Methods and systems of fabricating electrical devices by micro-molding

Abstract

To provide methods and systems of fabricating electrical devices by micro-molding.SOLUTION: The present invention generally relates to methods and systems of fabricating electrical devices by micro-molding, and more specifically to methods and systems of fabricating electrical devices having high resolution features using micro-molding processes. Systems of electrical devices with high-resolution components and methods of fabricating the electrical devices using micro-molding processes are described. Small footprint electrical devices can be achieved by fabricating components with highly conductive materials, and with closely spaced components.SELECTED DRAWING: Figure 10

Description

Technical Field

[0001] (Cross - Reference to Related Applications) This application claims the benefit of priority of U.S. Provisional Patent Application No. 63 / 036,357, filed on June 8, 2020, entitled "Small - Footprint Antenna Structure with High - Aspect - Ratio Conductors" and U.S. Provisional Patent Application No. 63 / 086,367, filed on October 1, 2020, entitled "Micro - Molded Gas Sensor". The disclosures of U.S. Provisional Patent Application No. 63 / 036,357 and No. 63 / 086,367 are hereby incorporated by reference in their entirety for all purposes.

[0002] The present invention generally relates to methods and systems for fabricating electrical devices by micro - molding, and more specifically, to methods and systems for fabricating electrical devices having high - resolution features using a micro - molding process.

Background Art

[0003] Micro - molding is a manufacturing process that can produce small, highly precise parts and components with micron tolerances. The process can be initiated by creating a mold having a cavity in the shape of the desired part. A thermoplastic material or resin can be rapidly injected into the cavity to create the part or component at high speed. Materials such as polyetheretherketone (PEEK), polyetherimide (PEI), carbon - filled liquid crystal polymer (LCP), or glass - filled nylon can be used in the micro - molding process. Soft durometer or elastomer resins can also be applied.

Summary of the Invention

Means for Solving the Problems

[0004] Systems and methods according to various embodiments of the present invention enable the design and fabrication of electrical devices, including (but not limited to) gas sensors, antennas, and inductors, using a microfabrication process. Many embodiments provide the design and structure of a microfabrication machine used in the microfabrication process. A microfabrication machine according to some embodiments can fabricate high-resolution electrical conductors with a high aspect ratio. Many embodiments utilize high aspect ratio components to produce compact, high-performance electrical devices in various configurations. Some embodiments provide methods for fabricating high-resolution and / or high aspect ratio components at low cost. Some embodiments provide that the microfabrication process provides a consistent, repeatable, and simplified manufacturing process.

[0005] Gas sensors and / or gas sensor elements fabricated using a microfabrication process according to some embodiments have lower power consumption, increased sensitivity, improved selectivity, increased consistency and controllability, and reduced footprint. Many embodiments provide the microfabrication of small footprint antennas, including (but not limited to) near-field antennas or far-field antennas. Some embodiments provide a compact antenna coil structure with high inductance and low series resistance for a given antenna footprint and conductor length. The high inductance and low series resistance of the antenna structure can be achieved, according to some embodiments, by fabricating an antenna coil with a highly conductive material and closely spaced high aspect ratio electrical conductors (traces). Some embodiments provide that the conductive components of an electrical device can be made from nanoparticles, including (but not limited to) metal nanoparticles.

[0006] One embodiment of the present invention is at least one gas sensor element, the at least one gas sensor element comprising a nanoporous electrical conductor, the nanoporous electrical conductor comprising molten nanoparticles, the at least one gas sensor element, at least one first electrode electrically connected to a first end of the at least one gas sensor element, and at least one second electrode electrically connected to a second end of the at least one gas sensor element, the at least one gas sensor element having a corresponding pair of first and second electrodes, and the electrical properties of the at least one gas sensor element measured by the at least one first electrode and the at least one second electrode changing in response to the ambient gas in contact with the nanoporous electrical conductor, including a microfabricated gas sensor.

[0007] In another embodiment, the microfabricated gas sensor further comprises a first gas sensor element and a second gas sensor element, the first gas sensor element comprising a first nanoparticle composition, and the second gas sensor element comprising a second nanoparticle composition different from the first nanoparticle composition.

[0008] In a further embodiment, the microfabricated gas sensor further comprises a first gas sensor element and a second gas sensor element, the first gas sensor element having a first shape factor, and the second gas sensor element having a second shape factor different from the first shape factor.

[0009] In yet another embodiment, the microfabricated gas sensor further comprises a microheater for heating the at least one gas sensor element.

[0010] In still a further embodiment, the microheater comprises a plurality of microheater sections that are individually controllable to provide different temperatures simultaneously in each of the plurality of microheater sections.

[0011] In yet a further embodiment, the microfabricated gas sensor also includes a sensor controller that is electrically connected to at least one first electrode and electrically connected to at least one second electrode, the sensor controller being operable to provide a current to at least one gas sensor element and measure its resistivity.

[0012] In another embodiment, the microfabricated gas sensor further includes a substrate, a microheater disposed on the substrate, and an electrical insulation layer disposed on the microheater, at least one first electrode and at least one second electrode being disposed on the electrical insulation layer, and at least one gas sensor element being disposed on a corresponding pair of first and second electrodes.

[0013] Again, in a further embodiment, at least one gas sensor element does not extend beyond the microheater.

[0014] In yet another further embodiment, the substrate incorporates at least one film, the film having a thickness of less than about 1 micron.

[0015] In another additional embodiment, the nanoparticles are selected from the group consisting of metal nanoparticles, metal oxide nanoparticles, and doped metal oxide nanoparticles.

[0016] Again, in another embodiment, the metal oxide nanoparticles are one or more of SnO2, TiO2, WO3, ZnO, In2O3, Cd:ZnO, CrO3, and V2O5.

[0017] Again, in yet a further embodiment, the metal oxide nanoparticles are doped with Al, Pt, Pd, Au, Ag, Ti, Cu, Fe, Sb, Mo, Ce, Mn, Rh2O3, or carbon nanotubes.

[0018] In yet another further embodiment, at least one gas sensor element has a height in the range of about 1 μm to about 20 μm and a width in the range of about 1 μm to about 50 μm.

[0019] In yet another embodiment, at least one gas sensor element has a surface roughness of less than about 100 nm RMS.

[0020] Again, in a further embodiment, the ratio between the element height of at least one gas sensor element and the element width of at least one gas sensor element is 2 or more.

[0021] In yet another embodiment, the ratio between the element height of at least one gas sensor element and the element width of at least one gas sensor element is 0.5 or less.

[0022] Again, in still a further embodiment, the ratio between the spacing between at least two adjacent gas sensor elements and the element width of at least one gas sensor element is 4 or less.

[0023] In still further additional embodiments, the micro-molded gas sensor further comprises at least one force electrode for injecting current or voltage into at least one gas sensor element and at least one sensing electrode for measuring a change in electrical characteristics.

[0024] Yet another additional embodiment includes a stamp having a first channel disposed on the surface of the stamp and a second channel disposed on the surface of the stamp, a first inlet port connected to the first channel and a second inlet port separate from the first inlet port connected to the second channel, a first nanoparticle ink supply source for supplying a first nanoparticle ink to the first inlet port and a second nanoparticle ink supply source separate from the first nanoparticle ink supply source for supplying a second nanoparticle ink to the second inlet port, wherein the first nanoparticle ink comprises a first nanoparticle composition and the second nanoparticle ink comprises a second nanoparticle composition different from the first nanoparticle composition, a pump or dispenser for pumping or dispensing the first nanoparticle ink through the first inlet port and the first channel and for pumping or dispensing the second nanoparticle ink through the second inlet port and the second channel, and a contact mechanism for contacting the surface of the stamp with a substrate, the micro - molding machine.

[0025] In another additional embodiment, the first channel has a first shape factor and the second channel has a second shape factor different from the first shape factor.

[0026] Again, a further embodiment includes an outlet port connected to the first or second channel, and the pump or dispenser is operable to provide a pressure below atmospheric pressure to the outlet port.

[0027] Again, another further embodiment is · providing a substrate having a substrate surface; · Providing a stamp comprising a mold layer having a support side and a channel side, and a support layer disposed in contact with the support side, wherein the mold layer comprises: (i) a first channel having a first shape factor disposed on the channel side, a first inlet port connected to the first channel, and a first outlet port connected to the first channel; and (ii) a second channel having a second shape factor disposed on the channel side, a second inlet port connected to the second channel, and a second outlet port connected to the second channel. · Providing a first nanoparticle ink comprising a first nanoparticle composition and a second nanoparticle ink comprising a second nanoparticle composition. · Disposing the mold layer in contact with the substrate surface. · Pumping or dispensing the first nanoparticle ink into the first channel through the first inlet port and pumping or dispensing the second nanoparticle ink into the second channel through the second inlet port. · Curing the first nanoparticle ink in the first channel to form a first nanoporous molten nanoparticle electrical conductor having electrical conductivity that varies in response to a first ambient gas in contact with the first nanoporous molten nanoparticle electrical conductor. · Curing the second nanoparticle ink in the second channel to form a second nanoporous molten nanoparticle electrical conductor having electrical conductivity that varies in response to a second ambient gas in contact with the second nanoporous molten nanoparticle electrical conductor. · Removing the stamp to form a self-standing gas sensor element on the substrate surface. Including a method of micro-molding a gas sensor element.

[0028] Again, in another embodiment, the first nanoparticle composition is different from the second nanoparticle composition, and the first shape factor is the same as the second shape factor.

[0029] In yet another further embodiment, the first nanoparticle composition is identical to the second nanoparticle composition, and the first shape factor is different from the second shape factor.

[0030] In still a further additional embodiment, the first nanoparticle composition is different from the second nanoparticle composition, and the first shape factor is different from the second shape factor.

[0031] In yet another embodiment, the support layer is more rigid than the mold layer.

[0032] In yet another additional embodiment, the channel has a height in the direction from the channel side to the mold layer, and the height exceeds the width of the channel on the channel side.

[0033] Again, a further embodiment includes heating the nanoparticle ink or exposing the nanoparticle ink to electromagnetic radiation to accelerate the curing step.

[0034] Yet a further embodiment includes sintering the nanoparticles by heating the nanoparticles or exposing the nanoparticles to electromagnetic radiation.

[0035] In yet another additional embodiment, providing an inlet pressure to the inlet port and an outlet pressure to the outlet port during the pumping or dispensing step, wherein the inlet pressure exceeds the outlet pressure.

[0036] In still a further embodiment, the step of pumping or dispensing the nanoparticle ink involves flowing the nanoparticle ink through the channel, and the flow of the nanoparticle ink is driven at least in part by capillary pressure within the channel.

[0037] Again, in yet another embodiment, the step of pumping or dispensing the nanoparticle ink involves flowing the nanoparticle ink through the channel, and the flow of the nanoparticle ink is driven by applying pressure to the inlet port or applying a vacuum to the outlet port.

[0038] In yet another further embodiment, the stamp comprises a material selected from the group consisting of polydimethylsiloxane, polymethylmethacrylate, and polyurethane.

[0039] In another further additional embodiment, at least one ink reservoir is incorporated into the stamp.

[0040] In yet another embodiment, the mold layer is reinforced by incorporation of nanoparticles or by inclusion of a fiber mesh comprising a material selected from the group consisting of glass, steel, carbon, and nylon.

