Abstract: Electrostatic capacitance measurements are used to detect chemical or biological analytes, or chemical interactions, with great sensitivity. A diaphragm is coated with a material capable of selectively interacting with an analyte of interest, and interaction of the analyte with the coating exerts stresses tangential to the diaphragm's surface. These stresses cause diaphragm displacements that are sensed as varying capacitance.

Abstract: The disclosure provides methods for the determination of the enantiomeric excess of chiral compounds. The methods involve doping a chiral analyte into an achiral liquid crystal host to form a chiral dopant/host liquid crystal mixture. An electro-optic signature of the mixture is then determined and is used to calculate the enantiomeric excess of the chiral analyte. The disclosure also provides systems for performing the disclosed methods of determining enantiomeric excess.

Abstract: Superparamagnetic (“SPM”) subunits of 1–30 nm average mean diameter (e.g. ferro fluid) subparticles are treated with a magnetically noninterfering substance capable of coating and covering them (e.g, BSA) and they spontaneously form agglomerates of about 100 nm to about 450 nm or higher average mean diameter and are then used to form complexes with target biological ligands such as viruses, contained in large volumes of liquid. The complexes are subjected to the gradient intensity of a strong magnetic field, and excess liquid is removed, where upon an immunochromatographic assay is conducted to determine the identity and/or amount of target ligand present, in which operation SPM particles that bonded to the ligand function as tags for ligand detection.

Abstract: The present invention concerns a novel means by which specific chosen reactions can be accelerated through the use of a new type of artificial enzyme. The invention allows specific reactions to occur at an accelerated rate, even in the presence of other non-chosen molecules, which may be very similar in structure to the chosen reactant. The reactions may be stoichiometric or catalytic.

Abstract: The present invention concerns a novel means by which chemical preparations can be made. Reactions can be accelerated on special chips using microwave energy. The chips contain materials that efficiently absorb microwave energy causing chemical reaction rate increases. The invention is important in many small scale chemical transformations including those used in protein chemistry and in combinatorial chemistry.

Abstract: In a method for analysis biomolecules (3) attached to a solid surface of a substrate (1) are used for detecting the presence of analytes (4) in a sample by binding of the analytes to the biomolecules. The biomolecules (3) are attached directly to the surface of the substrate together with biomolecule-repellent molecules (5), which cover the surface between the biomolecules (3) to prevent nonspecific binding of analytes (4) and other biomolecules. The invention relates also to a biosensor where biomolecules (3) are attached directly to the substrate (1) together with biomolecule-repellent molecules (5), which cover the surface between the biomolecules (3) to prevent non-specific binding of analytes (4) and other biomolecules. The biomolecules (5) can be self-assembled hydrophilic polymers. One example of using the invention is immunological analysis using surface plasmon resonance (SPR).

Abstract: An electronic sensor is provided for detecting the presence of one or more analytes of interest in a sample. The sensor preferably comprises a field effect transistor in which conductance is enhanced by analyte binding to receptors in the active region. An array of sensors may be formed to analyze a sample for multiple analytes.

Abstract: A membrane-based assay device for detecting the presence or quantity of an analyte residing in a test sample is provided. The device utilizes a self-calibrated magnetic binding assay format (e.g., sandwich, competitive, etc.) that includes detection probes capable of generating a detection signal (e.g., fluorescent non-magnetic particles) and calibration probes capable of generating a calibration signal (e.g., fluorescent magnetic particles). The amount of the analyte within the test sample is proportional (e.g., directly or inversely) to the intensity of the detection signal calibrated by the intensity of the calibration signal. It has been discovered that the fluidics-based device of the present invention provides an accurate, inexpensive, and readily controllable method of determining the presence of an analyte in a test sample.

Abstract: The present invention provides an integrated circuit and a method for noise removal in a magnetic nano-particle sensor device. The method of the present invention comprises the steps of sending a conductor current through a conductor to generate a first horizontal magnetic field component at the location of a magneto-resistive sensor. In a further step the optimal operation point of the magneto-resistive sensor is determined by minimizing the noise at the output of the magneto-resistive sensor by means of a noise optimization circuit. By applying an external magnetic field such that nano-particles in the vicinity of the sensor are vertically magnetized, a second horizontal magnetic field component is generated at the location of the sensor. Then, the conductor current is adjusted such that the first horizontal magnetic field component compensates for the second horizontal magnetic field component.

