The applied voltage causes the piezoelectric layer 34 (FIG. At the end of the compression process, the electrical switch is opened whereby the piezoelectric layer 34 becomes a capacitor, storing any charge accumulated on the electrodes during the time the voltage was applied. At the end of the compression process, the electrical switch is opened whereby piezoelectric layer 34 becomes a capacitor that stores any charge accumulated on the electrodes 28 and 36 during the time period in which the voltage was applied. Micro-sensors that utilize piezoelectric films also have been used for mechanical to electrical transduction, however, such devices are not capable of producing usable electrical power to any significant degree. Unlike conventional large-scale heat pumps, vapor compression and adsorption machines, which utilize a throttling valve to expand the working fluid in an isenthalpic process, without producing any work, the micro-heat pump 60 produces work during the expansion process in the form of an electric current flowing from the electrodes 28, 36. By extracting work, the micro-heat pump 60 provides for the expansion of the working fluid 6 in a substantially isentropic process, which is significant for two reasons.
Tipos De Dolor Lumbar
FIG. 3 shows an enlarged cross-sectional view of a piezoelectric micro-heat pump having the same general construction of the micro-transducer of FIG. FIGS. 16A-16B are cross-sectional views of piezoelectric micro-transducer according to another embodiment configured for use as a micro-internal combustion engine. 1 shows an enlarged cross-sectional view of a piezoelectric micro-transducer according to one embodiment of the present invention. As with the heat engine 42, the first membrane 18 of the heat pump 60 completes one full oscillation during the cycle. During the second process, high-temperature heat-rejection, the high-temperature heat sink 64 is thermally coupled to second membrane 16 via thermal switches 68 to remove thermal energy from the heat pump 60 through conduction. 1, shown operating between a low-temperature heat source and a high-temperature heat sink. 20129779.doc 25/01/05 WO 02/084754 PCT/US01/51613 During the working cycle of the heat pump 60, low-temperature thermal energy is transferred into the heat pump 60 from the low-temperature heat source 62 by conduction.
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Micro-Heat Engine FIGS. 2A-2D illustrate the thermodynamic cycle of a heat engine 42 according to a one embodiment operating between a high-temperature heat source 44 and a low-temperature heat sink 46. In the illustrated embodiment, the high-temperature heat source 44 has thermal switches, or contacts, 48 operable to periodically thermally couple the first membrane 18 with the high-temperature heat source 44. Similarly, the low-temperature heat sink 46 has thermal switches, or contacts, 50 operable to periodically thermally couple the second membrane 16 with the low-temperature heat sink 46. The thermodynamic cycle of the heat engine 42, which is based on the Camot vapor cycle, consists of the following four processes: compression, high-temperature heat-addition, expansion and electrical power production, and low- WO 02/084754 PCT/US01/51613 temperature heat-rejection. Example In one example of a micro-heat engine 42, the first membrane 18 has a thickness of about 2 microns, the second membrane 16 has a thickness of about 5 microns, and the thickness of the engine cavity is about 25 microns.
Dolor Espalda Baja
The term “substrate” as used herein refers to any support material from which one or more microtransducers can be constructed and is not limited to materials, such as silicon wafers, conventionally used in the manufacture of semiconductor devices. This invention relates generally to micro-transducers having piezoelectric properties which can be used for converting energy in one form to useful energy in another form. As heat moves into the working fluid 6, some of the liquid portion 23 of the working fluid vaporizes, thereby increasing the volume the working fluid 6. This causes an upward displacement of the first membrane 18 and a current to flow from the electrodes 28 and 36. As in the heat-rejection process (process two), the temperature and pressure remain constant because the working fluid 6 is a saturated liquid and vapor mixture. Operating in a cascading arrangement is also desirable in that it is possible to select a working fluid 6 that is most appropriate for the pressure and temperature range of a particular level.
Dolor Neuropatico Curso
18, to flex downwardly toward the second membrane 16, thereby compressing the vapor 22. As the overall volume of the working fluid 6 decreases, the pressure of the working fluid 6 increases, which results in a corresponding increase in temperature. That is, each heat engine 42 in a particular level undergoes the same process of the thermodynamic cycle at the same time. 3, there is shown a heat pump 60, having the same general construction as the micro-transducer 10 of FIG. FIGS. 2A-2D illustrate the thermodynamic cycle of a piezoelectric micro-heat engine having the same general construction of the micro-transducer of FIG.
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The thermal switches 78 are positioned on the second membranes 16 to facilitate conduction of thermal energy from the first membranes 18 to respective second membranes 16 in an adjacent level of a lower temperature range. The second membrane 16 has a thickness greater than that of the first membrane 18, and therefore the second membrane 16 is generally more rigid than the first membrane. Second, the efficiency of the cycle can be increased if the electric current generated during the expansion is used to offset the power required to compress the working fluid 6 in the first process.
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- The device according to claim 17 wherein the transforming means comprises: a
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- The invention is technically feasible and commercially viable
Instead, heat is alternately transferred in and out of the heat engine via conduction through the second and first membranes 16, 18, while the working fluid remains inside the heat engine 42. In essence, the heat engine 42 functions as its own heat exchanger, which is a consequence of the large surfaceto-volume ratio that can be achieved on the micro-scale level.
However, because the device uses electrical power to heat and vaporize the working fluid and because there is no provision to cyclically heat and cool the working fluid, the device functions as an actuator, not as a true heat engine. Micro-scale heat engines are a particularly attractive option, because of the very high density energy storage afforded by the hydrocarbon fuels they bum.
Dolor De Garganta
In conventional large-scale heat engines and heat pumps, two-phase fluids cannot be used because surface tension causes the liquid portion of a two-phase saturated mixture to form small droplets that can quickly destroy thermal machinery during expansion and compression processes. Fabrication Methods for the Micro-Heat Engine and Micro-Heat Pump Using conventional micro-manufacturing techniques, an array of micro-transducers can be constructed from a pair of silicon wafers.
Tipos De Dolor Crónico
In particular, this stored spring energy can be used to achieve compression (process one, FIG. Dolor de seno izquierdo y espalda . 2B. In this process, the previously described electrical switch (not shown) is closed to allow for the removal of the electric charge stored in the electrodes 28 and 36 (FIG. According to another aspect of the invention there is provided a microtransducer comprising: a first layer; a second layer having piezoelectric properties and joined to the first layer so as to form a fluid-tight cavity therebetween; and a working fluid contained within the cavity, wherein the working fluid is a saturated mixture of vapour and liquid; wherein thermal energy flowing into the micro-transducer causes the working fluid to expand, thereby distending the second layer for generating an electrical charge. The thicknesses of the silicon layer 24 and the silicon oxide layer 26 of the first membrane 18 are about 600-nm and 400-nm, respectively.
Dolor Neuropatico Herpes
As heat is removed from the heat engine 42, some of the vapor 22 condenses, which causes a decrease in the volume of the working fluid 6. Such decrease in the volume of the working fluid 6 results in a return deflection of the first membrane 18 and a corresponding decrease in strain in the piezoelectric layer 34 (FIG. However, micro-machining is not restricted in its application to the formation of workpieces from silicon or other materials conventionally used in the manufacture of integrated circuits, and it is known to apply micromachining to other materials. Methods for manufacturing the micro-transducer 10 from a silicon wafer or other equivalent material are described in detail below. Endometriosis y dolor de espalda . Therefore, there exists a strong need for piezoelectric micro-transducers for use with MEMS and micro-electronic devices. In contrast, the lengths of the membranes desirably are relatively larger than their thicknesses, for example, between 1 to 5 mm, although larger or smaller membranes may be used.