[0041] Additional embodiments and features are described in part in the following description and will be, in part, apparent to those skilled in the art upon examination of this specification or can be learned by practice of the disclosure. A further understanding of the nature and advantages of the present disclosure can be realized by reference to the remaining portions of this specification and the drawings which form a part of this disclosure. The present invention provides, for example, the following items. (Item 1) A micro-molded gas sensor, At least one gas sensor element, wherein the at least one gas sensor element comprises a nanoporous electrical conductor, and the nanoporous electrical conductor comprises molten nanoparticles, at least one gas sensor element; At least one first electrode electrically connected to a first end of the at least one gas sensor element; At least one second electrode electrically connected to a second end of the at least one gas sensor element Comprising The at least one gas sensor element has a corresponding pair of first and second electrodes, The electrical properties of the at least one gas sensor element measured by the at least one first electrode and the at least one second electrode change in response to the ambient gas in contact with the nanoporous electrical conductor. Micro-molded gas sensor. (Item 2) The micro-molded gas sensor according to item 1, further comprising a first gas sensor element and a second gas sensor element, wherein the first gas sensor element comprises a first nanoparticle composition and the second gas sensor element comprises a second nanoparticle composition different from the first nanoparticle composition. (Item 3) The micro-molded gas sensor according to item 1, further comprising a first gas sensor element and a second gas sensor element, wherein the first gas sensor element has a first shape factor and the second gas sensor element has a second shape factor different from the first shape factor. (Item 4) The micro-molded gas sensor according to item 1, further comprising a micro-heater for heating the at least one gas sensor element. (Item 5) The micro-molded gas sensor according to item 4, wherein the micro-heater comprises a plurality of micro-heater sections that are individually controllable to provide different temperatures simultaneously in each of the plurality of micro-heater sections. (Item 6) The micro-molded gas sensor according to item 1, further comprising a sensor controller electrically connected to the at least one first electrode and electrically connected to the at least one second electrode, the sensor controller being operable to provide a current to the at least one gas sensor element and measure its resistivity. (Item 7) A substrate, A micro-heater disposed on the substrate, An electrical insulating layer disposed on the micro-heater Further comprising The at least one first electrode and the at least one second electrode are disposed on the electrical insulation layer, and the at least one gas sensor element is disposed on the corresponding first and second electrode pair. The micro-molded gas sensor according to item 1. (Item 8) The at least one gas sensor element does not extend beyond the micro-heater. The micro-molded gas sensor according to item 7. (Item 9) The substrate incorporates at least one film, and the film has a thickness of less than about 1 micron. The micro-molded gas sensor according to item 7. (Item 10) The nanoparticles are selected from the group consisting of metal nanoparticles, metal oxide nanoparticles, and doped metal oxide nanoparticles. The micro-molded gas sensor according to item 1. (Item 11) The metal oxide nanoparticles are SnO 2 , TiO 2 , WO 3 , ZnO, In 2 O 3 , Cd:ZnO, CrO 3 , and V 2 O 5 or more than one of them. The micro-molded gas sensor according to item 10. (Item 12) The metal oxide nanoparticles are doped with Al, Pt, Pd, Au, Ag, Ti, Cu, Fe, Sb, Mo, Ce, Mn, Rh 2 O 3 , or carbon nanotubes. The micro-molded gas sensor according to item 11. (Item 13) The at least one gas sensor element has a height in the range of about 1 μm to about 20 μm and a width in the range of about 1 μm to about 50 μm. The micro-molded gas sensor according to item 1. (Item 14) The at least one gas sensor element has a surface roughness of less than about 100 nm RMS. The micro-molded gas sensor according to item 1. (Item 15) The ratio between the element height of the at least one gas sensor element and the element width of the at least one gas sensor element is 2 or more. The micro-molded gas sensor according to item 1. (Item 16) The ratio between the element height of the at least one gas sensor element and the element width of the at least one gas sensor element is 0.5 or less. The micro-molded gas sensor according to item 1. (Item 17) The ratio between the spacing between at least two adjacent gas sensor elements and the element width of the at least one gas sensor element is 4 or less. The micro-molded gas sensor according to item 1. (Item 18) The micro-molded gas sensor according to item 1, further comprising at least one force electrode for injecting current or voltage into the at least one gas sensor element, and at least one sensing electrode for measuring a change in electrical characteristics. (Item 19) A micro-molding machine, A stamp having a first channel disposed on the surface of the stamp and a second channel disposed on the surface of the stamp, A first inlet port connected to the first channel and a second inlet port separate from the first inlet port and connected to the second channel, A first nanoparticle ink supply source for supplying a first nanoparticle ink to the first inlet port and a second nanoparticle ink supply source separate from the first nanoparticle ink supply source for supplying a second nanoparticle ink to the second inlet port, wherein the first nanoparticle ink comprises a first nanoparticle composition and the second nanoparticle ink comprises a second nanoparticle composition different from the first nanoparticle composition, the first nanoparticle ink supply source and the second nanoparticle ink supply source, A pump or dispenser for pumping or dispensing the first nanoparticle ink through the first inlet port and the first channel and for pumping or dispensing the second nanoparticle ink through the second inlet port and the second channel, A contact mechanism for bringing the surface of the stamp into contact with a substrate A micro-molding machine comprising. (Item 20) The micro-molding machine according to item 18, wherein the first channel has a first shape factor and the second channel has a second shape factor different from the first shape factor. (Item 21) The micro-molding machine according to item 18, further comprising an outlet port connected to the first or second channel, and the pump or dispenser being operable to provide a pressure below atmospheric pressure to the outlet port. (Item 22) A method for micro-molding a gas sensor element, Providing a substrate having a substrate surface, Providing a stamp comprising a mold layer having a support side and a channel side, and a support layer disposed in contact with the support side, wherein the mold layer comprises: (i) a first channel having a first shape factor disposed on the channel side, a first inlet port connected to the first channel, and a first outlet port connected to the first channel; and (ii) a second channel having a second shape factor disposed on the channel side, a second inlet port connected to the second channel, and a second outlet port connected to the second channel, the step; Providing a first nanoparticle ink comprising a first nanoparticle composition and a second nanoparticle ink comprising a second nanoparticle composition; Disposing the mold layer in contact with the substrate surface; Pressurizing or dispensing the first nanoparticle ink into the first channel through the first inlet port and pressurizing or dispensing the second nanoparticle ink into the second channel through the second inlet port; Curing the first nanoparticle ink in the first channel to form the first nanoporous molten nanoparticle electrical conductor having electrical conductivity that varies in response to a first ambient gas in contact with the first nanoporous molten nanoparticle electrical conductor; Curing the second nanoparticle ink in the second channel to form the second nanoporous molten nanoparticle electrical conductor having electrical conductivity that varies in response to a second ambient gas in contact with the second nanoporous molten nanoparticle electrical conductor; Removing the stamp to form a self-standing gas sensor element on the substrate surface; A method comprising. (Item 23) The method according to item 21, wherein the first nanoparticle composition is different from the second nanoparticle composition and the first shape factor is the same as the second shape factor. (Item 24) The method according to item 21, wherein the first nanoparticle composition is the same as the second nanoparticle composition and the first shape factor is different from the second shape factor. (Item 25) The method according to item 21, wherein the first nanoparticle composition is different from the second nanoparticle composition and the first shape factor is different from the second shape factor. (Item 26) The method according to item 21, wherein the support layer is more rigid than the mold layer. (Item 27) The method according to item 21, wherein the channel has a certain height in the direction from the channel side to the mold layer, and the certain height exceeds the width of the channel on the channel side. (Item 28) The method according to item 21, further comprising the step of heating the nanoparticle ink or exposing the nanoparticle ink to electromagnetic radiation to accelerate the curing step. (Item 29) The method according to item 21, further comprising the step of sintering the nanoparticles by heating the nanoparticles or exposing the nanoparticles to electromagnetic radiation. (Item 30) The method according to item 21, further comprising the step of providing an inlet pressure to the inlet port and an outlet pressure to the outlet port during the pumping or dispensing step, wherein the inlet pressure exceeds the outlet pressure. (Item 31) The method according to item 21, wherein the step of pumping or dispensing the nanoparticle ink involves flowing the nanoparticle ink through the channel, and the flow of the nanoparticle ink is driven at least partially by capillary pressure within the channel. (Item 32) The method according to item 21, wherein the step of pumping or dispensing the nanoparticle ink involves flowing the nanoparticle ink through the channel, and the flow of the nanoparticle ink is driven by applying pressure to the inlet port or applying a vacuum to the outlet port. (Item 33) The method according to item 21, wherein the stamp comprises a material selected from the group consisting of polydimethylsiloxane, polymethyl methacrylate, and polyurethane. (Item 34) The method according to item 21, wherein at least one ink reservoir is incorporated into the stamp. (Item 35) The method according to item 21, wherein the mold layer is reinforced by incorporation of nanoparticles or by inclusion of a fiber mesh comprising a material selected from the group consisting of glass, steel, carbon, and nylon.

Brief Description of the Drawings

[0042] The description will be better understood by reference to the following drawings, which are presented as exemplary embodiments of the invention and should not be construed as an exhaustive listing of the scope of the invention.

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[0066] The features and advantages of the present disclosure will become more apparent from the detailed description set forth below when considered in conjunction with the drawings, in which like reference characters identify corresponding elements throughout. In the drawings, like reference numbers generally indicate identical, functionally similar, and / or structurally similar elements. The figures are not drawn to scale, because the variation in size of the various elements of the figures is too great to permit depiction at actual scale. **DETAILED DESCRIPTION OF THE INVENTION**

[0067] Detailed Description Turning now to the drawings, a system and method for fabricating an electrical device using a micro molding process are described. Many embodiments provide the design and structure of a micro molding machine used in a micro molding process. According to some embodiments, the micro molding machine can fabricate high resolution electrical conductors with a high aspect ratio. The electrical conductors can be integrated into an electrical device, including (but not limited to) gas sensors, inductors, and antennas. Many embodiments provide that the micro molding machine includes at least a stamp. At least one ink supply can be provided to the stamp during the micro molding process. According to some embodiments, a plurality of ink supplies can supply the same and / or different inks to the micro molding stamp. In some embodiments, the micro molding machine has channels of the same and / or different form factors.

[0068] Many embodiments provide a micro-molding process for fabricating high aspect ratio electrical components and / or devices. Gas sensors and / or gas sensor elements processed using the micro-molding process according to some embodiments have lower power consumption, increased sensitivity, improved selectivity, increased consistency and controllability, and reduced footprint. Some embodiments provide that the micro-molding process provides a consistent, repeatable, and simplified manufacturing process. In certain embodiments, the gas sensor can include at least one gas sensor element. Many embodiments provide that a plurality of gas sensor elements can include the same or different materials and / or have the same or different form factors. In some embodiments, the gas sensor element can be disposed on a sensing electrode over at least one micro-heater. Some embodiments provide that the gas sensor element can be exposed to the ambient gas. In certain embodiments, the micro-heater can heat the gas sensor element. Some embodiments provide that the sensing electrode can measure the electrical characteristics of the gas sensor element. The gas sensor element can be a nanoporous electrical conductor made from (but not limited to) molten nanoparticles. According to many embodiments, the electrical characteristics of the gas sensor element can change in response to the ambient gas in contact with the nanoporous electrical conductor. The electrical characteristics can include (but are not limited to) resistivity, capacitance, inductance, phase, and any combination thereof.

[0069] In many embodiments, the microheater can provide heat to the gas sensor element to control the temperature of the gas sensor element. The heat can reduce the resistivity of the gas sensor element and enhance the interaction between the target gas molecules and the sensing material, and thus can increase the sensitivity of the sensor element to the target gas. In many embodiments, the microheater of the gas sensor can include individually controllable microheater compartments. The individually controllable microheater compartments according to some embodiments are individually controllable to provide different temperatures simultaneously in each microheater compartment, which can enable better selectivity of each sensing element towards its target gas. Some embodiments provide that each microheater compartment can be associated with and / or in thermal contact with a different gas sensor element. In such embodiments, the plurality of microheater compartments can simultaneously heat the corresponding gas sensor elements to different temperatures. The gas sensor elements heated to different temperatures according to many embodiments can be applied through individual and separate microheater electrodes to detect different gases and / or different concentrations of gases. By providing differently controllable and different gas sensor elements, the gas sensor can simultaneously measure different gases and / or different gas concentrations and can be used as a sensing device, including (but not limited to) an electronic nose.

[0070] Reducing the occupied area of the gas sensor element can, according to many embodiments, reduce the total area of the microheater without degrading the temperature uniformity of the gas sensor element. The power draw of the microheater can increase with area, and thus the reduction in the total area of the microheater results in a reduction in gas sensor power consumption and can facilitate the use of the gas sensor according to some embodiments in battery-powered electronic devices.

[0071] Many embodiments provide that the gas sensor element of a gas sensor can have a geometric shape that includes (but is not limited to) lines and straight lines, curves, or spirals. The gas sensor element can have different cross-sections that include (but are not limited to) squares, rectangles, cubes, circles, or cylinders. In some embodiments, the height H of the gas sensor element can exceed the width W of the element. In certain embodiments, the height H of the gas sensor element can be smaller than the width W of the element.

[0072] Multiple different gas sensor elements according to many embodiments can comprise electrical conductors made from the same or different nanoparticles. Different nanoparticle compositions of multiple different gas sensor elements according to certain embodiments can be sensitive to different gases and / or gas concentrations. Different nanoparticles according to some embodiments can include (but are not limited to) different nanoparticle materials, different nanoparticle dopings, different nanoparticle sizes, and any combination thereof. The nanoporous electrical conductors of different gas sensor elements according to some embodiments can have different nanoporosities that include (but are not limited to) nanopore size and the number of nanopores in the nanoporous electrical conductor. One embodiment provides that the nanoparticles of the gas sensor element can have diameters ranging from about 1 nm to about 1 micron.

[0073] Many embodiments provide that the nanoparticles of the gas sensor can include, but are not limited to, metal nanoparticles, metal oxide nanoparticles, or doped metal oxide nanoparticles. The metal oxide nanoparticles according to certain embodiments can include, but are not limited to, SnO2, TiO2, ITO, CdSe, WO3, ZnO, In2O3, Cd:ZnO, CrO3, V2O5, and any combination thereof. In some embodiments, the metal oxide nanoparticles can be doped with Al, Pt, Pd, Au, Ag, Ti, Cu, Fe, Sb, Mo, Ce, Mn, Rh2O3, or carbon nanotubes (CNTs) to improve the selectivity of the sensor. In some embodiments, the aggregate of nanoparticles can include a material that includes, but is not limited to, a non-conductive material and / or a dielectric material. The non-conductive material according to embodiments can be sensitive to gases and can affect the response of the conductive material in the nanoporous electrical conductor and / or can be useful for constructing the nanoporous electrical conductor. In some embodiments, the nanoparticle ink can be provided as a suspension in a liquid solvent that includes, but is not limited to, an aqueous dispersant and / or an organic solvent. According to some embodiments, the nanoparticles can have a viscosity in the range of about 0.3 centipoise to about 300 centipoise. In some embodiments, the nanoparticles can comprise different nanoparticles made from different conductive or non-conductive materials and can be distributed isotropically or anisotropically within the gas sensor element.

[0074] Many embodiments provide that the substrate of the gas sensor can include (but is not limited to) glass, polymer, semiconductor, ceramic, quartz, metal, paper, and / or sapphire. In some embodiments, the substrate for the gas sensor can be a printed circuit board (PCB) substrate or a liquid crystal polymer (LCP) material. Some embodiments provide that the substrate can be rigid, flexible, and / or substantially planar. In some embodiments, the substrate can be found in the display, integrated circuit, electronic device assembly, or circuit board industries. In some embodiments, the substrate may contain CMOS and / or MEMS devices, integrated circuits, microprocessors, microcontrollers, angle measurement circuitry, RF circuits, and transceivers.