Abstract: Electrodes and configurations for electrochemical bioreactor systems that can use electrical energy as a source of reducing power in fermentation or enzymatic reactions and that can use electron mediators and a biocatalyst, such as cells or enzymes, to produce electricity are disclosed. Example electrodes in the system may comprise: (1) neutral red covalently bound to graphite felt (FIG. 1); (2) a carboxylated cellulose bound to the graphite fell, neutral red bound to the carboxylated cellulose, NAD+ to the graphite fell, and an oxidoreductase (e.g., fumarate reductase) bound to the graphite fell; or (3) a metal ion electron mediator bound to graphite. Various biocatalysts, such as an oxidoreductase, cells of Actinobacillus succinogenes, cells of Escherichia coli, and sewage sludge, are suitable for use in the electrochemical bioreactor system.

Abstract: Disclosed is a sensor for sensing the presence of an analyte component without relying on redox mediators. This sensor includes (a) a plurality of conductive polymer strands each having at least a first end and a second end and each aligned in a substantially common orientation; (b) a plurality of molecular recognition headgroups having an affinity for the analyte component and being attached to the first ends of the conductive polymer strands; and (c) an electrode substrate attached to the conductive polymer strands at the second ends. The electrode substrate is capable of reporting to an electronic circuit reception of mobile charge carriers (electrons or holes) from the conductive polymer strands. The electrode substrate may be a photovoltaic diode.

Abstract: The present invention provides a sensor surface comprising: a substrate coated with a free electron metal; and a matrix layer disposed on the free electron metal, wherein the matrix layer comprises an organic compound having a boronic acid complexing moiety. The matrix is preferably a self-assembled monolayer (SAM), a mixed self-assembled monolayer (mSAM), or combinations thereof.

Abstract: A sensor is provided for detecting a target substance in a sample by detecting a product formed in the presence of an enzyme and an enzyme substrate. The sensor comprises two or more working electrodes, a first capturing molecule immobilized on the working electrodes, and a current-detector for detecting a current value flowing through at least one of the working electrodes. The sensor also comprises a target substance detection means having an arithmetic unit for determining an amount of the target substance in the sample on the basis of the current value detected by the current-detector in a specified period of time, and a crosstalk detecting electrode arranged between the working electrodes for detecting a crosstalk between the working electrodes. The specified period of time is a time necessary for the current value through the crosstalk detecting electrode to show a particular change.

Abstract: The present invention provides a method for detecting an analyte, comprising providing a sensor comprising a substrate coated with a free electron metal, a matrix layer disposed on the free electron metal, the matrix layer comprising an organic compound, wherein the organic compound has a boronic acid complexing moiety and, a boronic acid moiety complexed to the boronic acid complexing moiety; and contacting the sensor with the analyte to elicit a response; and measuring the response thereby detecting the analyte.

Abstract: Method and apparatus for manipulating and monitoring analyte flowing in fluid streams. A giant magnetoresistive sensor has an array of sensing elements that produce electrical output signals which vary in dependence on changes in the magnetic field proximate the sensing elements. The analyte is included in a stream, such that the stream has a magnetic property which is dependent on the concentration and distribution on the analyte therein. The stream is flowed past the giant magnetoresistive sensor and in sufficiently close proximity to cause the magnetic properties of the stream to produce electrical output signals. The electrical output signals are monitored as an indicator of analyte concentration or distribution in the stream flowing past the GMR sensor. Changes in the magnetic field produced by the background stream are introduced by analyte molecules, whose presence in the flow past the GMR will effect the output reading.

Abstract: An improved method for separating materials is provided, using colloidal, magnetizable aggregates, optionally silanized, and coated with a one or more layers of novel polysaccharide derivatives. Materials separated by the aggregates of the invention include inorganic and organic molecules, viruses, organelles, and cells. The invention also relates to a kit for separating such materials. The separated materials are useful in analytical and preparative or in diagnostic and therapeutic techniques.

Abstract: An electrochemical test device is provided for determining the presence or concentration of an analyte in an aqueous fluid sample. The electrochemical test device includes a working electrode and a counter electrode made of an amorphous semiconductor material. The working electrode is overlaid with a reagent capable of reacting with an analyte to produce a measurable change in potential which can be correlated to the concentration of the analyte in the fluid sample. The test device optionally contains a reference electrode made of an amorphous semiconductor material having a reference material on the reference electrode. The test device electrodes can be constructed on a flexible film substrate, such as a polymeric film or a metal foil coated with a non-conductive coating.

