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Apparatus and method for heating microfluidic volumes and moving fluidsRelated Patent Categories: Electric Heating, Heating Devices, Combined With Diverse-type Art Device, MirrorApparatus and method for heating microfluidic volumes and moving fluids description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060191887, Apparatus and method for heating microfluidic volumes and moving fluids. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application claims priority to U.S. patent application Ser. No. 10/765,536 entitled "Apparatus and method for heating microfluidic volumes and moving fluids" filed on Jan. 27, 2004 which is incorporated herein by reference in its entirety and which claims priority to U.S. Provisional Application Ser. No. 60/443,209, entitled "Method for heating microfluidic circuits and moving fluids", filed on Jan. 27, 2003 which is incorporated herein by reference in its entirety. FIELD OF THE INVENTION [0002] The invention relates generally to microfluidic devices and, in particular, microfluidic devices comprised of one or more heating elements having a resistance that varies with temperature. BACKGROUND OF THE INVENTION [0003] Manipulating fluidic reagents and assessing the results of reagent interactions are central to chemical and biological science. Manipulations include mixing fluidic reagents, assaying products resulting from such mixtures, and separation or purification of products or reagents and the like. Assessing the results of reagent interactions can include autoradiography, spectroscopy, microscopy, photography, mass spectrometry, nuclear magnetic resonance and many other techniques for observing and recording the results of mixing reagents. A single experiment can involve literally hundreds of fluidic manipulations, product separations, result recording processes and data compilation and integration steps. The effects of mixing fluidic reagents are typically assessed by additional equipment relating to detection, visualization or recording of an event to be assayed, such as spectrophotometers, autoradiographic equipment, microscopes, gel scanners, computers and the like. Fluidic manipulations are performed using a wide variety of laboratory equipment, including fluidic mixing devices, centrifugation equipment, molecule purification apparatus, chromatographic machinery, gel electrophoretic equipment and various fluid heating devices. [0004] An example of where heating devices are important is the amplification of nucleic acids which is central to the current field of molecular biology. Library screening, cloning, forensic analysis, genetic disease screening and other increasingly powerful techniques rely on the amplification of extremely small amounts of nucleic acids. As these techniques are reduced to a smaller scale for individual samples, the number of different samples that can be processed automatically in one assay expands dramatically. Microscale devices have evolved which can have few to hundreds of fluidly connected channels, conduits, chambers and wells for handling mircofluidic volumes. New integrated approaches for the handling and assaying of a large number of small samples are needed. [0005] In particular, new integrated approaches for the precise temperature control of microfluidic volumes are needed. For example, in the polymerase chain reaction (PCR) for nucleic acid amplification, a purified DNA polymerase enzyme is used to replicate the sample DNA in vitro. This system uses a set of at least two primers complementary to each strand of the sample nucleic acid template. Initially, the sample nucleic acid is heated to cause denaturation to single strands, followed by annealing of the primers to the single strands, at a lower temperature. The temperature is then adjusted to allow for extension of the primers by the polymerase along the template, thus replicating the strands. Subsequent thermal cycles repeat the denaturing, annealing and extending steps, which results in an exponential accumulation of replicated nucleic acid products. The accuracy and reproducibility of the microfluidic analyses can be highly dependent on the temperature of the fluid volume. Robust heating devices that can accurately control the temperature of microfluidic volumes are required. [0006] The concentration of fluids is another field where heating devices come into play. In many chemical and biochemical analysis methods performed using microfluidic devices, it is advantageous to concentrate an analyte as part of the analysis. For example, increased analyte concentration generally leads to increased chemical reaction rates, increased rates of mass transfer, and enhanced detectability. [0007] One general problem which has not been solved for microfluidics and which the present invention presents is an integrated, reproducible, and inexpensive temperature control for heating, thermal cycling, concentration of fluids, volume measurement, sensing and fluid transport. Prior art solutions in the form of "thermofoils" attempt to solve part of this problem but they involve incorporating resistance temperature detector devices or thermistors into the film and are therefore quite expensive. It is an object of the present invention to provide low-cost heating element that is affixable to a variety of