| Methods and devices for high-throughput dielectrophoretic concentration -> Monitor Keywords |
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Methods and devices for high-throughput dielectrophoretic concentrationRelated Patent Categories: Liquid Purification Or Separation, Casing Divided By Membrane Into Sections Having Inlet(s) And/or Outlet(s), Planar MembraneMethods and devices for high-throughput dielectrophoretic concentration description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060201868, Methods and devices for high-throughput dielectrophoretic concentration. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention generally relates to dielectrophoresis and its application in analytical devices and filtration technologies. [0004] 2. Description of the Related Art [0005] Dielectrophoresis (DEP) is the motion of particles caused by the effects of conduction and dielectric polarization in non-uniform electric fields. Unlike electrophoresis, where the force acting on a particle is determined by its net charge, the dielectrophoretic force depends on the geometrical, conductive, and dielectric properties of the particle. A complex conductivity of a medium can be defined as .sigma.*=.sigma.+i.omega..epsilon., where .sigma. is the real conductivity and .epsilon. is the permittivity of the medium, i is the square root of -1, and .omega. is the angular frequency of the applied electric field, E. According to well-known theory, the dielectrophoretic force is proportional to the differences in complex conductivity of the particle and suspending liquid and square of the applied electric field. Without being bound by theory, for a spherical particle of radius r, the DEP force, F.sub.DEP is given by F.sub.DEP=2.pi.r.sup.3.epsilon..sub.mRe[f.sub.CM].gradient.E.sup.2 where .epsilon..sub.m is the absolute permittivity of the suspending medium, E is the local (rms) electric field, .gradient. is the del vector operator and Re[f.sub.CM] is the real part of the Clausius-Mossotti factor, defined as: f CM = .sigma. p * - .sigma. m * .sigma. p * + 2 .times. .times. .sigma. m * where .sigma..sub.p* and .sigma..sub.m* are the complex conductivities of the particle and medium respectively, as described in Hughes, et al. (1998) Biochimica et Biophysica Acta 1425:119-126, which is herein incorporated by reference. Depending on the relative conductivities of the particle and medium, the Clausuis-Mossotti factor can be positive, resulting in a force toward stronger electric fields, or negative, resulting in a force away from stronger electric fields. The particle motion toward and away from stronger electric fields is called, respectively, positive and negative DEP. [0006] Thus, when a particle is exposed to a non-uniform electric field, it experiences dielectrophoretic forces resulting from conduction and polarization that scale with the electric field intensity. The magnitude, sign, and phase of these forces depend on the frequency of the applied field and electrical properties of the particle and medium, such as conductivity, permittivity, morphology and shape of the particle. Thus dielectrophoresis can be used to sort and move particles selectively. See Pohl, H. A., J. Appl. Phys., 22:869-871; Pohl, H. A., Dielectrophoresis, Cambridge University Press (1978); Huang Y., R. C. Gascoyne et al., Biophysical Journal, 73:1118-1129; Wang X. B., Gascoyne, R. C., Anal. Chem. 71:911-918, 1999; and U.S. Pat. No. 5,858,192, all of which are hereby incorporated by reference. [0007] Insulator-based (electrodeless) dielectrophoresis (iDEP) has been previously described and utilized for the selective concentration and separation of analytes in microfluidic devices. See Cummings and Singh (2003) Anal. Chem. 75:4724-4731, Lapizco-Encinas, et al. (2004) Electrophoresis 25:1695-1704, and Lapizco-Encinas, et al. (2004) Anal. Chem. 76:1571-1579, which are herein incorporated by reference. These devices use spatially nonuniform insulating structures to generate the nonuniform electric field needed to drive DEP. These iDEP devices are practically limited to processing microliter volumes and require microfabrication. Prior art devices and methods employing iDEP may be used effectively for systems that process such small-volume samples, but are ineffective for real-time monitoring and analysis of large volumes and flows, e.g., flow rates greater than one liter of per hour. [0008] Thus, a need exists for methods and devices that allow dielectrophoretic based assays of large volumes and high flow rates. SUMMARY OF THE INVENTION [0009] The present invention provides a substrate comprising a plurality of pores and a nonuniform electric field having local extrema located near the pores. In some embodiments, the substrate is a membrane, a film, or a filter. In some embodiments, the substrate is a woven structure of a plurality of fibers. In some embodiments, the substrate is a non-woven structure of a plurality of fibers. In some embodiments, the substrate is a plurality of aligned fibers. In some embodiments, the substrate comprises a material with insulative properties. In some embodiments, the substrate comprises a material with