wells is increased relative to the channel. The optimum configuration for the transient problem of mixing two confluent plugs includes shallow wells to minimize the well residence time, and an increased EO mobility of the well walls relative to the main channel as well as small well angles to maximize off-axis transport. The final design reported here for the transient study reduces the standard deviation of the concentration across the channel by 72% while only increasing the axial dispersion of the injected plug by 8.6 % when compared to a plug injected into a channel with no wells present. These results indicate that a series of slanted wells on the wall of a microchannel provides a means for controlling and achieving a high degree of off-axis transport and mixing in a passive manner for micro total analysis system (microTAS) devices that are driven by electroosmosis.

[1]  J. Rossier,et al.  UV Laser Machined Polymer Substrates for the Development of Microdiagnostic Systems. , 1997, Analytical chemistry.

[2]  S. Jacobson,et al.  Microchip device for performing enzyme assays. , 1997, Analytical chemistry.

[3]  J. Michael Ramsey,et al.  Dispersion Sources for Compact Geometries on Microchips , 1998 .

[4]  D. J. Harrison,et al.  Microchip systems for immunoassay: an integrated immunoreactor with electrophoretic separation for serum theophylline determination. , 1998, Clinical chemistry.

[5]  J P Landers,et al.  Infrared-mediated thermocycling for ultrafast polymerase chain reaction amplification of DNA. , 1998, Analytical chemistry.

[6]  A. Manz,et al.  Microstructure for efficient continuous flow mixing , 1999 .

[7]  S. Jacobson,et al.  Microfluidic devices for electrokinetically driven parallel and serial mixing , 1999 .

[8]  J Wang,et al.  Micromachined electrophoresis chips with thick-film electrochemical detectors. , 1999, Analytical chemistry.

[9]  R. Mathies,et al.  Radial capillary array electrophoresis microplate and scanner for high-performance nucleic acid analysis. , 1999, Analytical chemistry.

[10]  Andreas Manz,et al.  Chip-based microsystems for genomic and proteomic analysis , 2000 .

[11]  S. Jacobson,et al.  Integrated system for rapid PCR-based DNA analysis in microfluidic devices. , 2000, Analytical chemistry.

[12]  D. Jed Harrison,et al.  Analytical microdevices for mass spectrometry , 2000 .

[13]  S. Quake,et al.  Monolithic microfabricated valves and pumps by multilayer soft lithography. , 2000, Science.

[14]  Handique,et al.  Nanoliter liquid metering in microchannels using hydrophobic patterns , 2000, Analytical chemistry.

[15]  M. Tarlov,et al.  Control of flow direction in microfluidic devices with polyelectrolyte multilayers. , 2000, Analytical chemistry.

[16]  Stephen J. Haswell,et al.  Chemical and biochemical microreactors , 2000 .

[17]  Yolanda Y. Davidson,et al.  Surface modification of poly(methyl methacrylate) used in the fabrication of microanalytical devices. , 2000, Analytical chemistry.

[18]  J Taylor,et al.  Development of a multichannel microfluidic analysis system employing affinity capillary electrophoresis for immunoassay. , 2001, Analytical chemistry.

[19]  C H Mastrangelo,et al.  On-chip thermopneumatic pressure for discrete drop pumping. , 2001, Analytical chemistry.

[20]  C H Mastrangelo,et al.  Monolithic capillary electrophoresis device with integrated fluorescence detector. , 2001, Analytical chemistry.

[21]  M. Gaitan,et al.  Temperature measurement in microfluidic systems using a temperature-dependent fluorescent dye. , 2001, Analytical chemistry.

[22]  Asterios Gavriilidis,et al.  Mixing characteristics of T-type microfluidic mixers , 2001 .

[23]  G. Whitesides,et al.  Generation of Gradients Having Complex Shapes Using Microfluidic Networks , 2001 .

[24]  K. Mogensen,et al.  Monolithic integration of microfluidic channels and optical waveguides in silica on silicon. , 2001, Applied optics.

[25]  F. Regnier,et al.  A picoliter-volume mixer for microfluidic analytical systems. , 2001, Analytical chemistry.

[26]  Timothy J. Johnson,et al.  Chemical mapping of hot-embossed and UV-laser-ablated microchannels in poly(methyl methacrylate) using carboxylate specific fluorescent probes , 2001 .

[27]  I. Mezić,et al.  Chaotic Mixer for Microchannels , 2002, Science.

[28]  L. Locascio,et al.  Control of electroosmotic flow in laser‐ablated and chemically modified hot imprinted poly(ethylene terephthalate glycol) microchannels , 2002, Electrophoresis.

[29]  T. Johnson,et al.  Rapid microfluidic mixing. , 2002, Analytical chemistry.