Abstract: A method and sensor are provided for detecting the binding of a probe and a target biomolecule by measuring a difference in the shear stress on the surface of the sensor before and after hybridization of the target molecule to the probe, such as nucleic acids or proteins. The shear stress may be measured sensitively and conveniently as an electrical signal without additional fluorescent labeling and without use of expensive additional devices.

Abstract: An apparatus to measure micro-forces includes a cantilever palette with a set of cantilever array blocks. Each cantilever array block includes a set of cantilevers, with each cantilever including a set of cantilever fingers surrounded by a frame with frame fingers. The cantilever fingers and the frame fingers form a diffraction grating. Each cantilever array block is configured to be responsive to a predetermined micro-force, such that cantilevers of the cantilever array block deflect in the presence of the predetermined micro-force, which causes the diffraction grating to diffract light and thereby provide a visual indication of the presence of the predetermined micro-force.

Abstract: A coplanar waveguide biosensor and methods of use include a coplanar waveguide transmission line and a sample containment structure. The coplanar waveguide transmission line is operable to support the propagation of an electromagnetic signal and includes a signal line and one or more spaced apart ground elements. The signal line is configured to conduct a time-varying voltage, and the one or more ground elements are configured to maintain a time-invariant voltage, a detection region being formed between a portion of the signal line and a portion of at least one of the one or more ground elements. Detection methods are improved through the enhancement of the electric field in the detection region via impedance discontinuities in the signal line and ground elements. The sample containment structure intersects the detection region of the coplanar waveguide transmission line and includes a cavity configured to hold 1 ml or less of sample solution within the detection region.

Abstract: A method and apparatus for the manipulation of colloidal particulates and biomolecules at the interface between an insulating electrode such as silicon oxide and an electrolyte solution. Light-controlled electrokinetic assembly of particles near surfaces relies on the combination of three functional elements: the AC electric field-induced assembly of planar aggregates; the patterning of the electrolyte/silicon oxide/silicon interface to exert spatial control over the assembly process; and the real-time control of the assembly process via external illumination. The present invention provides a set of fundamental operations enabling interactive control over the creation and placement of planar arrays of several types of particles and biomolecules and the manipulation of array shape and size. The present invention enables sample preparation and handling for diagnostic assays and biochemical analysis in an array format, and the functional integration of these operations.

Abstract: Novel bipyridyl-osmium complex conjugates and their use in electrochemical assays are described. The redox reversible-osmium complexes can be prepared to exhibit unique reversible redox potentials and can thus be used in combination with other electroactive redox reversible species having redox potentials differing by at least 50 millivolts in electrochemical assays designed for use of multiple electroactive species in the same cell and in the same sample without interference between the two or more redox coupled conjugate systems.

Abstract: The present invention provides novel microfluidic devices and methods that are useful for performing high-throughput screening assays. In particular, the devices and methods of the invention are useful in screening large numbers of different compounds for their effects on a variety of chemical, and preferably, biochemical systems.

Abstract: Superparamagnetic (“SPM”) subunits of 1–30 nm average mean diameter (e.g. ferro fluid) subparticles are treated with a magnetically noninterfering substance capable of coating and covering them (e.g, BSA) and they spontaneously form agglomerates of about 100 nm to about 450 nm or higher average mean diameter and are then used to form complexes with target biological ligands such as viruses, contained in large volumes of liquid. The complexes are subjected to the gradient intensity of a strong magnetic field, and excess liquid is removed, where upon an immunochromatographic assay is conducted to determine the identity and/or amount of target ligand present, in which operation SPM particles that bonded to the ligand function as tags for ligand detection.

Abstract: Disclosed are devices for detecting the presence of a preselected analyte in a fluid sample. The devices comprise a substrate microfabricated to define a sample inlet port, and a mesoscale flow system that includes a sample flow channel extending from the inlet port. The mesoscale flow system further includes an analyte detection region in fluid communication with the flow channel comprised of a binding moiety for specifically binding the analyte. The detection region is constructed with a mesoscale dimension sufficiently small to enhance binding of the binding moiety and the analyte. The binding moiety may be immobilized in the detection region. The mesoscale detection systems of the invention may be used in a wide range of applications, including the detection of cells or macromolecules, or for monitoring reactions or cell culture growth.