conductive properties. [0010] In some embodiments, the present invention provides a method for assaying, inhibiting, or concentrating analytes in a fluid sample which comprises passing the fluid sample through or in the vicinity of a substrate having a plurality of pores and a nonuniform electric field having local extrema located near the pores. In some embodiments, the analytes having a size larger than the pores are physically entrapped on one side of the substrate. In some embodiments, the analytes having a size smaller than the pores pass though the pores of the substrate. In some embodiments, the analytes are immobilized on or constrained in a given area from the surface of the substrate due to dielectrophoretic forces. In some embodiments, the substrate is a membrane, a film, or a filter. In some embodiments, the substrate is a woven structure of a plurality of fibers. In some embodiments, the substrate is a non-woven structure of a plurality of fibers. In some embodiments, the substrate is a plurality of aligned fibers. In some embodiments, the substrate comprises a material with insulative properties. In some embodiments, the substrate comprises a material with conductive properties. [0011] In some embodiments, the present invention provides a device for assaying, inhibiting, or concentrating analytes in a fluid sample which comprises at least one assembly comprising at least one substrate having a plurality of pores capable of a nonuniform electric field gradient having local extrema located near the pores in the presence of an applied field and at least one electrode. In some embodiments, the analytes having a size larger than the pores are physically entrapped on one side of the substrate. In some embodiments, the analytes having a size smaller than the pores pass though the pores of the substrate. In some embodiments, the analytes are immobilized on or constrained in a given area from the surface of the substrate due to dielectrophoretic forces. In some embodiments, the substrate is a membrane, a film, or a filter. In some embodiments, the substrate is a woven structure of a plurality of fibers. In some embodiments, the substrate is a non-woven structure of a plurality of fibers. In some embodiments, the substrate is a plurality of aligned fibers. In some embodiments, the substrate comprises a material with insulative properties. In some embodiments, the substrate comprises a material with conductive properties. In some embodiments, the assembly comprises at least one spacer. In some embodiments, the device comprises two or more assemblies. In some embodiments, the device further comprises at least one component selected from the group consisting of a fluid inlet, a fluid outlet, a substrate housing, a gasket, an insert, a viewing area, a delivery device, a collection device, a spacer, and a valve. In some embodiments, the electrode is a pin electrode or a wire mesh. In some embodiments, the electrode is a remote electrode. In some embodiments, the substrate is transverse to the flow of the fluid sample. In some embodiments, the substrate is substantially normal to substantially aligned with the flow of the fluid sample. In some embodiments, the substrate is about 80 degree incidence to about 10 degree incidence to the flow of the fluid sample. [0012] Both the foregoing general description and the following detailed description are exemplary and explanatory only and are intended to provide further explanation of the invention as claimed. The accompanying drawings are included to provide a further understanding of the invention and are incorporated in and constitute part of this specification, illustrate several embodiments of the invention, and together with the description serve to explain the principles of the invention. DESCRIPTION OF THE DRAWINGS [0013] This invention is further understood by reference to the drawings wherein: [0014] FIG. 1A shows an example of a porous substrate, a phase separated membrane. [0015] FIG. 1B shows an example of a porous substrate, a track etched membrane. [0016] FIG. 2A shows dielectrophoretic depletion wherein the negative DEP of particles is larger than the pore diameter, insulative substrate. [0017] FIG. 2B shows dielectrophoretic depletion wherein DEP of particles is smaller than the pore diameter, insulative substrate. [0018] FIG. 2C shows dielectrophoretic depletion wherein positive DEP of particles is larger than the pore diameter, conductive substrate. [0019] FIG. 2D shows dielectrophoretic depletion wherein positive DEP of particles is smaller than the pore diameter, conductive substrate. [0020] FIG. 3A shows dielectrophoretic enhancement wherein positive DEP of particles is larger than the pore diameter, insulative substrate. [0021] FIG. 3B shows dielectrophoretic enhancement wherein positive DEP of particles is smaller than the pore diameter, insulative substrate. [0022] FIG. 3C shows dielectrophoretic enhancement wherein negative DEP of particles is larger than the pore diameter, conductive substrate. Continue reading about Methods and devices for high-throughput dielectrophoretic concentration... 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