On-chip analysis of particles and fractionation of particle mixtures using light-controlled electrokinetic assembly of particles near surfaces
First Claim
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1. A method of fractionation of a mixture of particles comprising:
- providing a first electrode positioned in the first plane and a second electrode positioned in a second plane different from the first plane, an electrolyte solution located therebetween and a plurality of particles suspended at an interface between the electrolyte solution and the second electrode, wherein the second electrode is a planar light-sensitive electrode having a surface and an interior, the surface or the interior having been patterned to modify the spatial distribution of the interfacial electric field, and wherein the particles comprise at least two types of particles, each particle type having a distinguishable relaxation frequency; and
generating an electric field between the first and the second electrode by applying an AC voltage between the two electrodes, said electric field having a frequency that is less than or equal to the relaxation frequency of at least one of said particle types but greater than the relaxation frequencies of at least one other of said particle types, and also illuminating the interface with a predetermined light pattern, wherein the electric field in combination with the patterning of the electrode and the light pattern produces fractionation of the particles having relaxation frequencies greater than or equal to the frequency of the electric field from other particles.
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Abstract
A method and apparatus for fractionation of a mixture of particles and for particle analysis are provided, in which LEAPS (“Light-controlled Electrokinetic Assembly of Particles near Surfaces”) is used to fractionate and analyze a plurality of particles suspended in an interface between an electrode and an electrolyte solution. A mixture of particles are fractionated according to their relaxation frequencies, which in turn reflect differences in size or surface composition of the particles. Particles may also be analyzed to determine their physical and chemical properties based on particle relaxation frequency and maximal velocity.
88 Citations
30 Claims
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1. A method of fractionation of a mixture of particles comprising:
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providing a first electrode positioned in the first plane and a second electrode positioned in a second plane different from the first plane, an electrolyte solution located therebetween and a plurality of particles suspended at an interface between the electrolyte solution and the second electrode, wherein the second electrode is a planar light-sensitive electrode having a surface and an interior, the surface or the interior having been patterned to modify the spatial distribution of the interfacial electric field, and wherein the particles comprise at least two types of particles, each particle type having a distinguishable relaxation frequency; and
generating an electric field between the first and the second electrode by applying an AC voltage between the two electrodes, said electric field having a frequency that is less than or equal to the relaxation frequency of at least one of said particle types but greater than the relaxation frequencies of at least one other of said particle types, and also illuminating the interface with a predetermined light pattern, wherein the electric field in combination with the patterning of the electrode and the light pattern produces fractionation of the particles having relaxation frequencies greater than or equal to the frequency of the electric field from other particles. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
an illumination source;
a reconfigurable mask composed of an array of pixels, said pixels being actively controllable and directly addressable by means of a computer-controlled circuit and computer interface, said computer-controlled circuit being operated using a software program providing temporal control of the intensity of illumination emanating from each pixel so as to form the illumination pattern comprising the predetermined arrangement of light and dark zones;
a projection system suitable for imaging the reconfigurable mask onto the substrate; and
an imaging system incorporating a camera capable of viewing said substrate with superimposed illumination pattern.
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14. A method of determining the zeta potential of particles suspended in an electrolyte solution and/or the mobility of ions or molecules within a region adjacent to said particles, the method comprising:
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providing a plurality of particles having a characteristic relaxation frequency suspended at an interface between an electrolyte solution which resides in a gap between a first electrode and a light-sensitive electrode;
illuminating the interface with a predetermined light pattern;
generating an electric field at the interface by application of an AC voltage, said electric field having a frequency, and adjusting the frequency of said electric field to produce formation of a planar array of substantially one layer of particles in a designated area on the electrode defined by the pattern of illumination, wherein said interface exhibits impedance gradients when subjected to the electric field and the illumination;
determining the relaxation frequency of said particles;
determining maximal velocity (vmax) of said particles; and
converting the maximal velocity and the relaxation frequency to either the zeta potential or the surface conductivity of said particles, or to both the zeta potential and the surface conductivity. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22)
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23. A method of determining the zeta potential of particles suspended within an electrolyte solution and/or the mobility of ions or molecules within a region adjacent to said particles, the method comprising:
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providing a first electrode positioned in the first plane and a second electrode positioned in a second plane different from the first plane, an electrolyte solution located therebetween and a plurality of particles of one or more types, each type having a characteristic relaxation frequency, said particles being suspended at an interface between the electrolyte solution and the second electrode, wherein the second electrode comprises a planar electrode having a surface and an interior, the surface or the interior having been patterned to modify the spatial distribution of the interfacial electric field;
generating an electric field between the first and the second electrode by applying an AC voltage between the two electrodes, said electric field having a frequency;
adjusting the frequency of said electric field to produce particle transport into a designated area of the electrode defined by said patterning of the electrode;
determining relaxation frequencies of said one or more types of particles;
determining maximal velocity (vmax) of transport of said particles through image analysis and particle tracking; and
converting said relaxation frequency and said maximal velocity to either the zeta potential of said particles or the mobility of ions or molecules within a region adjacent to said particles, or to both the zeta potential and said mobility. - View Dependent Claims (24, 25, 26, 27, 28, 29, 30)
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Specification