Abstract: The subject invention provides new materials and methods for the efficient isolation and purification of stem cells. Specifically, conductive immunopolymers with stem cell specific antibodies can be used to remove stem cells from biological fluids.

Abstract: Disclosed are devices for detecting the presence of a preselected analyte in a fluid sample. The devices comprise a substrate microfabricated to define a sample inlet port, and a mesoscale flow system that includes a sample flow channel extending from the inlet port. The mesoscale flow system further includes an analyte detection region in fluid communication with the flow channel comprised of a binding moiety for specifically binding the analyte. The detection region is constructed with a mesoscale dimension sufficiently small to enhance binding of the binding moiety and the analyte. The binding moiety may be immobilized in the detection region. The mesoscale detection systems of the invention may be used in a wide range of applications, including the detection of cells or macromolecules, or for monitoring reactions or cell culture growth.

Abstract: Novel magnetic assay methods and systems. According to a preferred embodiment, a chromatographic medium, which preferably comprises a test strip, is provided that is designed to be contacted with a test solution having activated magnetic particles such that the solution flows bilaterally thereacross. A magnetic field, generated by a magnet or electromagnet, is selectively applied to the medium which causes the charged particles to become substantially bound at a site on the medium specified by the position of the magnet, to thus form a captured line or zone. In one preferred embodiment, the magnetic field is applied at the site on the medium at which the test solution is contacted. The degree of magnetic force applied to the membrane may be selectively adjusted to vary the width or surface area of the capture line or zone.

Abstract: Disclosed is a sensor for sensing the presence of an analyte component without relying on redox mediators. This sensor includes (a) a plurality of conductive polymer strands each having at least a first end and a second end and each aligned in a substantially common orientation; (b) a plurality of molecular recognition headgroups having an affinity for the analyte component and being attached to the first ends of the conductive polymer strands; and (c) an electrode substrate attached to the conductive polymer strands at the second ends. The electrode substrate is capable of reporting to an electronic circuit reception of mobile charge carriers (electrons or holes) from the conductive polymer strands. The electrode substrate may be a photovoltaic diode.

Abstract: The invention relates to a new process for detecting analytes or binding reactions using measurement of the double refraction, as well as the use of the compounds in analytical chemistry that are necessary for this purpose.

Abstract: A sensor is provided including a polymer capable of having an alterable measurable property from the group of luminescence and electrical conductivity, the polymer having an intermediate combination of a recognition element, a tethering element and a property-altering element bound thereto and capable of altering the measurable property, the intermediate combination adapted for subsequent separation from the polymer upon exposure to an agent having an affinity for binding to the recognition element whereupon the separation of the intermediate combination from the polymer results in a detectable change in the alterable measurable property, and, detecting said detectable change in the alterable measurable property.

Abstract: The present invention relates, in general, to biosensors and, in particular, to bioelectronic sensors comprising a macromolecule immobilized on an electrode surface so that a redox cofactor that is site-specifically attached to the surface of the macromolecule is between the macromolecule and electrode surface ligand-mediated conformational changes alter the geometry of interaction between the redox cofactor and the electrode surface resulting in a change in electronic coupling between the cofactor and electrode.

Abstract: This invention relates to an improved method and system for sensing of one or more analytes. A host molecule, which serves as an adapter/carrier, is used to facilitate interaction between the analyte and the sensor element. A detectable signal is produced reflecting the identity and concentration of analyte present.

Abstract: An integrated optical chip device for molecular diagnostics comprising a tunable laser cavity sensor chip using heterodyned detection at the juncture of a sensor laser and a reference laser, and including a microfluid chip to which the sensor chip is flip-chip bonded to form a sample chamber that includes exposed evanescent field material of the tunable laser cavity to which fluid to be diagnosed is directed.

Abstract: A method of measuring the physical and chemical properties of tissue or cells and a device for the same is provided, with which the physical and chemical environment of the tissue or cells can be changed arbitrarily corresponding to experimental necessities. The device comprises a system 40 for keeping the physical and chemical environment surrounding the biological tissue or cells constant, a system 50 for arbitrarily changing the physical and chemical environment, observation systems 10 and 20 for observing the physical and chemical properties of the tissue or cells, and a system 30 for comparing the change of the physical and chemical properties of the tissue or cells before and after changing the physical and chemical environment. The observation system 10 is a potential measurement device for measuring the electrophysiological properties of the tissue or cells.