[0075] Many embodiments provide a high aspect ratio antenna that includes an inductor processed using (but not limited to) a microfabrication process. Many embodiments provide that the high aspect ratio antenna includes an induction coil. According to some embodiments, the induction coil has a spiral and / or helical arrangement of a conductive electrical material. In some embodiments, the electrical conductor has a high aspect ratio. In many embodiments, an antenna with a high aspect ratio conductor increases the cross-sectional area of the conductor for a given conductor width and thus reduces the electrical resistance of the antenna. Some embodiments provide that the antenna footprint can be significantly reduced.

[0076] In many embodiments, the high aspect ratio electrical conductors are arranged in various configurations for high performance inductors and antennas, including (but not limited to) near field antennas. Some embodiments provide that electrical wires and / or traces can be arranged in configurations including (but not limited to) planar rectangular, circular, and / or hexagonal spirals on a substrate to form a coil. Antennas according to many embodiments can have a cross-section including (but not limited to) rectangular, triangular, quadrilateral, or those with curved surfaces. In some embodiments, the coil can extend in a direction normal to the substrate such that the conductor has an increased aspect ratio. The antenna can be electrically connected to a circuit that operates or responds to the antenna. Many embodiments provide that the high aspect ratio antenna can be integrated into an electronic circuit, including (but not limited to) a tuned antenna system. In some embodiments, components including (but not limited to) circuits, integrated circuits (ICs), resistors, and capacitors can be incorporated into the antenna system. According to some embodiments, the additional components can be installed inside and / or outside the coil. In some embodiments, the components can be installed in different circuit planes.

[0077] In some embodiments, some coils can be stacked to increase the inductance of the coil. In many embodiments, the high aspect ratio antenna can be a multi-layer antenna. According to some embodiments, each antenna layer can be separated by an insulator from an adjacent layer and can be connected through electrical vias. In some embodiments, the inductance of a multi-layer coil structure can be improved compared to a single-layer coil. According to some embodiments, the coils can be located in the same plane and / or on the same substrate. In some embodiments, the coils can be installed on subsequent planes and / or substrates along the same axis. The design of the coil can be symmetric and / or asymmetric according to some embodiments.

[0078] In many embodiments, an antenna coil with a high aspect ratio has a small footprint and exhibits high inductance and low series resistance. Some embodiments provide that the high inductance and low series resistance of the antenna structure can be achieved by fabricating an antenna coil with a high aspect ratio trace that involves a highly conductive material and is closely spaced. Some embodiments provide that the conductive traces of the high aspect ratio antenna can be made from particles including (but not limited to) conductive particles, metal nanoparticles, non-conductive (dielectric) particles, and semi-conductive particles. In some embodiments, the particles comprise nanoparticles made from different conductive and / or non-conductive materials. In some embodiments, the nanoparticles can be distributed isotropically and / or anisotropically in the antenna. Examples of metal nanoparticles include (but are not limited to) silver, copper, gold, nickel, and any combination thereof. Examples of semi-conductive particles include (but are not limited to) metal oxide particles. Many embodiments provide that the particles can be provided as a suspension in a liquid solvent. According to some embodiments, the nanoparticles can have a diameter in the range of about 1 nm to about 5 μm.

[0079] Many embodiments provide that the high aspect ratio antenna structure can include a plurality of antennas including (but not limited to) a coil antenna disposed on a substrate. Some embodiments provide that the high aspect ratio antenna can be constructed using a micro mold stamp. In many embodiments, the high aspect ratio conductor can be constructed from a nanoparticle ink cured within a channel disposed within a micro mold stamp applied on the substrate surface. This process enables the antenna and inductor to be fabricated with dimensions suitable for small and portable electronic devices. Some embodiments provide that the antenna and conductor have dimensions in the range of about 1 μm to about 100 μm. In one embodiment, the antenna has an aspect ratio (ratio of conductor height to conductor width) greater than 1.

[0080] Many embodiments provide a micro - molding process for fabricating high aspect ratio antennas. Some embodiments incorporate a micro - molding machine that includes a micro - molding stamp when fabricating the antenna. In certain embodiments, the micro - molding stamp can print a high aspect ratio conductor with nanoparticles on a substrate to form a high aspect ratio antenna. Many embodiments provide that a well - controlled surface roughness of the micro - molding stamp and a small size of the nanoparticle ink enable a root - mean - square surface roughness of the aspect ratio that is much smaller than the skin depth of the conductor. In some embodiments, the signal generated in the antenna has reduced signal attenuation at high frequencies (1 MHz to 1 THz). At high frequencies (frequencies above 1 MHz), the skin effect can become significant. For example, in the UHF band, the skin depth is on the order of a few microns, and most of the current can flow within a distance of about 5 times the skin depth of the conductor's surface. The surface roughness of the conductor can thus lead to a measurable change in resistance, which in turn leads to an increase in signal attenuation. Generally, the root - mean - square surface roughness should be much smaller than the skin depth of the electric field in the conductor to avoid additional attenuation of the signal. Some embodiments provide that the micro - molding stamp has a well - controlled surface roughness and the nanoparticles have a small size. The printed electrical conductors of the high aspect ratio antennas according to many embodiments have a significantly reduced root - mean - square surface roughness compared to conventional manufacturing methods, including (but not limited to) screen printing and ink - jet printing. Some embodiments provide that the surface roughness of the antenna can be much less than the skin depth of the conductor and the signal generated in the antenna has reduced signal attenuation at high frequencies (frequencies from about 1 MHz to about 1 THz).

[0081] Many embodiments provide a micro - molding method for manufacturing high aspect ratio antennas and / or coils at reasonable costs. In some embodiments, an antenna with a high aspect ratio conductor can be processed as a self - standing structure formed or deposited on a substrate. Some embodiments provide that the substrate can be a printed circuit board (PCB) substrate. The substrate can be found in a display, an integrated circuit, an electronic device assembly, or the circuit board industry according to certain embodiments. In some embodiments, the substrate may contain CMOS and / or MEMS devices, integrated circuits, microprocessors, microcontrollers, angle measurement circuitry, RF circuits, and transceivers.

[0082] In some embodiments, a high aspect ratio antenna can be deposited on a dielectric substrate. According to certain embodiments, most of the current may flow along the interface between the dielectric substrate and the antenna. In such embodiments, a small surface roughness of the substrate / antenna interface enables a correspondingly low resistance in the antenna. According to some embodiments, a method for fabricating a high aspect ratio antenna provides a smooth interface with a small surface roughness without electroplating. Electroplating can reduce the resolution of the structures formed on the substrate. In some embodiments, a thin electroplating layer disposed in one plating step can be used to provide a conductive coating on the conductor surface. According to some embodiments, the conductive coating can be thin enough not to obscure the particulate structure of the conductor. Thus, the conductor surface can have a non - planar particulate definition of protrusions and depressions that conformally follows the contour of the underlying nanoparticle structure and exposes the nanoparticle structure of the conductor. Some embodiments provide that a thin conductive layer can improve the skin conduction of the electrical conductor while limiting the loss of the spatial resolution of the electrical conductor.

[0083] High aspect ratio antenna structures, according to many embodiments, enable longer and more responsive antennas that improve signal response. In some embodiments, antenna windings can be formed closer together. Some embodiments provide that antenna windings can be formed closer to an electroplated structure.

[0084] In many embodiments, a high aspect ratio antenna structure provides the same inductance with a reduced conductor line spacing for a given aspect ratio of the antenna in a smaller area with a smaller footprint. High aspect ratio antennas, according to some embodiments, provide increased inductance and signal sensitivity with a reduced conductor line spacing and more turns, for a given aspect ratio of the antenna, compared to an antenna with the same footprint but with a low aspect ratio. In some embodiments, the aspect ratio of the conductor provides an increase in capacitance proportional to the aspect ratio.

[0085] Many embodiments provide that high aspect ratio coil structures with high conductivity can be applied to the design and fabrication of high Q low loss air core inductors in high frequency electronic circuit design. In some embodiments, the coil structure can be applied as an inductor in fields including (but not limited to) switched mode power supplies, radio frequency (RF) band pass, high pass, and low pass filters, low loss transformers, inductive angle and position sensors, LC or RLC resonators. Printed inductors and / or coils, according to some embodiments, can be integrated as discrete components, as part of a larger distributed element network, and / or as microstrips containing multiple passive components. Some embodiments provide that the high accuracy of printed inductors and / or coils can provide benefits including (but not limited to) more accurate tuning of resonance frequencies, smaller footprint, sub-quarter wavelength filtering, and higher power coupling efficiency.

[0086] Although certain implementations of the embodiments have been described, it will be apparent to those skilled in the art that other implementations incorporating the concepts of the present disclosure may also be used. Accordingly, the present disclosure should not be limited to a particular implementation, but rather should be limited only by the spirit and scope of the following claims.

[0087] Throughout the description, when an apparatus and system are described as having, including, or comprising specific components, or when a process and method are described as having, including, or comprising specific steps, in addition, there exist apparatuses and systems of the disclosed technology that consist essentially of, or consist of, the recited components, and there exist processes and methods according to the disclosed technology that consist essentially of, or consist of, the recited processing steps.

[0088] It should be understood that the order of steps or the order for performing certain actions is not important as long as the disclosed technology remains operable. Also, two or more steps or actions can be performed simultaneously in some situations. Although the invention has been described in detail with particular reference to certain embodiments thereof, it should be understood that variations and modifications can be affected within the spirit and scope of the invention. (Gas sensor)

[0089] A gas sensor can be used to detect ambient gas and measure the gas concentration present in the atmosphere. The gas of interest can include toxic, explosive, or environmental gases. The gas sensor may be used in various applications including industrial manufacturing, chemical process control, environmental protection, personal health monitoring, smart city monitoring, indoor / outdoor air quality control, and national defense.

[0090] A gas sensor can rely on changes in the attributes of a gas sensor element that is exposed to a target gas to which the corresponding gas sensor element is sensitive. Gas sensors include a variety of different sensing architectures that convert the sensed gas into an electrochemical, optical, acoustic, thermometric, or gravimetric signal. Among these, the electrically converted gas sensor is one of the widely studied ones and is one of the common sensors. An electric gas sensor may include two main components, namely, a sensing material with a gas sensor element and a transducer. The sensing material in the gas sensor element may be exposed to the ambient atmosphere, and when the target gas is detected, it undergoes a change in one or more of its physical properties such as conductivity, work function, or permittivity of the material. After the sensing material interacts with the target gas, the transducer converts the changed physical property into a change in the electrical characteristics of the sensing material such as capacitance (C), inductance (L), or resistance (R). The circuit then measures the magnitude, frequency (F), or phase (φ) variation of the current (I) or voltage (V) corresponding to the change in the electrical characteristics of the sensing material.

[0091] Gas sensors that are electrically converted can be classified into at least four different device architectures, namely, resistance, capacitance, inductance, and field-effect-based gas sensor architectures. Electronic gas sensing materials are generally conductors or semiconductors and undergo a change in their electrical properties when exposed to the target gas. Typical gas sensing materials include metal oxide semiconductors, conductive polymers, carbon nanotubes, and 2D materials. Most commercial gas sensors are based on metal oxide semiconductor sensing layers, such as NiO, SnO2, TiO, WO3, Fe2O3, and ZnO.

[0092] Metal oxide gas sensors can be thick-film devices with a sensing layer thickness ranging from 1 μm to 100 μm or thin-film devices with a sensing layer thickness ranging from a few nm to 1 μm. The gas sensing properties of thin and thick-film metal oxide-based gas sensors of nominally the same material exhibit significantly different responses to various gases in different temperature ranges.

[0093] Different techniques are currently being used to deposit thin and thick film layer metal oxide sensing films. Deposition methods for thin film deposition include vacuum deposition techniques such as physical vapor deposition, atomic layer deposition, molecular vapor deposition, thermal chemical vapor deposition, or flame spray pyrolysis. Thick film deposition techniques include screen printing, inkjet printing, drop casting, and electrohydrodynamic printing. Highly effective metal oxide gas sensors can include nanostructured materials deposited as thick porous films on transducer electrodes.

[0094] Most commercial gas sensors may require a heater to sensitize the gas sensor element to the gas. Since most gas sensors are intended for portable applications, power usage by the gas sensor and the physical size of the gas sensor can be important performance attributes.

[0095] In previous research, Graf et al. have discussed gas - sensitive metal oxide materials containing wide - bandgap semiconducting oxides such as tin oxide, gallium oxide, indium oxide, or zinc oxide. (See, for example, M. Graf, et al., Journal of Nanoparticle Research, 2006, 8, 823 - 839, the disclosure of which is incorporated herein by reference in its entirety.) Generally, gaseous electron donors or acceptors adsorb onto the metal oxide, forming surface states that can exchange electrons with the semiconductor metal oxide. Acceptor molecules can extract electrons from the metal oxide semiconductor and thus decrease its conductivity. The opposite is true for electron - donating molecules. A space - charge layer can thus be formed. By varying the surface concentration of the donor / acceptor, the conductivity of the space - charge region can be modulated such that the conductivity of the metal oxide semiconductor material changes in response to changes in the analyte gas concentration. These chemically induced changes can then be converted into an electrical signal using a simple electrode structure for conductivity measurement.

