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Magnetocaloric pump for microfluidic applicationsRelated Patent Categories: Pumps, By Heating Of Pumped FluidMagnetocaloric pump for microfluidic applications description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060292013, Magnetocaloric pump for microfluidic applications. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention relates to microfluidic pumps. More particularly, a magnetocaloric pump incorporated into an integrated circuit chip utilizes MnZnFe.sub.2O.sub.4 ferrofluid. The micropump requires only 35 mW power and operates at a temperature of only 40-80.degree. C. [0004] 2. Description of the Prior Art [0005] Microfluidic and lab-on-a-chip devices usually require some form of fluid pumping mechanism. While a great many pumping methods are known, there are only two basic approaches to pumping fluid at the microfluidic level. These are diaphragm and field-induced pumps. Diaphragm pumps use a small diaphragm on the chip that undergoes deformation to move the fluid. Passive valves or restrictions built into the channels control the direction of fluid flow. The diaphragms are deformed using a wide array of actuation technologies including piezoelectric, electromagnetic, electrostatic, thermopnuematics and shape memory alloys. There are two limitations to such approaches. First, the fluid flow is not continuous but pulsating. Second, the pump deforms a membrane at high frequency. Material fatigue limits the life cycle of the pump. [0006] The second approach to pumping fluids at the microfluidics scale utilizes external electric fields to propel the fluid. While this approach provides smooth flow, it generally requires high voltage which impacts electronics packaging and increases the overall system packaging size. [0007] The present invention is based on exploiting the magnetocaloric effect for pumping fluids at the microfluidic level. Many microfluidic applications require thermal cycling of the chemicals. In addition, there are presently many active research programs exploring the use of nanometer sized magnetic particles in chemical analysis systems. Our approach is based on exploiting both the thermal cycling and the magnetic/thermal behavior of the magnetic nanoparticles to provide a fluid propulsion system for microfluidic applications that requires no moving mechanical parts (high reliability) and can be powered with a low voltage, low current power source. The advantage of the low voltage, low current power source is that it will enable further miniaturization and mobility of future microfluidic systems. REFERENCES [0008] 1. E. L. Resler, Jr. and R. E. Rosensweig, "Regenerative Thermoelectric Power," in Journal of Engineering for Power/Transactions of the ASME, Vol. 89, pp. 399-406, July 1967. [0009] 2. R. V. Upadhyay, K. J. Davies, S. Wells and S. W. Charles, "Preparation-and Characterization of Ultra-fine MnFe.sub.2O.sub.4 and Mn.sub.xFe.sub.1-xFe.sub.2O.sub.4 Spinel Systems: I. Particles," in J. of Magnetism and Magnetic Materials Vol. 132, pp. 249-257, 1994. [0010] 3. C. Aston, "Biological Warfare Canaries," in IEEE Spectrum, Vol. 38, No. 10, pp. 35-40, October 2001. [0011] 4. D. J. Laser and J. G. Santiago, "A Review of Micropumps," in J. Micromechanics Microengineering., Vol. 14, pp. R35-R64, 2004. BRIEF SUMMARY OF THE INVENTION [0012] In a first preferred embodiment, a structure for pumping a ferrofluid comprises a fluid channel for containing a MnZnFe.sub.2O.sub.4ferrofluid; a localized heat source in the form of a joule heater near the fluid channel; and a magnetic source near the fluid channel such that the magnetic field of the magnetic source is partially coincident with the thermal field of the heat source. [0013] In another preferred embodiment, a structure for cooling a heat source comprises a fluid channel for containing a MnZnFe.sub.2O.sub.4ferrofluid; the fluid channel located near the heat source to be cooled; and a magnetic source located near the heat source such that the magnetic field of the magnetic source is partially coincident with the thermal field of the heat source, and the heat source is cooled by flow of the ferrofluid due to interaction of the heat source and magnetic source with the ferrofluid. [0014] In another preferred embodiment, a self-regulating method for cooling a heat source comprises the steps of locating a fluid channel containing a MnZnFe.sub.2O.sub.4ferrofluid near a heat source to be cooled; and locating a magnetic source near the heat source such that the magnetic field of the magnetic source is partially coincident with the thermal field of the heat source, and cooling of the heat source is due to flow of the ferrofluid caused by the interaction of the heat source and the magnetic source with the ferrofluid. BRIEF DESCRIPTION OF THE DRAWINGS [0015] FIG. 1 is a graph showing the temperature effect on magnetism for various materials. [0016] FIG. 2 illustrates the interaction of a magnetic field and a thermal field with a ferrofluid in a channel. [0017] FIG. 3 is a graph of the temperature variation in magnetization of a magnetite ferrofluid. [0018] FIG. 4 is a graph of the temperature variation in magnetization of a MnZn ferrofluid. [0019] FIG. 5 is an exploded view of magnetocaloric structure in accordance with the invention. [0020] FIG. 6 illustrates the interaction of a heat source, a magnetic source, and a ferrofluid to produce movement of the ferrofluid in a fluid channel. DETAILED DESCRIPTION OF THE INVENTION Continue reading about Magnetocaloric pump for microfluidic applications... Full patent description for Magnetocaloric pump for microfluidic applications Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Magnetocaloric pump for microfluidic applications patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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