Abstract: The invention provides compositions and kits for performing a binding assay for an analyte of interest present in a sample based upon electrochemiluminescence. The compositions and kits comprise an electrochemiluminescent label, collectable particles, binding reagents, and an electrolyte.

Abstract: A method for the detection of an analyte of interest in a sample, which method comprises the steps of: (1) forming a composition comprising (a) a sample, (b) at least one substance selected from the group consisting of (i) added analyte of interest or an analog of the analyte of interest, (ii) a binding partner of the analyte of interest or its said analog, and (iii) a reactive component capable of binding with (i) or (ii), wherein one of said substances is linked to a label compound having a chemical moiety capable of being induced to luminesce, and (c) a plurality of particles capable of specifically binding with the analyte and/or a substance defined in (b) (i), (b) (ii), or (b) (iii); (2) inducing the label compound to luminesce; and (3) measuring luminescence emitted by the composition to determine the presence of the analyte of interest in the sample.

Abstract: The use of impedance measurements to detect the presence of pathogens attached to antibody-coated beads. In a fluidic device antibodies are immobilized on a surface of a patterned interdigitated electrode. Pathogens in a sample fluid streaming past the electrode attach to the immobilized antibodies, which produces a change in impedance between two adjacent electrodes, which impedance change is measured and used to detect the presence of a pathogen. To amplify the signal, beads coated with antibodies are introduced and the beads would stick to the pathogen causing a greater change in impedance between the two adjacent electrodes.

Abstract: A system and method for removing contaminants from a surface. The system is designed to use very small particles having means thereon which are capable of selectively binding to a contaminant or contaminants of interest. The particles may contain a dye to render the particles visible in order for a user to observe the application and removal of the particles. The particles also have magnetic properties which may be provided by a high iron content. A carrier can be used to apply the particles to a surface whereupon the targeted contaminants bind to the particles. The particles may then be readily removed from the surface using magnets. When the particle is removed, the targeted contaminants are also removed. The invention is especially useful for the removal of contaminants from skin.

Abstract: This invention provides electromagnetic chips and electromagnetic biochips having arrays of individually addressable micro-electromagnetic units, as well as methods of utilizing these chips for directed manipulation of micro-particles and micro-structures such as biomolecules and chemical reagents. An electromagnetic biochip comprises an individually addressable micro-electromagnetic unit chip with ligand molecules immobilized on its surface. By controlling the electromagnetic field at each unit of the array and combining this control with magnetic modification of biomolecules, these chips can be used for directed manipulation, synthesis and release of biomolecules in order to increase sensitivity of biochemical or chemical analysis and reduce assay time. Other advantages with these chips include minimized damages to biological molecules and increased reproducibility of assay results.

Abstract: A method and apparatus for the manipulation of colloidal particulates and biomolecules at the interface between an insulating electrode such as silicon oxide and an electrolyte solution. Light-controlled electrokinetic assembly of particles near surfaces relies on the combination of three functional elements: the AC electric field-induced assembly of planar aggregates; the patterning of the electrolyte/silicon oxide/silicon interface to exert spatial control over the assembly process; and the real-time control of the assembly process via external illumination. The present invention provides a set of fundamental operations enabling interactive control over the creation and placement of planar arrays of several types of particles and biomolecules and the manipulation of array shape and size. The present invention enables sample preparation and handling for diagnostic assays and biochemical analysis in an array format, and the functional integration of these operations.

Abstract: The present invention relates to the finding and detection of Helicobacter pylori (H. pylori) antigens in blood of infected individuals. The H. pylori antigens are components of H. pylori cells which include, but not limited to DNA, RNA, and fragments of nucleotides, proteins or peptides. H. pylori DNA, RNA, and fragments of nucleotides can be detected by polymerase chain reaction (PCR), ligase chain reaction (LCR), or DNA hybridization methods or other amplification methods. H. pylori proteins or peptides or other antigenic components thereof can be detected by immunoassays or immunoblot using an antibody against H. pylori, preferably an antibody purified by an affinity column. The present invention further provides immunoassay methods, diagnostic kits, and an immunochromatographic assay device for detection of Helicobacter pylori antigens in serum samples.

