Micromachining technology was used to prepare chemical analysis systems on glass chips (1 centimeter by 2 centimeters or larger) that utilize electroosmotic pumping to drive fluid flow and electrophoretic separation to distinguish sample components. Capillaries 1 to 10 centimeters long etched in the glass (cross section, 10 micrometers by 30 micrometers) allow for capillary electrophoresis-based separations of amino acids with up to 75,000 theoretical plates in about 15 seconds, and separations of about 600 plates can be effected within 4 seconds. Sample treatment steps within a manifold of intersecting capillaries were demonstrated for a simple sample dilution process. Manipulation of the applied voltages controlled the directions of fluid flow within the manifold. The principles demonstrated in this study can be used to develop a miniaturized system for sample handling and separation with no moving parts.

Micromachining a miniaturized capillary electrophoresis-based chemical analysis system on a chip

In this review we discuss the state of the art of the optical whole-field velocity measurement technique micro-scale Particle Image Velocimetry (µPIV). µPIV is a useful tool for fundamental research of microfluidics as well as for the detailed characterization and optimization of microfluidic applications in life science, lab-on-a-chip, biomedical research, micro chemical engineering, analytical chemistry and other related fields of research. An in depth description of the µPIV method is presented and compared to other flow visualization and measurement methods. An overview of the most relevant applications is given on the topics of near-wall flow, electrokinetic flow, biological flow, mixing, two-phase flow, turbulence transition and complex fluid dynamic problems. Current trends and applications are critically reviewed. Guidelines for the implementation and application are also discussed.

Micro-Particle Image Velocimetry (microPIV): recent developments, applications, and guidelines.

Analysis of electroosmotic flow of power-law fluids in a slit microchannel

Characterization of liquid flows in microfluidic systems

Electrophoretic separations on microfluidic chips

Joule heating effect on electroosmotic flow and mass species transport in a microcapillary

A miniature rotating gyroscope is described, in which a 0.5 mm aluminium rotor is levitated, rotated, and constrained by a combination of electromagnetic induction and electrostatic forces generated from a unique planar coil design. Integrated into the planar coil design are the sense electrodes that allow the angular-rate of the device to be measured about two orthogonal axes, and acceleration along the third, producing a multimode inertial sensor. In this paper, the results of electrostatic, rotation, and thermal measurements, together with the finite element and analytical modelling are presented. Excellent agreement is found between the electromagnetic and electrostatic experimental measurements and modelling. A simple viscous drag model is proposed to explain the experimental rotational measurements and its limitations are discussed.

Development of a levitated micromotor for application as a gyroscope

Joule heating is inevitable when an electric field is applied across a conducting medium. It would impose limitations on the performance of electrokinetic microfluidic devices. This article presents a 3-D mathematical model for Joule heating and its effects on the EOF and electrophoretic transport of solutes in microfluidic channels. The governing equations were numerically solved using the finite-volume method. Experiments were carried out to investigate the Joule heating associated phenomena and to verify the numerical models. A rhodamine B-based thermometry technique was employed to measure the solution temperature distributions in microfluidic channels. The microparticle image velocimetry technique was used to measure the velocity profiles of EOF under the influence of Joule heating. The numerical solutions were compared with experimental results, and reasonable agreement was found. It is found that with the presence of Joule heating, the EOF velocity deviates from its normal "plug-like" profile. The numerical simulations show that Joule heating not only accelerates the sample transport but also distorts the shape of the sample band.

Assessment of Joule heating and its effects on electroosmotic flow and electrophoretic transport of solutes in microfluidic channels.

Numerical analysis of the thermal effect on electroosmotic flow and electrokinetic mass transport in microchannels

Joule heating is present in electrokinetic transport phenomena, which are widely used in microfluidic systems. In this paper, a rigorous mathematical model is developed to describe the Joule heating and its effects on electroosmotic flow and mass species transport in microchannels. The proposed model includes the Poisson equation, the modified Navier−Stokes equation, and the conjugate energy equation (for the liquid solution and the capillary wall). Specifically, the ionic concentration distributions are modeled using (i) the general Nernst−Planck equation and (ii) the simple Boltzmann distribution. The relevant governing equations are coupled through the temperature-dependent solution dielectric constant, viscosity, and thermal conductivity, and, hence, they are numerically solved using a finite-volume-based CFD technique. The applicability of the Nernst−Planck equation and the Boltzmann distribution in the electroosmotic flow with Joule heating has been discussed. The results of the time and spatial dev...

Modeling of Electroosmotic Flow and Capillary Electrophoresis with the Joule Heating Effect: The Nernst−Planck Equation versus the Boltzmann Distribution

H. Q. Gong

Papers

Joule heating effect on electroosmotic flow and mass species transport in a microcapillary

Development of a levitated micromotor for application as a gyroscope

Assessment of Joule heating and its effects on electroosmotic flow and electrophoretic transport of solutes in microfluidic channels.

Numerical analysis of the thermal effect on electroosmotic flow and electrokinetic mass transport in microchannels

Modeling of Electroosmotic Flow and Capillary Electrophoresis with the Joule Heating Effect: The Nernst−Planck Equation versus the Boltzmann Distribution