This present invention relates to a device for providing a permanent source of energy through a temperature gradient in a living body, comprising a diode device.
The mammalian body is a natural producer of thermal energy. In recent years, researchers have looked towards the body as a potential source of usable energy. The conversion of a body's thermal energy into electric energy creates a potential for medical devices and wearable devices that are powered by body heat.
For example, U.S. Pat. No. 5,889,735 discloses a thermoelectrically powered wristwatch that utilizes a temperature difference between a human body and its surroundings to generate a voltage to power a device such as a wristwatch. Similar to the concept that a temperature difference exists between the body and its surroundings is the concept that there exists differences in temperature within one body. Further, U.S. Pat. No. 6,640,137 discloses a biothermal power source for a device implanted within the human body that is comprised of a thermoelectric module for converting thermal energy to electrical energy. This device is said to produce a power output of 100 microwatts from a temperature differential of between 1 to 5 degrees Celsius.
However, because thermoelectric devices are only 5-8% efficient, the low power output of such devices requires that thousands of thermocouples be built into one device in order to generate the energy necessary to power the device (or to continuously trickle-charge the batteries). This would be difficult to manufacture, and as of yet, only tens of thermocouples have been arrayed. Thus there is a need to provide a biothermal power source that has a higher percentage of practical efficiency
Recent technology has been developed to provide such a power source. FIGS. 1-5 illustrate some embodiments of such power sources having a higher percentage of practical efficiency.
U.S. Patent App. Pub. No. 2007/0013055 discloses a thermotunneling/thermionic converter. A preferred embodiment of this diode device is shown in FIG. 1 in which silicon wafers 100 and 102 have their inner surfaces substantially facing one another, and a spacer or plurality of spacers 104 positioned between them. Preferably, silicon wafers 100 and 102 have matching surfaces, that where one has an indentation the other has a protrusion. Thus when matched, the two surfaces are substantially equidistant from each other. In a preferred embodiment, a vacuum 106 is introduced. In this design, active piezo control is not required to maintain the gap, making the device inexpensive. The use of active elements is not required due to the mechanical properties of silicon, such that if a small particle is trapped in between two silicon wafers, a non-bonded area of 5000 times the size (height) of the particle is created. Therefore the spacers consisting of a dot of silicon oxide topped by a protective layer will have the effect of keeping the two silicon wafers at a desired distance.
U.S. Pat. No. 6,720,704 discloses a thermionic vacuum diode device with adjustable electrodes. A preferred embodiment of this diode device is depicted in FIG. 2, in which a first electrode 202, disposed on substrate 204, is attached to the end of actuator tube 90, and a second electrode 206, disposed on substrate 208, is attached to the other end of tube 90. The two electrodes are also connected to an electrical load or power supply 210 by means of wires 212. Actuator tube 90 has electrodes 92 disposed on its surface which are connected to controller 214 via wires 216. This controller sets the separation of electrodes 202 and 206. Electrodes 202 and 206 may also be connected to capacitance controller 218 which is able to assess the separation of the electrodes, and the separation of the electrodes may be accurately controlled via a feedback loop 220 to controller 214. Typically, the electrode separation is of the order of 0.1 to 100 nm. In a preferred embodiment, electrodes 202 and 206 may be formed as depicted in FIG. 3.
Referring now to FIG. 3, composite 80 is any material which has a similar thermal expansion coefficient to quartz and can be bonded to quartz. Preferably, composite 80 is a molybdenum disc. Electrically conducting paste 94, preferably silver paste, lies upon the upper surface of the molybdenum disc and is in contact with a composite 78. Composite 78 is preferably a matching electrode pair precursor, such as shown in step 130 of WO99/13562 or U.S. Pat. No. 6,417,060, or is more preferably a layer of titanium 72 deposited on substrate 70, and a layer of silver 74 further deposited on the layer of titanium. A further layer of copper 76 is grown electrochemically on the layer of silver. Ideally, substrate 70 is a silicon wafer, and is polished at least around its periphery where it is in contact with tube 90. Alternatively, composite 78 is composite 79 depicted in FIG. 4. Though upon formation and at first contact with paste 94, composite 78 is a single unit, high pressure followed by heat causes the composite to open, as depicted in FIG. 3, forming a pair of matching electrodes 72 and 74.
In a further embodiment, depicted in FIG. 4, substrate/composite 80 has a depression 82 across part of its surface. Substrate/composite 80 also has a locating hole 84 in its surface. An additional feature of this embodiment is alignment pin 86, which is premachined, and is attached to the composite 79 at the layer of copper 76. The diameter of the alignment pin is the same as the diameter of the locating hole which results in a tight fit between the alignment pin 86 and the locating hole 84 when the pin seats in the locating hole. The tight fit ensures that electrodes 72 and 74 do not slide relative to one another.