[0096] The gas sensor element can comprise a thin film formed by evaporation, or a thick film formed by drop casting or screen printing a metal oxide gas sensor element, or by depositing metal oxide nanoparticles in solution using an inkjet printer on a microheater. The gas sensor element can be constructed using the micro-in-capillary molding (MIMIC) method. (See, e.g., M. Heule, et al., Adv. Mater., 2001, 13, 23, 1790-1793 and M. Heule, et al., Sensors and Actuators B, 2003, 93, 1-3, 100-106, the disclosures of which are incorporated herein by reference in their entireties.) However, such gas sensors can vary widely, have inconsistent performance, and consume more power than desired. Also, for example, gas sensors that can simultaneously sense various gases, such as in an electronic nose, can be useful.

[0097] Many embodiments provide a gas sensor processed using a micro-molding process. According to some embodiments, the gas sensor has a smaller size and exhibits reduced power consumption. Some embodiments provide that the gas sensor is more consistent in performance. In some embodiments, the gas sensor includes a wide variety of gas sensor elements. According to some embodiments, the micro-molding processing process is a simple and repeatable manufacturing process. A gas sensor system with a high-resolution gas sensor element processed using a micro-molding process according to various embodiments of the present invention is further discussed below. (Micro-molded gas sensor)

[0098] Many embodiments provide a structure and method for fabricating a gas sensor. According to some embodiments, the gas sensor has lower power consumption, increased sensitivity, improved selectivity, increased consistency and controllability, reduced footprint, and a simplified manufacturing process. The footprint of the gas sensor is the area of the gas sensor over the substrate on which the gas sensor is disposed. At least one gas sensor element can be constructed on a substrate using a microfabrication process according to some embodiments. Many embodiments provide that the gas sensor elements can include different materials and / or have different form factors. In some embodiments, the gas sensor element can be disposed on a sensing electrode over at least one microheater. The gas sensor element on the sensing electrode can be exclusive and direct over at least one microheater. Some embodiments provide that the gas sensor element can be exposed to the ambient gas. In one embodiment, the microheater can heat the gas sensor element. Some embodiments provide that the sensing electrode can measure the electrical characteristics of the gas sensor element.

[0099] Many embodiments provide a structure of a gas sensor fabricated using a micro - molding process. In some embodiments, at least one element of the gas sensor can be fabricated using a micro - molding process. A micro - molded gas sensor can include at least one gas - sensor element. The gas - sensor element can be a nanoporous electrical conductor made from (but not limited to) molten nanoparticles. According to some embodiments, the molten nanoparticles can be sintered or welded nanoparticles. In some embodiments, the micro - molded gas sensor includes a plurality of gas - sensor elements. The gas - sensor element can have an element length L, an element height H, and an element width W. In some embodiments, the gas - sensor element height H can exceed the element width W. In one embodiment, an electrode can be electrically connected to the gas - sensor element. Some embodiments refer to the electrode as a gas - sensor electrode. In some embodiments, additional current and / or voltage injection force electrodes can be incorporated. According to some embodiments, the force electrode can be connected to the gas - sensor element and provide a four - point probe measurement configuration. Such embodiments can improve the long - term stability of the gas sensor by reducing or eliminating the effect of contact resistance between the sensing elements for measurement. According to many embodiments, the electrical properties of the gas - sensor element can change in response to the ambient gas in contact with the nanoporous electrical conductor. The electrical properties can include (but not limited to) resistivity, capacitance, inductance, phase, and any combination thereof. In some embodiments, the gas sensor can include a sensor controller electrically connected to the electrodes. In some embodiments, the sensor controller can be operable to provide a current to the gas - sensor element through the electrodes and / or other electrical connections to the gas - sensor element and measure its resistivity.

[0100] In some embodiments, the gas sensor can include a plurality of gas sensor elements that can be substantially the same (e.g., within manufacturing tolerances). The plurality of substantially the same gas sensor elements according to some embodiments can provide redundant measurements that can be combined to reduce variability in gas sensor measurements and improve consistency and accuracy. Some embodiments provide that each gas sensor element can be connected to a sensor controller by a separate first electrode and a separate second electrode. Some embodiments provide that the gas sensor elements can be electrically connected to a common first electrode and / or a common second electrode.

[0101] Many embodiments provide that the gas sensor can be disposed on at least one microheater on a substrate. In some embodiments, the microheater can be an electrical microheater. In some embodiments, the electrical microheater can include at least one microheater electrode that includes (but is not limited to) a resistive electrical conductor or a resistive wire. Some embodiments provide that at least one electrical insulating layer that includes (but is not limited to) a dielectric layer or a SiO2 layer can be disposed on the microheater and the gas sensor element can be disposed on the insulating layer. The insulating layer according to some embodiments can electrically insulate and protect the gas sensor element from the microheater electrode. In some embodiments, the microheater can extend beyond the gas sensor element in one or two orthogonal directions such that the gas sensor element can be surrounded by the microheater in a horizontal direction parallel to the surface on or across the substrate. Some embodiments provide that the surface can be the surface of the substrate on which the gas sensor element is disposed or the surface of any layer disposed on the substrate on which the gas sensor element is disposed. By uniformly heating a portion of the gas sensor element by the microheater located between the sensing electrode and / or the force electrode, the temperature of the gas sensor element can be more consistent and better controlled and, according to some embodiments, can provide more reliable and consistent electrical property measurements.

[0102] In many embodiments, the microheater can provide heat to the gas sensor element to control the temperature of the gas sensor element. The heat can reduce the resistivity of the gas sensor element and enhance the interaction between the target gas molecules and the sensing material, and thus can increase the sensitivity of the sensor element to the target gas. In some embodiments, the gas sensor element can operate more effectively at elevated temperatures, including ambient temperatures (e.g., but not limited to) from about 150 °C to about 350 °C and / or temperatures above room temperature. The microheater according to an embodiment can be electrically connected to and controlled by a sensor control device.

[0103] A plan view of a gas sensor according to an embodiment of the present invention is illustrated in FIG. 1. The microfabricated gas sensor 99 includes at least one gas sensor element 10. The gas sensor element 10 can include a nanoporous electrical conductor comprising molten nanoparticles. The gas sensor element 10 can have an element length L, an element height H, and an element width W. At least a first electrode 30A can be electrically connected to the gas sensor element 10, for example, at a first end of the gas sensor element 10. At least a second electrode 30B can be electrically connected to the gas sensor element 10, for example, at a second end of the gas sensor element 10 opposite the first end. The first electrode 30A and the second electrode 30B are collectively referred to as the gas sensor electrodes 30. The electrical properties of the gas sensor element 10 change in response to the ambient gas in contact with the nanoporous electrical conductor. In some embodiments, the gas sensor 99 can include a sensor controller 74 that is electrically connected to the first electrode 30A and electrically connected to the second electrode 30B. The sensor controller 74 can be operable to provide a current to the gas sensor element 10 and measure its resistivity, for example, through the first electrode 30A and the second electrode 30B or other electrical connections to the gas sensor element 10.

[0104] In FIG. 1, the gas sensor 99 can include a substrate 20 and a microheater 90 disposed on the substrate 20. The electric microheater 90 can include at least one microheater electrode 92 such as a resistive electrical conductor or a resistive wire disposed on the substrate 20. The microheater 90 can be electrically connected to and controlled by a sensor control device 74.

[0105] A cross-sectional view of the gas sensor obtained along the cross-section line A of FIG. 1 according to an embodiment of the present invention is shown in FIG. 2. The microfabricated gas sensor 99 includes at least one gas sensor element 10. The gas sensor element 10 can include a nanoporous electrical conductor including molten nanoparticles 12. The molten nanoparticles 12 can be sintered or welded nanoparticles 12. The gas sensor element 10 can have an element length L, an element height H, and an element width W. The element height H can exceed the element width W.

[0106] In FIG. 2, the gas sensor 99 can include a substrate 20. A microheater 90 including a microheater electrode 92 such as a resistive electrical conductor or a resistive wire can be disposed on the substrate 20. An electrical insulating layer 96 (for example, a dielectric such as SiO2) can be disposed on the microheater 90, and the gas sensor element 10 can be disposed on the insulating layer 96. The insulating layer 96 electrically insulates and protects the gas sensor element 10 from the microheater electrode 92. The microheater 90 can extend beyond the gas sensor element 10 such that the gas sensor element 10 is surrounded by the microheater 90 in a horizontal direction parallel to the surface 22 on or across the substrate 20. By surrounding the gas sensor element 10 with the microheater 90, the temperature of the gas sensor element 10 can be made more consistent and better controlled, providing more reliable and consistent electrical property measurements. FIGS. 1 and 2 illustrate specific gas sensor structural schemes and gas sensor element compositions, but any configuration and design can be appropriately utilized according to the specific requirements of a given application.

[0107] Many embodiments provide that gas sensors fabricated using a microfabrication process can include mutually different gas sensor elements. Some embodiments provide that a plurality of different gas sensor elements in a gas sensor can provide measurements of different gases and / or gas concentrations in a single gas sensor. Some embodiments implement a gas sensor in an electronic nose. The plurality of different gas sensor elements according to many embodiments can comprise electrical conductors made from different nanoparticles. The different nanoparticle compositions of the plurality of different gas sensor elements according to an embodiment can be sensitive to different gases and / or gas concentrations. In some embodiments, the selectivity of a gas sensor element can be characterized by the ratio of the change in the output signal in the presence of the target gas to the change in the output signal when a different gas is present.

[0108] In many embodiments, the plurality of different gas sensor elements of a gas sensor can be made from different nanoparticles. The different nanoparticles according to some embodiments can include (but are not limited to) different nanoparticle materials, different nanoparticle dopings, different nanoparticle sizes, and any combination thereof. The nanoporous electrical conductors of different gas sensor elements according to some embodiments can have different nanoporosities, including (but not limited to) the nanopore size and the number of nanopores in the nanoporous electrical conductor.

[0109] In some embodiments, the gas sensor elements of a gas sensor can have the same and / or different shape factors from other gas sensor elements of the same gas sensor. Examples of shape factors include (but are not limited to) the length of the gas sensor element, the height of the gas sensor element, the width of the gas sensor element, and the element shape.

[0110] Many embodiments provide that a gas sensor element can have an element height H that exceeds an element width W. In some embodiments, the ratio between the element height H and the element width W can be up to 2 and can also exceed 2. In some embodiments, the ratio between the element height H and the element width W can be up to 4 and can also exceed 4, up to 8 and can also exceed 8, up to 16 and can also exceed 16. In one embodiment, the ratio between the element height H and the element width W can be less than 0.5 and can also be less than 0.25. A gas sensor element having an increased element height H (e.g., an increased aspect ratio) relative to the element width W according to many embodiments can have an increased gas sensor element surface area. Some embodiments provide that gas sensor elements with increased surface area can be arranged closer together in a reduced area across the substrate, reducing the footprint of the gas sensor. In some embodiments, the ratio between the element width and the spacing between elements can be less than 4. In some embodiments, the electrical characteristic response of a gas sensor element can depend, at least in part, on the gas sensor element surface area, including (but not limited to) the surface area of a nanoporous electrical conductor. In some embodiments, the nanoporous electrical conductor can increase the interfacial area between the sensing material and the gas such that the response of the gas sensor element to the corresponding gas can be increased. Some embodiments provide that a gas sensor comprising high aspect ratio nanoporous gas sensor elements has increased sensitivity and a reduced footprint.

[0111] A plan view of a gas sensor with different gas sensor elements according to an embodiment of the present invention is illustrated in FIG. 3. The gas sensor 99 comprises a plurality of gas sensor elements 10A, 10B, 10C that are different from each other. The plurality of gas sensor elements 10A-C in the gas sensor 99 can provide measurements of different gases and / or gas concentrations in a single gas sensor 99. For example, the first gas sensor element 10A can comprise different nanoparticles than the nanoparticles in the second gas sensor element 10B. The nanoparticles can be sensitive to different gases and / or gas concentrations.

[0112] A cross-sectional view of a gas sensor with different gas sensor elements obtained along cross-section line A of FIG. 3 according to an embodiment is shown in FIG. 4. The gas sensor 99 includes a plurality of gas sensor elements 10A, 10B, 10C that are different from each other. The plurality of gas sensor elements 10A-C can provide measurements of different gases and / or gas concentrations in a single gas sensor 99. The first gas sensor element 10A can include first nanoparticles 12A, and the second gas sensor element 10B, different from the first nanoparticles 12A, can include second nanoparticles 12B that are sensitive to different gases or gas concentrations. The first and second nanoparticles 12A, 12B are collectively referred to as nanoparticles 12. The third gas sensor element 10C can also include different nanoparticles 12 (not shown). The gas sensor element 10C can have a shape factor different from that of the first gas sensor element 10A. The different shape factors can be different lengths L (the length of the electrical connection between the first electrode 30A and the second electrode 30B to the gas sensor element 10 as shown in FIG. 3), different cross-sections (e.g., different element heights H, different element widths W, or different element shapes).

[0113] In FIG. 4, gas sensor elements 10A and 10B having an increased element height H (e.g., an increased aspect ratio) with respect to the element width W can have an increased gas sensor element surface area 15 and can be arranged closer together in a reduced area across the substrate 20 on which the gas sensor elements 10 are disposed, reducing the footprint of the gas sensor 99. The electrical characteristic response of the gas sensor element 10 can depend at least in part on the gas sensor element surface area 15, e.g., the surface area of a nanoporous electrical conductor. The nanoporous electrical conductor of the gas sensor element can improve the interfacial area between the sensing material and the gas, and the response of the gas sensor element to the corresponding gas is increased. FIGS. 3 and 4 illustrate specific gas sensor structural schemes and a plurality of different gas sensor element compositions, but any configuration and design can be utilized as appropriate according to the specific requirements of a given application.