temperature-sensitive devices. SUMMARY OF THE INVENTION [0008] According to one aspect of the invention, a device comprising a laminar body is provided. The laminar body includes a substrate having a first surface and a second surface. The laminar body includes at least one heating element disposed on the first surface. The heating element comprises a conductive layer that is patterned into at least two electrodes in a spaced relation to each other. The heating element also includes a resistive layer that includes a resistive material having a resistance that changes with temperature at a predetermined resistance temperature coefficient. The resistive layer is disposed to permit current to flow through the resistive material between the electrodes. The laminar body further includes at least one fluid-receiving location that corresponds to the location of the at least one heating element. The heating element is in thermal communication with the fluid-receiving location. [0009] According to another aspect of the invention a method for concentrating and measuring microfluidic volumes is provided. The method includes the step of providing a laminar body that includes a substrate with a first surface and a second surface. At least one heating element is disposed on the first surface of the substrate. The heating element comprises a conductive layer patterned into at least two electrodes in spaced relation to each other and a resistive layer comprising a resistive material having a resistance that changes with temperature at a predetermined resistance temperature coefficient. The resistive layer is disposed between the electrodes to permit current to flow through the resistive material between the electrodes to generate heat. The laminar body also includes at least one fluid-receiving location that corresponds to the location of the at least one heating element. The heating element is in thermal communication with the fluid-receiving location. The method further includes the steps of placing a volume of fluid at the fluid-receiving location and providing an electronics component having at least signal detection circuitry and control circuitry connected to the at least one heating element. The method further includes the step of applying a voltage across at least one heating element. Another step is obtaining at least one electrical information from at least one of the heating elements. The electrical information is a function of the variable resistance of the resistive material. The electrical information of at least one heating element is monitored. At least one heating element is controlled based on the electrical information that is calibrated to correspond to a known fluid volume or temperature and the fluid volume or temperature is determined. [0010] According to another aspect of the invention, a method for moving microfluids is provided. The method includes the step of providing a laminar body that comprises a substrate having a first surface and a second surface and at least one heating element disposed on the first surface. The heating element includes a conductive layer and a resistive layer. The conductive layer is patterned into at least two electrodes disposed in spaced relation to each other. The resistive layer comprises a resistive material having a resistance that changes with temperature at a predetermined resistance temperature coefficient. The resistive material is disposed between the electrodes to permit current to flow through the resistive material between the electrodes. The method includes the step of providing at least a first receiving location interconnected to a second receiving location. The heating element is located next to the first receiving location. The method includes the step of placing a volume of fluid in the second receiving location and placing a volume of gaseous fluid in the first receiving location. The method includes the step of heating the volume of gaseous fluid to expand and exert pressure on the volume of fluid in the second receiving location to move the volume of fluid in the second receiving location. The method includes the step of moving the volume of fluid. BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS [0011] The foregoing and other advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings in which: [0012] FIG. 1 is a perspective view of a device depicting a substrate, resistive material and conductive material according to the invention; [0013] FIG. 2 is a side elevational view along cross-section 2-2 of FIG. 1 according to the invention; [0014] FIG. 3 is a top view of circuit pattern of the conductive layer according to the invention; [0015] FIG. 4 is a perspective view of a laminar element having cone-shaped dimples according to the invention; [0016] FIG. 5 is a perspective view of a laminar element having spherically-shaped dimples according to the invention; [0017] FIG. 6 is an exploded view of a laminar element and a second body according to the invention; [0018] FIG. 7 is a perspective view of a laminar element and a second body according to the invention; [0019] FIG. 8 is a graph of electrical current and temperature behavior over time of a device according to the invention; Continue reading about Apparatus and method for heating microfluidic volumes and moving fluids... 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