Abstract: Diagnostic test devices, including diagnostic strip tests, are provided in which identifying information and the test result are machine-readable. Also provided are methods for obtaining identifying information and test results from the diagnostic test devices.

Abstract: Impedance measurements between the electrodes in an electric field is utilized to detect the presence of pathogens trapped in the electric field. Since particles trapped in a field using the dielectiphoretic force changes the impedance between the electrodes by changing the dielectric material between the electrodes, the degree of particle trapping can be determined by measuring the impedance. This measurement is used to determine if sufficient pathogen have been collected to analyze further or potentially to identify the pathogen.

Abstract: An ultrasonic energy source is used to provide a variable force for measuring the binding forces between molecular entities and for sensing the presence of an analyte in a test sample. The device includes a surface that has a first binding member attached thereto and one or more particles that have a second binding member attached thereto. A reaction vessel is provided for exposing the surface to the particles whereby, if the first binding member has a binding affinity for the second binding member, a complex is formed between individual first binding members and individual second binding members and the particles thereby become immobilized with respect to the surface. The ultrasonic energy source is positioned for applying a variable ultrasonic force onto the surface, and the position of the particles is monitored as the intensity of the ultrasonic force is varied.

Abstract: The present disclosure relates to a method for determining cholesterol in low density lipoprotein comprising the steps of (a) measuring total cholesterol level in a sample containing at least high density lipoprotein, low density lipoprotein, very low density lipoprotein and chylomicron, and (b) measuring cholesterol levels in the high density lipoprotein, very low density lipoprotein and chylomicron in the sample, wherein the cholesterol level in the low density lipoprotein is determined by subtracting a value obtained in the step (b) from a value obtained in the step (a). The present invention enables concurrent determination of cholesterol level in low density lipoprotein and total cholesterol level, facilitating acquisition of two types of biological information at a time.

Abstract: Method and apparatus for manipulating and monitoring analyte flowing in fluid streams. A giant magnetoresistive sensor has an array of sensing elements that produce electrical output signals which vary in dependence on changes in the magnetic field proximate the sensing elements. The analyte is included in a stream, such that the stream has a magnetic property which is dependent on the concentration and distribution on the analyte therein. The stream is flowed past the giant magnetoresistive sensor and in sufficiently close proximity to cause the magnetic properties of the stream to produce electrical output signals. The electrical output signals are monitored as an indicator of analyte concentration or distribution in the stream flowing past the GMR sensor. Changes in the magnetic field produced by the background stream are introduced by analyte molecules, whose presence in the flow past the GMR will effect the output reading.

Abstract: A chemical and bio-chemical assay method is described which screens compounds for enzyme inhibition, or receptor or other target binding. Inhibition or binding by the library compounds causes a change in the amount of an optically detectable label that is bound to suspendable cells or solid supports. The amounts of label bound to individual cells or solid supports are microscopically determined, and compared with the amount of label that is not bound to individual cells or solid supports. The degree of inhibition or binding is determined using this data. Confocal microscopy, and subsequent data analysis, allow the assay to be carried out without any separation step, and provide for high throughput screening of very small assay volume using very small amounts of test compound.

Abstract: In accordance with a first aspect, a binding assay comprises a machine-readable storage medium which supports a molecular receptor (22). In accordance with a second aspect, a support member (50) supports first (22) and second (24) molecular receptors and first (26) and second (28) data identifying the molecular receptors (22,24). In accordance with a third aspect, a support member has a first annular portion (106) to support molecular receptors and a second annular portion (108) to support machine-readable data identifying the plurality of molecular receptors.

Abstract: Novel magnetic assay methods and systems. According to a preferred embodiment, a chromatographic medium, which preferably comprises a test strip, is provided that is designed to be contacted with a test solution having activated magnetic particles such that the solution flows bilaterally thereacross. A magnetic field, generated by a magnet or electromagnet, is selectively applied to the medium which causes the charged particles to become substantially bound at a site on the medium specified by the position off the magnet, to thus form a captured line or zone. In one preferred embodiment, the magnetic field is applied at the site on the medium at which the test solution is contacted. The degree of magnetic force applied to the membrane may be selectively adjusted to vary the width or surface area of the capture line or zone.