[0114] In many embodiments, the microheater of a gas sensor can include individually controllable microheater segments. According to some embodiments, the individually controllable microheater segments can be individually controllable, (but not limited to) by including a sensor controller, to provide different temperatures simultaneously in each microheater segment. Some embodiments provide that each microheater segment can be associated with and / or in thermal contact with a different gas sensor element. In such embodiments, the plurality of microheater segments can simultaneously heat the corresponding gas sensor elements to different temperatures. According to many embodiments, gas sensor elements heated to different temperatures can be applied to detect different gases and / or gas concentrations through individual and separate microheater electrodes. Some embodiments provide that the substrate and / or the insulating layer can have a relatively high thermal resistance to allow different temperatures in different microheater segments. By providing differently controllable and different gas sensor elements, the gas sensor can simultaneously measure different gases and / or different gas concentrations and can comprise an electronic nose.

[0115] By reducing the occupied area of the gas sensor element, the total area of the microheater can be reduced according to many embodiments without degrading the temperature uniformity of the gas sensor element. The power draw of the microheater can increase with area. The reduction in the total area of the microheater results in a reduction in gas sensor power consumption and can facilitate the use of the gas sensor according to some embodiments in battery-powered electronic devices.

[0116] A plan view of individually controllable microheater sections in a gas sensor, according to an embodiment of the present invention, is illustrated in FIG. 5. The microheater 90 comprises individually controllable microheater sections 91 that are individually controllable (e.g., by a sensor controller 74 as shown in FIG. 1) to provide different temperatures simultaneously in each microheater section 91. Each microheater section 91 can be associated with or in thermal contact with a different gas sensor element 10, and the plurality of microheater sections 91 can simultaneously heat the corresponding gas sensor elements 10 to different temperatures, for example, to detect different gases or gas concentrations, through individual and separate microheater electrodes 92 (e.g., a first microheater electrode 92A, a second microheater electrode 92B, a third microheater electrode 92C, collectively, microheater electrodes 92). The substrate 20, the insulating layer 96, or both can have a relatively high thermal resistance to allow different temperatures in different microheater sections 91. By providing differently controllable and different gas sensor elements 10, the gas sensor 99 can simultaneously measure different gases or different gas concentrations and can comprise an electronic nose. Reducing the occupied area of the gas sensor elements 10 can reduce the total area of the microheater 90 without degrading the temperature uniformity of the gas sensor elements 10. Since the power draw of the microheater 90 increases with area, this results in a reduction in the power consumption of the gas sensor 99 and promotes the use of such a gas sensor 99 in battery-powered electronic devices. FIG. 5 illustrates a specific microheater incorporation in a gas sensor scheme, but any configuration and design can be utilized as appropriate according to the specific requirements of a given application.

[0117] In many embodiments, the gas sensor can be a microsensor having elements with sizes in the range of several nanometers to several microns to tens of microns. In some embodiments, the gas sensor element can have an element width W that ranges from about 1 micron to about 50 microns. In one embodiment, the gas sensor element can have an element width W that ranges from about 5 microns to about 20 microns. In some embodiments, the width W of the gas sensor element can be about 10 microns. Some embodiments provide that the gas sensor element can have an element height H that ranges from about 100 nanometers to about 20 microns. In some embodiments, the gas sensor element can have a height H that ranges from about 1 micron to about 10 microns. In one embodiment, the height H of the gas sensor element can be about 5 microns. In many embodiments, the gas sensor element can be separated across the substrate by a distance that ranges from about 1 micron to about 50 microns. Some embodiments provide that the gas sensor element can be separated across the substrate by a distance that ranges from about 5 microns to about 20 microns. In some embodiments, the gas sensor element can be separated across the substrate by a distance of about 15 microns. Many embodiments provide that the gas sensor electrode can have a thickness that ranges from about 10 nm to about 5 microns. In some embodiments, the gas sensor electrode can have a thickness of about 100 nm. In some embodiments, each gas sensor element can have a height H within the range of about 1 micron to about 20 microns and a width within the range of about 1 micron to about 50 microns.

[0118] The size and separation of gas sensor elements and gas sensor electrodes according to some embodiments may not be constructed using inkjet, drop casting, and / or screen printing techniques. Additionally, the thin film structure may have a reduced surface area and thus a reduced sensitivity. Many embodiments enable gas sensors with increased sensitivity and reduced footprint. Some embodiments provide that the gas sensor elements can be constructed with better control of the amount and structure of the sensing material, including (but not limited to) molten nanoparticles between the electrodes, such that electrical property measurements can be more consistent and repeatable. Improved process fidelity and reproducibility according to some embodiments lead to better control of the surface properties of the gas sensor elements, thereby reducing the variability of the electrical response of the manufactured gas sensor and reducing the need for calibration of the manufactured gas sensor.

[0119] Many embodiments provide that the gas sensor element of a gas sensor can have a geometric shape including (but not limited to) lines and straight lines, curves, or spirals. A single gas sensor element with a single first electrode and a single second electrode according to some embodiments can have multiple portions each corresponding to a different nanoporous electrical conductor. In some embodiments, multiple gas sensor elements can be interdigitated and / or different gas sensor elements can have different nanoporous electrical conductors that are interdigitated. The gas sensor element can have different shapes and / or cross-sections including (but not limited to) square, rectangular, cubic, circular, or cylindrical. In some embodiments, a gas sensor element having a linear shape factor including (but not limited to) a high aspect ratio shape factor and an element length L that far exceeds the element width W or the element height H can have a larger gas sensor element surface area at a reduced surface area. A gas sensor element according to an embodiment has a larger gas sensor element surface area as compared to a gas sensor material provided using drop casting, screen printing, or inkjet printing. A gas sensor element with a larger gas sensor element surface area according to some embodiments can increase the sensitivity of the elements of the gas sensor and reduce the size of the gas sensor, particularly with respect to a gas sensor comprising multiple gas sensor elements in an electronic nose.

[0120] Many embodiments provide that the nanoparticles of the gas sensor element can have diameters ranging from about 1 nm to about 1 micron. In some embodiments, the nanoparticles can have diameters ranging from about 10 nm to about 500 nm. In some embodiments, the nanoparticles can have diameters of about 100 nm or less than about 100 nm. In one embodiment, the nanoparticles have diameters ranging from about 1 nm to about 5 microns.

[0121] In many embodiments, the aggregates of nanoparticles in the nanoporous electrical conductor of the gas sensor element may not be the same and may have a size distribution. The nanoparticle size distribution according to some embodiments can include (but is not limited to) a distribution of diameters centered on a nominal diameter. Thus, a nanoparticle referred to as having a diameter of about 100 nm according to an embodiment can actually be a collection or aggregate of nanoparticles having a distribution of diameters with a substantially about 100 nm average (e.g., within manufacturing tolerances). Some embodiments provide that the gas sensor element can have a surface roughness of less than about 1 micron RMS. In certain embodiments, the gas sensor element can have a surface roughness of less than about 150 nm RMS, less than about 100 nm RMS, and / or less than about 50 nm RMS.

[0122] Many embodiments provide that the nanoparticles of the gas sensor can include, but are not limited to, metal nanoparticles, metal oxide nanoparticles, or doped metal oxide nanoparticles. Metal oxide nanoparticles according to certain embodiments can include, but are not limited to, SnO2, TiO2, ITO, CdSe, WO3, ZnO, In2O3, Cd:ZnO, CrO3, V2O5, and any combination thereof. In some embodiments, the metal oxide nanoparticles can be doped with Al, Pt, Pd, Au, Ag, Ti, Cu, Fe, Sb, Mo, Ce, Mn, Rh2O3, or carbon nanotubes (CNT) to improve the selectivity of the sensor. Such materials can be effectively used to detect target gases in various applications. In some embodiments, the aggregate of nanoparticles can include materials including, but not limited to, non-conductive materials, semi-conductive, and / or dielectric materials. According to embodiments, these materials can be sensitive to gases, can affect the response of the conductive material in the nanoporous electrical conductor, and / or can be useful for constructing the nanoporous electrical conductor. In some embodiments, the nanoparticle ink can be provided as a suspension in a liquid solvent including, but not limited to, an aqueous dispersant and / or an organic solvent. Examples of organic solvents include, but are not limited to, isopropanol, ethanol, toluene, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, diethylene glycol monomethyl ether, or triethylene glycol monomethyl ether. According to some embodiments, the nanoparticles can have a viscosity in the range of about 0.3 centipoise to about 300 centipoise. In some embodiments, the nanoparticles can comprise different nanoparticles made from different conductive, semi-conductive, or non-conductive materials and can be distributed isotropically or anisotropically within the gas sensor element.

[0123] Many embodiments provide that the substrate of the gas sensor can include, but is not limited to, glass, polymer, semiconductor, ceramic, quartz, metal, paper, and / or sapphire. Examples of polymers that can constitute the substrate can include, but are not limited to, Kapton (polyimide), PET, PMMA, Teflon® (PTFE), and ETFE. Examples of semiconductors can include, but are not limited to, Si, SiO2, Si3N4, SiC, GaAs, GaInP, InP, and any combination of these materials. In some embodiments, the substrate for the gas sensor can be a printed circuit board (PCB) substrate that includes, but is not limited to, FR2, FR4, or liquid crystal polymer (LCP) material. Some embodiments provide that the substrate can be rigid, flexible, and / or substantially planar. In some embodiments, the substrate can be found in the display, integrated circuit, electronic device assembly, or circuit board industries. In some embodiments, the substrate may contain CMOS and / or MEMS devices, integrated circuits, microprocessors, microcontrollers, angular measurement circuitry, RF circuits, and transceivers.

[0124] A gas sensor having gas sensor elements with various sizes according to an embodiment of the present invention is illustrated in FIG. 6. The gas sensor 99 can be a microsensor having elements with sizes in the nanometer, micron, or tens of micron range. For example, the gas sensor element 10 can have an element width W ranging from about 1 micron to about 50 microns, or from about 5 microns to about 20 microns. In FIG. 6, the width W of one gas sensor element 10 is about 10 microns. The gas sensor element 10 can have an element height H ranging from about 100 nanometers to about 20 microns, or from about 1 micron to about 10 microns. In FIG. 6, the height H of one gas sensor element 10 is about 5 microns. The gas sensor element 10 can be separated across the substrate 20 by a distance ranging from about 1 micron to about 50 microns, or from about 5 microns to about 20 microns. In FIG. 6, the distance separation between gas sensor elements is about 15 microns. The gas sensor electrode 30 can have a thickness ranging from about 10 nm to about 5 microns. In FIG. 6, the thickness of the gas sensor electrode is about 100 nm. The gas sensor element 10 can be fabricated using nanoparticles 94. The nanoparticles 94 can have a diameter D range, for example, from about 1 nm to about 1 micron, or from about 10 nm to about 500 nm. In FIG. 6, the nanoparticles 94 have a diameter of about 100 nm or less than about 100 nm, for example, from about 1 nm to about 5 microns. FIG. 6 illustrates specific gas sensor structural dimensions and gas sensor element compositions, but any configuration and design can be appropriately utilized according to the specific requirements of a given application.

[0125] In many embodiments, the gas sensor can have a substrate with segments of different thicknesses. Substrates with thinner segments, according to some embodiments, can provide faster temperature changes and better thermal control and temperature distribution for the gas sensor element in response to the microheater. A gas sensor with a substrate having segments of different thicknesses, according to an embodiment, is illustrated in FIG. 7. The substrate 20 can have a thinner substrate 21 at the center of the substrate 20 than at the edges of the substrate 20. Such a thinned substrate 21 can provide faster temperature changes and better thermal control and temperature distribution for the gas sensor element 10 in response to the microheater 90, for example, by reducing heat loss through the substrate 20. In some embodiments, the thinner substrate 21 can comprise a SiO2 or Si3N4 film with a thickness of about 10 nm to about 1 micron and can be suspended across an opening in the substrate 20. In some embodiments, the film may contain openings to further reduce heat loss.

[0126] Many embodiments provide that the gas sensor can be constructed using a microfabrication machine (discussed further below). A plan view of a gas sensor disposed on or across a substrate, according to an embodiment of the present invention, is illustrated in FIG. 8. In FIG. 8, the gas sensor 99 comprises a plurality of gas sensor elements 10 (e.g., first and second gas sensor elements 10A, 10B). Each gas sensor element has first and second electrodes 30A, 30B disposed across a microheater electrode 92 on the substrate 20 (insulating layer 96 is not shown). The first and second electrodes 30A, 30B provide conductivity sensing for the corresponding gas sensor element 10 and conduct current through the nanoporous electrical conductor of each gas sensor element 10.

[0127] As shown in FIG. 8, additional current or voltage injection electrodes 31A, 31B can be incorporated. The force electrodes 31A, 31B are connected to the gas sensor element 10 and can provide a four-point probe measurement configuration. This can improve the long-term stability of the device by reducing or eliminating the influence of contact resistance between the sensing elements (e.g., the first and second electrodes 30A, 30B) on the measurement. FIGS. 7 and 8 illustrate specific gas sensor structures and compositions, but any configuration and design can be appropriately utilized according to the specific requirements of a given application.