U.S. Patent App. Pub. No. 2005/0147841, as seen in FIG. 5, discloses an electrode for a diode device having an indented surface. The indents are formed on wafer 442 by means of laser, chemical or other means for etching a geometric pattern on the surface of solid materials such as silicon, metal, and the like. Preferably, the one or more indents should have a depth approximately 5 to 20 times a roughness of the material's surface and a width approximately 5-15 times the material's depth. It is also preferable that the indents be substantially sharp and substantially perpendicular to one another. Such indents alter the distribution of quantum states within a volume limited by a potential energy barrier and promote the transfer of elementary particles across a potential energy barrier. In one embodiment, the electrode is consists of a layer of silver 444 upon indented wafer 442, followed by a layer of titanium 446, upon which a layer of copper 448 is grown electrochemically to form a composite 450. When the composite 450 is opened, as shown in FIG. 5, it forms a pair of matching electrodes that can be utilized to make diode devices.
U.S. Pat. Nos. 6,281,514, 6,495,843, and 6,531,703 disclose methods for promoting the passage of electrons at or through a potential barrier comprising providing a potential barrier having a geometrical shape for causing de Broglie interference between electrons. In another embodiment, the invention provides an electron-emitting surface having a series of indents. The depth of the indents is chosen so that the probability wave of the electron reflected from the bottom of the indent interferes destructively with the probability wave of the electron reflected from the surface. This results in the increase of tunneling through the potential barrier. In further embodiments, the invention provides vacuum diode devices, including a vacuum diode heat pump, a thermionic converter and a photoelectric converter, in which either or both of the electrodes in these devices utilize said electron-emitting surface. In yet further embodiments, the invention provides devices in which the separation of the surfaces in such devices is controlled by piezo-electric positioning elements. A further embodiment provides a method for making an electron-emitting surface having a series of indents.
U.S. Pat. No. 6,680,214 and U.S. Pat. App. Pub. No. 2004/0206881 disclose methods for the induction of a suitable band gap and electron emissive properties into a substance, in which the substrate is provided with a surface structure corresponding to the interference of electron waves. Lithographic or similar techniques are used, either directly onto a metal mounted on the substrate, or onto a mold which then is used to impress the metal. In a preferred embodiment, a trench or series of nano-sized trenches are formed in the metal.
U.S. Pat. No. 6,117,344 discloses methods for fabricating nano-structured surfaces having geometries in which the passage of electrons through a potential barrier is enhanced. The methods use combinations of electron beam lithography, lift-off, and rolling, imprinting or stamping processes.
WO9964642 discloses a method for fabricating nanostructures directly in a material film, preferably a metal film, deposited on a substrate. In a preferred embodiment a mold or stamp having a surface which is the topological opposite of the nanostructure to be created is pressed into a heated metal coated on a substrate. The film is cooled and the mold is removed. In another embodiment, the thin layer of metal remaining attached to the substrate is removed by bombarding with a charged particle beam.
WO04040617 offers a method which blocks movement of low energy electrons through a thermoelectric material. This is achieved using a filter which is more transparent to high energy electrons than to low energy ones. A tunnel barrier on the path of the electrons is used as filter. The filter works on the basis of the wave properties of the electrons. The geometry of the tunnel barrier is such that the barrier becomes transparent for electrons having certain de Broglie wavelength. If the geometry of the barrier is such that its transparency wavelength matches the wavelength of high energy electrons it will be transparent for high energy electrons and will block low energy ones by means of tunnel barrier.
In WO03/083177, the use of electrodes having a modified shape and a method of etching a patterned indent onto the surface of a modified electrode are disclosed. The patterned indent increases the Fermi energy level inside the modified electrode, leading to a decrease in electron work function. FIG. 6 shows the shape and dimensions of a modified thin metal film 600. Indent 640 on metal substrate 600 has a width b and a depth a, and the separation between the indents is c. Preferably distances b and c are substantially equal. Preferably distance b is of the order of 2 μm or less. Experimental observations using a Kelvin probe indicate that the magnitude of a reduction in apparent work function increases as distance a is reduced. Utilization of e-beam lithography to create structures of the kind shown in FIG. 6 may allow indents to be formed in which distance b is 200 nm or less. Distance a is of the order of 20 nm or less, and is preferably of the order of 5 nm. Metal film 600 is given sharply defined geometric patterns or indents 640 of a dimension that creates a De Broglie wave interference pattern that leads to a decrease in the electron work function, thus facilitating the emissions of electrons from the surface and promoting the transfer of elementary particles across a potential barrier. The surface configuration of film 600 may resemble a corrugated pattern of squared-off, “u”-shaped ridges and/or valleys. Alternatively, the pattern may be a regular pattern of rectangular “plateaus” or “holes,” where the pattern resembles a checkerboard. The walls of indent 640 should be substantially perpendicular to one another, and its edges should be substantially sharp.
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