Computational Prototyping of the Programmable Fluid Processor

Figure 2: Three electrostatic forces contribute to the droplet migration: the DEP in the volume an d droplet surface, the EWOD at the triphase (droplet, suspending liquid, hydrophobic coatin g surface) contact trace. Electro - wetting DEP - field non - uniformity DEP - dielectric discontinuity Electro - wetting DEP - field non - uniformity DEP - dielectric discontinuity Figure 3: Sample simulation visualization. A charged neighboring electrode generates a non-uniform electric field that will induce the droplet to migrate. The droplet surface is colored by the electric potential. (The insulating fluid and th e hydrophobic coating layer are removed for clarity). Computational Prototyping of the Programmable Fluid Processor Jun Zeng and Tom Korsmeyer Coventor, Inc. The Programmable Fluid Processor (PFP), currently under development at M. D. Anderson Cancer Center, will have applications in disease screening, environmental monitoring, and battlefield detection of biochemical agents [1]. In this device, an electrostatic field exerts forces on dielectric droplets suspended in an immiscible insulating liquid medium. This phenomenon is known as dielectrophoresis (DEP). The electrostatic field is generated by an array of electrodes, each of which is addressable so that a droplet, or a group of droplets, can be directed to desired locations, where the droplets can merge, mix, and split. The droplets are used as carriers of different chemical compounds so that a programmed chemical assay can be conducted. Recent advances in semiconductor manufacturing technology have enabled researchers to fabricate such BioChips at the size of less than a centimeter [2]. The design of the PFP and its operating programs calls for a detailed understanding of DEP-driven droplet formation and migration; that is, droplet behavior with a given electrode configuration must be reliably predicted. This demands full-dimensional, transient, simulation capabilities that incorporate electromechanics and multiphase-flow hydrodynamics. The work reported here addresses such a simulation need for the first time. We describe a full-dimensional, transient, electrohydrodynamics, numerical simulation tool based on a proven computational fluid dynamics technique [3]. We present the results of this simulation tool from an investigation of droplet dielectrophoresis in the context of the PFP. These include a study of droplet migration under a non-uniform electric field and a study of the effects on droplet behavior of droplet dimension, electrode dimension, electrode spacing, and dielectric coating. Zeng and Korsmeyer acknowledge the support of The Defense Advanced Research Projects Agency (DARPA) under contract DAAD10-00-1-0515 from the Army Research Office to the University of Texas M.D. Anderson Cancer Center. Contact Author: Jun Zeng, Ph.D., Coventor Inc., 625 Mount Auburn Street, Cambridge, MA 02138 Ph: 617-497-6880 ext. 259 Fax: 617-497-6882 E-mail: jun.zeng@coventor.com Reference [1] J. Vykoukal, J. A. Schwartz, F. F. Becker and P. R. C. Gascoyne, “A Programmable Dielectrophoretic Fluid Processor For Droplet-based Chemistry”, Proceedings of the µTAS 2001 Symposium, Kluwer Academic Publishers, pp. 72-74 [2] P. Krulevitch, “Polymer-based Biomedical Microsystems”, BioMEMS 2002, April 25-26, 2002, Boston, MA [3] C. W. Hirt and B. D. Nichols, 1981, “Volume of Fluid (VOF) Method for the Dynamics of Free Boundaries”, Journal of Computational Physics, Vol. 39, pp. 201-225 Figure 1: Elevation view of the Programmable Fluid Processor. . for clarity). Computational Prototyping of the Programmable Fluid Processor Jun Zeng and Tom Korsmeyer Coventor, Inc. The Programmable Fluid Processor (PFP),. “Volume of Fluid (VOF) Method for the Dynamics of Free Boundaries”, Journal of Computational Physics, Vol. 39, pp. 201-225 Figure 1: Elevation view of the Programmable