[0128] Systems of micro-molding machines that can be utilized in a micro-molding process according to various embodiments of the present invention are further discussed below. (Micro-molding machine)

[0129] Many embodiments provide a micro-molding machine that can be used in a micro-molding process. According to some embodiments, the micro-molding machine can process high-resolution electrical conductors with a high aspect ratio. The electrical conductors can be integrated into electrical devices including (but not limited to) gas sensors, inductors, and antennas. Many embodiments provide that the micro-molding machine has various features embedded within at least one surface of the micro-molding machine. In some embodiments, the micro-molding machine can act as a stamp for imprinting features embedded on a substrate. In some embodiments, the micro-molding machine has at least one ink supply source for supplying ink during the micro-molding process.

[0130] Many embodiments provide that the micro - molding machine includes at least a stamp. The stamp can have, according to some embodiments, a first channel disposed on the surface of the stamp and a second channel disposed on the surface of the stamp. In some embodiments, a first inlet port can be connected to the first channel, and a second inlet port separate from the first inlet port can be connected to the second channel. Some embodiments provide a first ink including a nanoparticle ink source for supplying (but not limited to) a first ink to the first inlet port, and a second ink including a nanoparticle ink source separate from the first ink source for supplying (but not limited to) a second ink to the second inlet port. In some embodiments, the micro - molding machine includes pumps and / or dispensers for pumping and / or dispensing the first ink through the first inlet port and the first channel, and pumping and / or dispensing the second ink through the second inlet port and the second channel. Many embodiments provide that the micro - molding machine can have a contact mechanism for contacting the surface of the stamp with a substrate. In some embodiments, the channels in the stamp are positioned relative to features on the substrate, ensuring that the features are disposed at specific locations on the substrate within a defined positional tolerance including (but not limited to) 1 micron or 10 microns. In some embodiments, the channels in the stamp can be positioned relative to features on the substrate using fiducial markers on the stamp and the substrate optically. In some embodiments, the channels in the stamp can be positioned relative to features on the substrate by mechanical contact.

[0131] In some embodiments, the first ink can be an ink comprising nanoparticles, the second ink can be an ink comprising nanoparticles, and the nanoparticle composition in the first ink can be the same as or different from the nanoparticle composition in the second ink. Some embodiments provide that the first channel can have a first shape factor and the second channel can have a second shape factor that is the same as or different from the first shape factor. In many embodiments, the micro-molding machine can include an outlet port that is connected to the first channel or the second channel. A pump and / or dispenser according to some embodiments can provide a negative air pressure or vacuum below atmospheric pressure to the outlet port.

[0132] Some embodiments provide that a gas sensor can be constructed using a micro-molding machine. A plan view of a micro-molding machine according to an embodiment of the present invention is illustrated in FIG. 9A. A cross-sectional view of the micro-molding machine obtained by cutting across section line A in FIG. 9A is illustrated in FIG. 9B. A cross-sectional view of the micro-molding stamp obtained by cutting across section line B in FIG. 9A is illustrated in FIG. 9C. A plan view of a micro-molding machine with a separate ink reservoir according to an embodiment of the present invention is illustrated in FIG. 9D.

[0133] The micro-mold machine 98 can include a micro-mold stamp 40 having a mold layer 44 with a support side 46 and a channel side 48. A support layer 42 is disposed in contact with the support side 46. The support layer 42 is more rigid than the mold layer 44, can provide dimensional stability to the mold layer 44, and can enable improved resolution regarding the structure formed by the micro-mold stamp 40. The mold layer 44 can include at least one channel 50 (e.g., a micro-channel or channels 50 as shown) disposed on the channel side 48 within the mold layer 44. An inlet port 52 is connected to the channel 50, and an outlet port 54 is connected to the channel 50. The channel 50 has a height in a direction from the channel side 48 away towards the support side 46 of the mold layer 44 (corresponding to the gas sensor element height H). The channel height can exceed the width of the channel 50 on the channel side 48 (corresponding to the gas sensor element width W). In some embodiments, the inlet and outlet ports 52 and / or 54 can extend to the channel side 48 surface of the mold layer 44. The inlet port 52 provides a path for the nanoparticle ink 56 to enter the channel 50, and the outlet port 54 provides a path for the nanoparticle ink to be drawn in and out of the channel 50. The mold layer 44 can include an elastomeric material such as polydimethylsiloxane, polyurethane, room temperature vulcanizing silicone rubber, or photocurable rubber that is cast and cured on a defined master, e.g., a master structure micromachined on a silicon wafer or a polymer structure processed on a substrate such as a silicon wafer using, e.g., photolithography. The support layer 42 can include a material more rigid than the mold layer 44, such as glass, silicon, polymethylmethacrylate, polycarbonate, or quartz, and can be thinner than the mold layer 44. In some embodiments, the mold layer 44 can be reinforced by incorporation of nanoparticles into the elastomeric material or by inclusion of a fiber mesh made of, e.g., but not limited to, materials including glass, steel, carbon, or nylon. The support layer 42 can include a material more rigid than the mold layer 44, such as, but not limited to, glass, and can be thinner than the mold layer 44.

[0134] In FIGS. 9A - 9D, the micro - molding machine 98 includes a micro - mold stamp 40 having a first channel 50A disposed on the surface of the micro - mold stamp 40 and a second channel 50B disposed on the surface of the micro - mold stamp 40. (The first channel 50A and the second channel 50B are collectively the channel 50.) In some embodiments, the channels 50 have a common substantially the same form factor (as shown in FIGS. 9A, 9D). In some embodiments, the first channel 50A has a first form factor and the second channel 50B has a second form factor different from the first form factor (as shown in FIG. 9B). A first inlet port 52A is connected to the first channel 50A and a second inlet port 52B is connected to the second channel 50B.

[0135] In some embodiments, each channel 50 has a separate and individual inlet port 52 (e.g., a first inlet port 52A and a second inlet port 52B) and a separate and individual outlet port 54 (e.g., a first outlet port 54A and a second outlet port 54B). In some embodiments, the individual inlet and outlet ports 52, 54 to each channel 50 can be positioned within the stamp such that the minimum distance between any pair of ports exceeds a predetermined distance ranging from about 100 microns to about 1 mm. In some embodiments, multiple channels 50 share an inlet port 52, an outlet port 54, or both. A common inlet port 52 provides structural simplicity and manufacturability when the channels 50 connected to the common inlet port 52 share a common nanoparticle 12 material. A common outlet port 54 provides structural simplicity and manufacturability for drawing nanoparticle 12 material from the channels 50 connected to the common outlet port 54. In some embodiments, the channels connected to the common inlet port 52 and outlet port 54 are used to deposit nanoparticle ink for gas - sensor elements that are part of a plurality of separate gas sensors constructed on a common substrate 20 using a single micro - mold stamp 40.

[0136] In FIG. 9A, the same nanoparticles are supplied to both the first inlet port 52A and the second inlet port 52B and can be supplied to both the first channel 50A and the second channel 50B. The first inlet port 52A is fed from a nanoparticle ink (not shown) source (ink reservoir 58), and the second inlet port 52B is fed from the same nanoparticle ink source (ink reservoir 58).

[0137] In FIG. 9D, different nanoparticles (e.g., the first nanoparticle 12A and the second nanoparticle 12B, not shown) are separately supplied to the first inlet port 52A and the second inlet port 52B and can be separately supplied to the first channel 50A and the second channel 50B. The first inlet port 52A is fed from a nanoparticle ink source (the first ink reservoir 58A), and the second inlet port 52B is fed from a different nanoparticle ink source (the second ink reservoir 58B). (The first ink reservoir 58A and the second ink reservoir 58B are collectively the ink reservoir 58. The inlet port 52 and the outlet port 54 can include the ink reservoir 58.)

[0138] In FIG. 9C, the pump 70 or dispenser pumps and / or dispenses the first nanoparticle ink through the first inlet port 52A and the first channel 50A, and pumps and / or dispenses the second nanoparticle ink through the second inlet port 52B and the second channel 50B. In some embodiments, the first and second nanoparticle inks can be the same nanoparticle ink or different nanoparticle inks. The pump or dispenser 70 can provide pressure for filling the nanoparticle ink into the channel 50 at a higher speed and at a reduced cost than applying capillary action alone. The contact mechanism (e.g., the optomechatronic motion control platform 62 shown in FIG. 9B that employs a mechanical position microcontroller and a position sensor, e.g., an optical sensor) can bring the surface of the micro mold stamp 40 (e.g., the channel side 48) into contact with the surface 22 (e.g., the substrate 20 or a layer on the substrate 20 such as an insulating layer). Thus, the micro molding machine 98 can provide different nanoparticle inks to substantially the same channel 50, provide substantially the same nanoparticle ink to different channels 50 (e.g., channels 50 having different form factors), or provide different nanoparticle inks to different channels 50.

[0139] The inlet port 52 can be fed from a source of nanoparticle ink 56. A pump and / or dispenser 70 pumps or dispenses the nanoparticle ink 56 through the inlet port 52 and the channel 50. The pump or dispenser 70 can provide a pressure for filling the channel 50 with nanoparticle ink at a higher speed and at a reduced cost than is possible with capillary action alone. In FIGS. 11A-11D, the pump or dispenser 70 provides the nanoparticle ink 56 (e.g., comprising nanoparticles 12 in a dispersant or solvent 57) from the pump reservoir 72 and the ink reservoir 58 under pressure to the inlet port 52 of the micro mold stamp 40, provides a vacuum (or partial vacuum or reduced pressure) to the outlet port 54, and draws the nanoparticle ink 56 through the channel 50. The micro mold stamp 40 can comprise a nanoparticle ink reservoir 58 for controlling the volume and flow rate of the nanoparticle ink 56. The inlet port 52 and the outlet port 54 can also serve as an integrated ink reservoir 58. In some embodiments, the pressure driving the nanoparticle ink 56 through the channel 50 can be the capillary pressure caused by the force between the nanoparticle ink 56 and the surface area of the microchannel 50 in contact with the nanoparticle ink 56.

[0140] FIGS. 9A-9D illustrate specific microfabrication machine structures and compositions, but any configuration and design can be utilized as appropriate according to the specific requirements of a given application. Systems and methods of a microfabrication process that can be utilized in fabricating electrical devices according to various embodiments of the present invention are further discussed below. (Fabrication of Gas Sensors Using the Microfabrication Process)

[0141] Many embodiments provide a micro - molding process for electrical components and / or devices. Examples of electrical components and / or devices include, but are not limited to, gas sensor elements, antennas, inductors. The micro - molding process according to some embodiments implements a micro - molding machine. Many embodiments provide that the micro - molding process may include, but is not limited to, the following steps, namely, · Providing a substrate having a substrate surface; · Providing a stamp having a mold layer with a support side and a channel side, and a support layer disposed in contact with the support side; · Providing a first ink, including but not limited to, nanoparticle ink, and a second ink, including but not limited to, nanoparticle ink; · Disposing the mold layer in contact with the substrate surface; · Pumping or dispensing a first nanoparticle ink into a first channel through a first inlet port; · Pumping or dispensing a second nanoparticle ink into a second channel through a second inlet port; · Curing the first nanoparticle ink in the first channel; · Curing the second nanoparticle ink in the second channel; · Removing the stamp and forming a self - standing component on the substrate surface; and may include.

[0142] In some embodiments, the mold layer can include a first channel having a first shape factor disposed on the channel side, a first inlet port connected to the first channel, and a first outlet port connected to the first channel. In some embodiments, the mold layer can include a second channel having a second shape factor disposed on the channel side, a second inlet port connected to the second channel, and a second outlet port connected to the second channel. A mold stamp according to an embodiment can be fabricated using materials including, but not limited to, polydimethylsiloxane, polymethylmethacrylate, and polyurethane. Some embodiments provide that the first shape factor of the first channel and the second shape factor of the second channel can have the same or different shape factors. In many embodiments, the support layer can be more rigid than the mold layer. Some embodiments provide that the channel can have a height, or both, in a direction from the channel side to the mold layer that exceeds the width of the channel on the channel side. In some embodiments, features within the stamp are positioned relative to features on the substrate to ensure that micro-molding features are placed at specific locations on the substrate within a defined positional tolerance including, but not limited to, 1 micron or 10 microns. In one embodiment, features within the stamp can be positioned relative to features on the substrate using visual fiducial markers on the stamp and the substrate.

[0143] One embodiment provides that the first nanoparticle ink and the second nanoparticle ink can be the same or different nanoparticle inks. In some embodiments, curing the nanoparticle ink can form a nanoporous molten nanoparticle electrical conductor. The nanoporous molten nanoparticle electrical conductor according to some embodiments can have an electrical conductivity that varies in response to the ambient gas in contact with the nanoporous molten nanoparticle electrical conductor. The step of curing the nanoparticle ink according to some embodiments can be accelerated by heating the nanoparticle ink and / or by exposing the nanoparticle ink to electromagnetic radiation. In some embodiments, the nanoparticles can be sintered by heating the nanoparticles and / or by exposing the nanoparticles to electromagnetic radiation.

[0144] Many embodiments provide that when the inlet pressure exceeds the outlet pressure, the step of providing the inlet pressure to the inlet port and the outlet pressure to the outlet port can pump the nanoparticle ink into the channel through the inlet port. In some embodiments, the step of pumping and / or dispensing the nanoparticle ink can flow the nanoparticle ink through the channel, and the flow of the nanoparticle ink can be driven at least in part by the capillary pressure in the channel. In one embodiment, the step of pumping and / or dispensing the nanoparticle ink can flow the nanoparticle ink through the channel, and the flow of the nanoparticle ink can be driven by applying pressure to the inlet port and / or applying a vacuum to the outlet port.

