Microfluidic Devices for Electrokinetically Driven Parallel and Serial Mixing

Abstract

Microfabricated devices for parallel and serial mixing of fluids are demonstrated. To simplify the voltage control hardware, electrokinetic mixing is effected using a single voltage source with the channels dimensioned to perform the desired voltage division. In addition, the number of fluid reservoirs is reduced by terminating multiple buffer, sample, or analysis channels in single reservoirs. The parallel mixing device is designed with a series of independent T-intersections, and the serial mixing device is based on an array of cross intersections and sample shunting. These devices were tested by mixing a sample with buffer in a dilution experiment. Sample fractions of 1.0, 0.84, 0.67, 0.51, 0.36, 0.19, and 0 were generated for the parallel mixing device, and sample fractions of 1.0, 0.36, 0.21, 0.12, and 0.06 for the serial mixing device.Microfabricated devices for performing chemical and biochemical assays have garnered increased attention over the last several years. 1-3 Considerable effort has been dedicated to developing functional elements to be incorporated into these labon-a-chip devices. A key issue is sample and reagent mixing. With electrokinetic material transport, reagents are mixed in proportions dictated by the applied potentials, the geometry of the channels, and the properties of the materials in those channels. To date, the proportioning of two or more fluids in different ratios has been accomplished by controlling the electric potentials applied to the fluidic reservoirs to effect dilution, 4 reactions, 5,6 and solvent programming. 7,8 These have required voltage control external to the microchip, e.g., programmable power supplies.Some simple integrated devices have combined precolumn 9 and postcolumn 10-12 derivatization reactions in conjunction with electrophoretic separations. In addition, restriction digestions 13 and competitive immunoassays 14 have been coupled to product analysis downstream. More features being integrated into a planar format have led to studying compact microchip designs, 15 fabricating arrays of channels for DNA analysis, 16,17 and multiple sample PCR with product analysis. 18 Coupled to this increased integration is the added complexity of the hardware needed to control microfluidic operations. One approach to simplify the control hardware for electrokinetic manipulations is to design the fluidic channels to perform the appropriate voltage division for reagent mixing and reactions.In this paper, we describe microfluidic designs that simplify the voltage control necessary to effect parallel and serial electrokinetic mixing on microchips. If the fluidic channels provide the appropriate voltage division, only a single fixed voltage source is required to transport and mix material. This minimizes the highvoltage hardware necessary to operate the microfluidic chip. In an effort to make the microchip architecture compact, multiple buffer, sample, or analysis channels terminate in single reservoirs. To test the parallel and serial mixing schemes, a sample was diluted with ...

Micro reactors: principles and applications in organic synthesis

“…Elegant designs of networks containing cascades of T-junctions connected by suitably long, tortuous channels have been used to produce output channels giving simultaneously a series of fully-mixed dilutions of the original input solution. 48,49 This type of multiple output is useful when using a micro reactor to determine, for example, a calibration plot of detector signal versus the concentration of an analyte species. The fact that the laminar¯ows of reagent streams inter-diffuse only relatively slowly has been exploited by using chemically-reactive reagent streams.…”

Peer Reviewed: Microfluidics: Controlling Fluids in Small Places

“…Understanding these fluid manipulations is important for onchip serial dilutions or derivatization reactions, which can be done, in their simplest forms, by varying the applied potentials to the analyte and buffer reservoirs and allowing diffusive transport (51). More elegant and complex designs involving both serial and parallel dilutions have higher throughput and faster interaction times (Figure 4) (52). These techniques are important for both precolumn and postcolumn reactions.…”

Thermal mixing of two miscible fluids in a T-shaped microchannel

“…Bokenkamp et al 7 achieved better mixing efficiency by connecting two T-shaped micromixers with a commercially available quench-flow instrument. Jacobson et al 8 fabricated devices for parallel mixing, which consists of a series of independent T-shaped intersections. Gobby et al 9 studied the mixing characteristics of gaseous flow in a T-shaped micromixer by using numerical simulation.…”