[0145] A process for fabricating components using a micro-molding process according to an embodiment of the present invention is illustrated in FIG. 10. The fabrication process is initiated by providing a substrate for the component (100). A micro-molding stamp can be used to place the component (105). The mold layer of the micro-molding stamp can be placed in contact (e.g., conformally) with the substrate surface of the substrate (115). A nanoparticle ink comprising nanoparticles in a liquid or gaseous solvent or dispersant can be provided (110). The nanoparticle ink comprising nanoparticles can be pumped into the channels through an inlet port (120). As the nanoparticles move through the channels, the solvent in the nanoparticle ink can diffuse into the mold layer, such that the nanoparticles become closely packed within the channels. Complete wetting of the channels by the ink can be important for achieving the desired shape and facilitating rapid extraction of the solvent, which can be achieved by careful adjustment of the solvent and the surface energy of the stamp. The process can be accelerated by curing (125). According to some embodiments, the curing process includes the step of exposing the nanoparticle ink to heat and / or electromagnetic radiation (but not limited to). Examples of electromagnetic radiation include (but not limited to) xenon flash, infrared radiation, ultraviolet radiation, or laser radiation. During the curing process, the solvent of the nanoparticle ink can be expelled from the nanoparticle ink and / or the mold layer. In some embodiments, the expelled solvent can be (at least partially) absorbed by the mold layer of the micro-molding stamp. The micro-molding stamp can be removed to form a self-standing gas sensor element on the substrate surface of the substrate (130). The self-standing gas sensor element can be formed without being formed within the substrate or having a support structure and / or walls. In some embodiments, the nanoparticles can be sintered and / or melted to form the gas sensor element (135). According to an embodiment, the step of sintering and / or melting the nanoparticles can be accomplished by exposing the nanoparticles to heat, UV radiation, laser radiation, or electromagnetic radiation.In some embodiments, the sintering process can be carried out in a protective atmosphere, including (but not limited to) nitrogen, helium, argon, hydrogen, carbon dioxide. Many embodiments provide that when multiple gas sensor elements have different form factors and / or comprise different nanoparticles, the gas sensor can be constructed within a single layer and in a single series of steps. FIG. 10 illustrates specific steps of a microfabrication process, although any steps and methods can be utilized as appropriate according to the specific requirements of a given application.

[0146] Sequential cross-sectional views of a high aspect ratio gas sensor during a fabrication process according to an embodiment are illustrated in FIGS. 11A-11D. In FIGS. 11A-11D, a gas sensor element 10 can be constructed by providing a substrate 20, a micro mold stamp 40, and a nanoparticle ink 56 comprising nanoparticles 12 in a provided liquid or gaseous solvent or dispersant 57. The mold layer 44 of the micro mold stamp 40 is arranged in contact (e.g., conformally) with a surface 22 (e.g., the surface of the substrate 20 or an insulating layer 96) as shown in FIG. 11A. As illustrated in FIG. 11B, the nanoparticle ink 56 comprising nanoparticles 12 can be pumped into the channel 50 through the inlet port 52, for example, by a pump 70 from a pump reservoir 72. The pumping can be provided by providing at least partially a pressure difference between the inlet port 52 and the outlet port 54. As the nanoparticles 12 move through the channel 50, the solvent 57 in the nanoparticle ink 56 diffuses into the mold layer 44, drawing more ink from the inlet and outlet reservoirs 58, and thus the nanoparticles 12 become tightly packed within the channel 50. The process continues until the average pore size in the structure becomes about the pore size of the nanoparticles 12 in the ink and all the solvent is extracted, ultimately leading to a complete molding of the channel shape. Complete wetting of the channel by the ink can be important for achieving the desired shape and facilitating rapid extraction of the solvent, which can be achieved by careful adjustment of the surface energies of the solvent and the stamp used.

[0147] In FIG. 11C, the curing process can be accelerated and / or enabled, for example, by exposing the nanoparticle ink 56 and / or the mold layer 44 to heat and / or electromagnetic radiation 60 including (but not limited to) xenon flash, ultraviolet radiation, or laser radiation, to drive out at least partially the solvent 57 that can be absorbed by the mold layer 44 of the micro mold stamp 40. The micro mold stamp 40 is then removed to form a gas sensor element 10 (optionally having a high aspect ratio) on the surface 22. The nanoparticles 12 can then be sintered or melted by exposing the nanoparticles 12 to heat, UV radiation, or laser radiation to form the gas sensor element 10. The sintering process can be carried out in a protective atmosphere including (but not limited to) nitrogen, helium, argon, hydrogen, carbon dioxide. The gas sensor element 10 can be free-standing, for example, not formed within a substrate or having a support structure or walls (excluding the lower surface 22). FIGS. 11A - 11D illustrate specific steps of a micro molding process for fabricating a gas sensor, but any steps and methods can be utilized as appropriate depending on the specific requirements of a given application.

[0148] A system of high aspect ratio antennas with high aspect ratio conductors that can be utilized in the design of antennas according to various embodiments of the present invention is further discussed below. (Antenna)

[0149] An antenna couples voltage and current to an electromagnetic field, enabling communication or power transfer between spatially separated electronic devices. A wide variety of antennas can be used for different applications, such as radio, television, WiFi, radar, and wireless power transfer (WPT). Antennas come in different sizes and configurations and can operate at various frequencies, e.g., from 3 kHz to 300 GHz. Different bands of the electromagnetic spectrum are reserved for different applications, such as radio, television, and cellular phone communication (smartphones). A complete antenna system operates by wirelessly coupling electrical energy from the voltage and current flowing in one set of electrical conductors (the "transmitter") to the voltage and current induced in another set of electrical conductors (the "receiver") via an electromagnetic field or inductive coupling.

[0150] A far-field (radiating) antenna system tends to generate electromagnetic waves that propagate at long distances from the transmitter, regardless of the presence of a receiving antenna. In contrast, a near-field (non-radiating) antenna system generates a strong evanescent field very close to the transmitter and is suitable for inductively coupling to nearby receivers but does not radiate power into propagating free-space electromagnetic modes. For an antenna to operate efficiently in the far-field (radiating) region, the physical extent of the antenna is typically on the order of the wavelength of the signal being transmitted, or even much larger for directive antennas such as dish antennas. Far-field antennas can range from a few microns to hundreds of meters in extent, depending on the frequency and antenna type. Near-field antennas can be dramatically smaller than the wavelength but tend to operate effectively only over distances on the same order of magnitude as the antenna size and also tend to require low-loss conductors, careful resonance tuning, and precise alignment between the transmitter and receiver. Many different antenna designs are used, such as loop antennas, dipole antennas, microstrip antennas, monopole antennas, array antennas, and conical antennas.

[0151] A variety of near-field antennas are used for different applications, such as short-range wireless communication (NFC) between electronic devices such as smartphones, radio frequency identification (RFID) tags and readers, wireless power transfer, and data transfer in stacked ICs, and include many different sizes and configurations operating at various frequencies, for example, from about 1 kHz to about 1 THz. The near-field antenna may be configured to receive and / or transmit data or power, and the near-field device may be powered directly by an external power source such as a battery or by power captured from the near field as in the case of RFID.

[0152] Different bands of the electromagnetic spectrum are reserved for different applications, such as radio, television, and cellular phone communication (smartphones). Near-field RFID systems such as 13.56 MHz RFID systems typically operate within the low frequency range (LF, 125 KHz - 134 KHz) or high frequency range (HF, 3 MHz - 30 MHz) bands. However, operation of near-field RFID within the ultra-high frequency range (UHF, 300 MHz - 3 GHz) band is also considered possible. (Near-field coil antenna)

[0153] An antenna system can comprise a single transmission antenna and a single reception antenna. Modern antenna systems can contain a number of transmitters and receivers, each utilizing at least one individual antenna. Some antennas can function as both transmitters and receivers in such a system. A near-field antenna system can rely on inductive coupling between two antennas, such as coil-type antennas, to transmit electrical signals and / or power. When an electrical signal is passed through one coil, an electromagnetic field can be generated within its near-field region, which can induce a voltage or current in another coil that is proportional to the mutual inductance between the two coils. The mutual inductance can be maximized when the coils are oriented concentrically and as close to each other as possible, and when each coil itself has maximum inductance, for example, by maximizing the number of windings within its occupied area. Each turn of the trace around the internal space is known as a winding. To further improve the distance over which a near-field antenna can operate, it can be useful to tune each coil for resonant operation at the operating frequency, minimize resistive losses, and enable high-quality factor (high-Q) operation. This can require precise control over the dimensions of the coils.

[0154] Near-field antennas do not rely on radiating electromagnetic energy into the far field and can therefore be operated with very low transmission losses, being limited in principle only by their own resistive losses. This makes near-field antennas convenient for applications such as RFID, short-range communication, and wireless power transfer. Or, more generally, for any application where it is not possible or desirable to establish a direct electrical connection to a device for data or power transmission, such as stacked integrated circuits (ICs).

[0155] Portable electronic devices are preferably small and lightweight. As a result, coil antennas and inductors in such portable electronic devices should desirably be small, but with closely spaced low-resistance conductors to maintain performance. For many applications in microelectronics, it may be desirable to produce a compact antenna coil with the highest possible inductance (as many turns as practicable) and low series resistance for any given antenna footprint and conductor length. Techniques for fabricating small electrical conductors within or on substrates such as printed circuit boards and integrated circuits include subtractive techniques and additive techniques. Subtractive techniques can include photochemical machining, etching, laser cutting, and machining. Additive techniques can include mask physical vapor deposition (e.g., vacuum deposition) of conductive ink or paste, electroplating, 3D printing, inkjet printing, and screen printing. However, inkjet printing and screen printing have limited resolution and limited reproducibility on the submillimeter scale and are associated with poorly controlled cross-sectional shapes. Photochemical machining, which consists of patterning an etching mask followed by etching as used in PCB manufacturing, can result in isotropic undercutting of masked conductor edges. Undercutting limits the achievable form of conductors and the gaps separating them and can reduce conductor resolution. Electroplating onto a patterned metal seed layer can improve the conductivity of traces, but is also plagued by reduced conductor resolution because metal deposition proceeds in a nominally isotropic manner and again limits the minimum gap between conductor traces. Finally, conductive polymers as an alternative to metals are limited in conductivity and can be several orders of magnitude lower than those of, for example, copper or silver.

[0156] In previous research, Ko et. al. described a method for patterning electrical conductors by coating a substrate with a nanoparticle solution and imprinting the coating using a structured polydimethylsiloxane mold. (See, e.g., Ko, et. al., Nano Letters, 2007, vol. 7, No. 7 pp. 1869-1877, the disclosure of which is incorporated herein by reference in its entirety). Makihata and Pisano described printing using silver nanoparticle ink. (See, e.g., Makihata et al., The International Journal of Advanced Manufacturing Technology, 2019, 103, 1709-1719, the disclosure of which is incorporated herein by reference in its entirety).

[0157] Many embodiments provide a design and fabrication method for a compact high-Q antenna structure and / or an inductor coil to improve the performance of various electrical circuits and wireless devices. Some embodiments provide a compact antenna coil with high inductance and low series resistance by fabricating a coil of a highly conductive material with closely spaced high aspect ratio traces.

[0158] High aspect ratio coils can be applied in the fabrication of high Q low loss air core inductors according to many embodiments. High Q low loss air core inductors play an important role in high frequency electronic circuit design. Many embodiments implement a high aspect ratio coil structure as an inductor in fields including (but not limited to) switched mode power supplies, radio frequency (RF) bandpass, highpass, and lowpass filters, low loss transformers, inductive angle and position sensors, and LC or RLC resonators. Printed inductors and / or coils according to some embodiments can be integrated as discrete components, as part of a larger distributed element network, or as a microstrip containing multiple passive components. In such embodiments, the high accuracy of the printed inductor / coil can provide benefits including (but not limited to) more accurate tuning of the resonant frequency, smaller footprint, sub-quarter wavelength filtering, and higher power coupling efficiency.

[0159] A system of high aspect ratio antennas with high aspect ratio conductors that can be utilized in the design of antennas according to various embodiments of the present invention is further discussed below. (High aspect ratio antenna)

[0160] A common type of near field antenna is an inductive coil comprising a spiral or helical arrangement of a conductive electrical material. Such electrical conductors can be wires with various cross-sectional profiles, such as cylindrical wires, rectangular wires, or planar electrical conductors. Many embodiments implement a high aspect ratio electrical conductor as the electrical conductor. These wires and / or traces according to embodiments can be arranged in configurations including (but not limited to) planar rectangles, circles, or hexagonal spirals on a substrate to form a coil. The coil can be about 1×1 μm 2 and about 1×1 m 2It can have the outer dimensions. In some embodiments, the coil can contain an internal space not occupied by a coiled conductor such as an air-core inductor. In some embodiments, the internal space of the coil may be occupied by a magnetic core to increase the inductance. The coil can extend in a direction normal to the substrate according to an embodiment such that the conductor has an increased aspect ratio. In some embodiments, some coils can be stacked to increase the inductance of the coil. In some embodiments, a plurality of coaxially positioned coils can be installed around the same axis. These coils can be located in the same plane or substrate, or installed in a subsequent plane or substrate along the same axis. The design of the coil can be symmetric or asymmetric.

[0161] The quality and bandwidth of signal transmission between two near-field antennas depend on their mutual inductance, the magnitude of the current passed through the transmitting antenna, and the frequency at which the coil is driven. The mutual inductance can be determined by the physical separation and orientation between the two antennas and their individual self-inductances. The radius of the antenna should be adjusted to the distance at which the signal is expected to be received. For example, a pair of coil antennas with an outer dimension of about 10 mm can provide the best transmission when the separation distance is about 12 mm. The mutual inductance increases with the number of turns in each of the coils. The antenna should have a low electrical resistance. Higher resistance can result in attenuation of the field and signal strength, and undesired power dissipation and heating in this device.

[0162] Many embodiments provide high aspect ratio electrical conductors arranged in various configurations for high performance inductors and antennas, including (but not limited to) near field antennas. In some embodiments, antennas with high aspect ratio conductors can be processed as free-standing structures formed or deposited on a substrate. High aspect ratio conductors according to some embodiments can be constructed from nanoparticle inks cured within channels disposed within a stamp applied on a substrate surface. Some embodiments provide that these processes enable antennas and inductors to be fabricated with dimensions suitable for small and portable electronic devices. In certain embodiments, the antennas and conductors have dimensions in the range of about 1 μm to about 100 μm.

[0163] Many embodiments provide that the substrate of a high aspect ratio antenna can be any suitable substrate, including (but not limited to) glass, polymer, Kapton (polyimide), PET, PMMA, Teflon® (PTFE), ETFE, ceramic, low temperature co-fired ceramic (LTCC), semiconductor, Si, SiO2, Si3N4, SiC, GaAs, GaInP, InP, quartz, metal, paper, and / or sapphire. In some embodiments, the substrate can be a printed circuit board (PCB) substrate, including (but not limited to) FR2 or FR4. In some embodiments, the substrate can be rigid, flexible, or planar. Some embodiments provide that the substrate can be found in the display, integrated circuit, electronic device assembly, or circuit board industries. In some embodiments, the substrate may contain CMOS and / or MEMS devices, integrated circuits, microprocessors, microcontrollers, angle measurement circuitry, RF circuits, and transceivers.

[0164] In many embodiments, the high aspect ratio antenna can be fabricated using particles including, but not limited to, conductive particles, metal nanoparticles, non-conductive (dielectric) particles, or semiconductive particles. Examples of nanoparticles include, but are not limited to, silver, copper, gold, nickel nanoparticles, or any combination thereof. In some embodiments, the nanoparticles can be sintered. In one embodiment, the nanoparticles can be coated by a conductor. In some embodiments, the nanoparticles can be coated by a thin metal coating by electroplating. Electroplating can provide a metal coating over the surface, but can also deposit a coating material on the substrate surface that can reduce the spatial resolution of the structures formed on the substrate surface. In some embodiments, the nanoparticles are not electroplated. Examples of semiconductive particles include, but are not limited to, metal oxides. In some embodiments, the particles can be provided as a suspension in a liquid solvent including, but not limited to, an aqueous dispersant, an organic solvent, isopropanol, ethanol, toluene, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, diethylene glycol monomethyl ether, or triethylene glycol monomethyl ether. According to one embodiment, the nanoparticles can have a diameter in the range of about 1 nm to about 5 μm. Some embodiments provide that a suitable ink can have a viscosity in the range of about 0.3 centipoise to about 3,000 centipoise. In some embodiments, the nanoparticles can include different nanoparticles made from different conductive and / or non-conductive materials. In some embodiments, the nanoparticles can be distributed isotropically or anisotropically within the antenna.

[0165] Many embodiments provide high aspect ratio antenna structures. In some embodiments, the antenna can form a coil on a substrate. A plan view of a high aspect ratio antenna according to an embodiment of the present invention is illustrated in FIG. 12A. The high aspect ratio antenna structure 10 includes a substrate 20 having a substrate surface 22. An antenna 30 is disposed on the substrate surface 22. The antenna 30 is a planar rectangle, circle, or hexagonal spiral on the substrate surface 22 and can form a coil.

[0166] A cross-sectional view of a high aspect ratio antenna obtained along section line A of FIG. 12A according to an embodiment of the present invention is illustrated in FIG. 12B. The high aspect ratio antenna structure 10 includes a substrate 20 having a substrate surface 22. An antenna 30 is disposed on the substrate surface 22. The antenna 30 can have a rectangular cross-section or any other desirable cross-section including, but not limited to, triangular, quadrilateral, or those with curved surfaces. The antenna 30 can be electrically connected to a circuit (not shown) that operates or responds to the antenna 30. The antenna 30 can be made from molten nanoparticles 12. The electrical conductor of the antenna 30 has a base 32 having a conductor width W in contact with the substrate surface 22 and a conductor height H in a direction extending away from the substrate surface 22. The antenna 30 can stand on its own on the substrate surface 22 without any support other than the support from the base 32 on the substrate 20. The conductor height H can exceed the conductor width W. In some embodiments, the antenna 30 can have an exposed conductor surface 35 of the molten nanoparticles 12 at at least one point along the conductor. In some embodiments, the conductor surface 35 can be coated with a conductive material disposed on the molten nanoparticles 12. The exposed conductor surface 35 can optionally be the outer edge or surface of the antenna 30 excluding the base 32. In various embodiments, the electrical conductor of the antenna 30 can vary in size, height, width, aspect ratio, composition, and density over the length of the electrical conductor on the substrate 20.

[0167] In many embodiments, the base of the antenna disposed on the substrate surface can have a conductor width W that is less than 50 microns. Some embodiments provide a conductor width W that is less than 25 microns, less than 10 microns, less than 5 microns, or less than 2 microns. The conductor height H of the antenna extending away from the substrate surface according to some embodiments can be greater than 5 microns. In one embodiment, the conductor height H can be greater than 10 microns, greater than 20 microns, greater than 50 microns, or greater than 100 microns. In many embodiments, the antenna has an aspect ratio (the ratio of the conductor height H to the conductor width W) greater than 1. In some embodiments, the aspect ratio of the antenna can be greater than 2.8, greater than 5, greater than 10, or greater than 20. One embodiment provides that an antenna with an aspect ratio greater than 2.8 can have a conductor width W of about 2.5 microns and a conductor height of about 7 microns.

[0168] Many embodiments provide a coil antenna incorporating a high aspect ratio electrical conductor. In some embodiments, the coil antenna has a conductor length L that extends from one end of the coil antenna to the other end of the coil antenna. The coil antenna according to some embodiments has a separation distance D between the turns of the antenna coil. In many embodiments, the high aspect ratio antenna structure can provide a greater number of turns N of the antenna in a reduced area and / or volume, enabling improved sensitivity to electromagnetic radiation within a frequency range. Examples of frequency ranges include (but are not limited to) frequencies less than 867 MHz. Such sensitivity can be useful in the small form factor of portable electronic devices. A plan view of a coil antenna according to an embodiment of the present invention is illustrated in FIG. 13A. In FIG. 13A, a high aspect ratio coil antenna 10 includes a coil antenna 30 disposed on a substrate surface 22 of a substrate 20. The antenna 30 has a first portion 36 on the substrate 20 that is adjacent to a second portion 38 on the substrate 20. The first portion 36 and the second portion 38 are separated by a distance D across the substrate surface 22.

[0169] In FIG. 13A, the coil length L of the antenna 30 extends from the first end 30A of the antenna to the second end 30B of the antenna with a small separation distance D between the windings of the antenna 30 (corresponding to the first and second portions 36, 38 of the antenna 30). Thus, the high aspect ratio antenna structure 10 can provide a greater number of turns N of the antenna 30 across the substrate 20 in a reduced area or volume, enabling improved sensitivity to electromagnetic radiation within a desired frequency range.

[0170] A cross-sectional view of a high aspect ratio coil antenna obtained along the cross-section line A of FIG. 13A according to an embodiment of the present invention is illustrated in FIG. 13B. The coil antenna 30 is disposed on the substrate surface 22 of the substrate 20. The first portion 36 and the second portion 38 are spaced apart by a distance D across the substrate surface 22. The distance D can be less than or equal to the conductor height H. In some embodiments, the first portion 36 is separated from the second portion 38 by a distance D of less than 50 microns. In some embodiments, the distance D between the first portion 36 and the second portion 38 is less than 25 microns, less than 20 microns, less than 15 microns, less than 10 microns, and less than 5 microns. Many embodiments provide that the windings of the antenna 30 are closely spaced together, enabling a large conductor length L of the antenna 30 in a small area across the substrate 20. In some embodiments, the antenna 30 (e.g., a coil) has a single turn. In some embodiments, the coil has a plurality of turns with one or more adjacent first and second portions 36 and 38 as shown in FIG. 13A. In one embodiment, the antenna 30 has straight segments that are joined together at discontinuous corners. In some embodiments, the corners of the electrical conductors in the antenna 30 are orthogonal (90-degree) angles. In some embodiments, the corners are non-orthogonal. Examples of non-orthogonal angles include (but are not limited to) 60 degrees, 120 degrees, or 150 degrees. Some embodiments provide that the antenna 30 has straight segments. According to some embodiments, the antenna 30 has curved segments or is completely curved.

[0171] A plan view of an antenna with antenna length L according to an embodiment of the present invention is shown in FIG. 14A. Antenna 30 has an antenna length L from a first end of the antenna to a second end of the antenna and is disposed on substrate surface 22 of substrate 20. A cross-sectional view of the antenna obtained along cross-sectional line A of FIG. 14A according to an embodiment of the present invention is shown in FIG. 14B. Antenna 30 has an antenna base 32, an antenna width W, and an antenna height H.

[0172] Some embodiments provide that a coil antenna may have sections incorporating a thermal strain reducer to prevent buckling of the sections during (rapid) temperature changes. Rapid temperature changes can occur during sintering or operation of the antenna. According to some embodiments, the thermal strain reducer can divide these sections into a plurality of shorter sections to prevent buckling. A coil antenna incorporating a thermal strain reducer according to an embodiment of the present invention is shown in FIG. 15. Thermal strain reducer 37 is incorporated within sections of the coil antenna and divides these sections into a plurality of shorter sections to prevent buckling of the sections during (rapid) temperature changes. FIGS. 12-15 illustrate specific high aspect ratio antenna structure schemes and compositions, but any configuration and design can be utilized as appropriate according to the specific requirements of a given application.

[0173] Systems and methods for fabricating a high aspect ratio antenna with high aspect ratio conductors using a microfabrication process that can be utilized in the design and / or fabrication of antennas according to various embodiments of the present invention are further discussed below. (Fabrication of High Aspect Ratio Antennas Using a Microfabrication Process)

[0174] Many embodiments provide that a high aspect ratio microstrip antenna can be used for high frequency (above about 100 MHz) applications, including (but not limited to) millimeter wave antennas and microwave antennas. Typically, a microstrip antenna is manufactured by using photolithography to create an etching mask and subsequently etching the metal. This is a multi-step process that can limit the options for substrates on which such circuits can be processed. Typically, the metal etching step needs to be performed early in the production process to avoid damaging or degrading complex structures or devices such as ICs present on the substrate. Metal etching can also limit the achievable aspect ratio of the antenna conductors because the conductor thickness needs to be smaller than the feature spacing. Also, common metal etching techniques can be limited by the isotropic nature of the etching process, which can limit the form accuracy achievable for high aspect ratio structures. On the other hand, evaporating metal on a masked substrate in a vacuum and then performing a lift-off step to remove the mask would waste most of the material that cannot be recovered, while evaporating a thin film of metal and then performing electrochemical deposition of the metal can limit the feature spacing and fidelity.

[0175] Many embodiments provide that a high aspect ratio antenna structure can include a plurality of antennas, including (but not limited to) coil antennas disposed on a substrate. According to some embodiments, the plurality of antennas can form a phased array antenna.

[0176] Some embodiments provide that a high aspect ratio antenna can be constructed using a micro mold stamp. A plan view of a micro mold stamp according to an embodiment of the present invention is illustrated in FIG. 16A. A cross-sectional view of the micro mold stamp taken across cross-sectional line A of FIG. 16A is illustrated in FIG. 16B. A cross-sectional view of the micro mold stamp taken across cross-sectional line B of FIG. 16A is illustrated in FIG. 16C. The micro mold stamp 40 can include a mold layer 44 having a support side 46 and a channel side 48. A support layer 42 is disposed in contact with the support side 46. The support layer 42 is more rigid than the mold layer 44 and can provide dimensional stability to the mold layer 44 and enable improved resolution regarding the structure formed by the micro mold stamp 40. The mold layer 44 can include at least one channel 50 disposed on the channel side 48 within the mold layer 44. An inlet port 52 is connected to the channel 50, and an outlet port 54 is connected to the channel 50. The channel 50 has a height in a direction away from the channel side 48 and toward the support side 46 of the mold layer 44 that exceeds the width of the channel 50 on the channel side 48 (corresponding to the conductor width W) (corresponding to the conductor height H). In some embodiments, the inlet and outlet ports 52 and / or 54 can extend to the channel side 48 surface of the mold layer 44. The inlet port 52 provides a path for the nanoparticle ink 56 to enter the channel 50, and the outlet port 54 provides a path for the nanoparticle ink to be drawn into and out of the channel 50. The mold layer 44 can include an elastomeric material including, but not limited to, polydimethylsiloxane, which is cast and cured on a photolithographically defined master including, but not limited to, a silicon master, a quartz master, or a glass master. In some embodiments, the mold layer 44 can be reinforced by incorporation of nanoparticles into the elastomeric material or by inclusion of a fiber mesh made of, including but not limited to, glass, steel, carbon, or nylon. The support layer 42 can include a material more rigid than the mold layer 44, including, but not limited to, glass, and can be thinner than the mold layer 44.

[0177] In FIG. 16C, the pump and / or dispenser 70 provides the nanoparticle ink from the pump reservoir 72 under pressure to the inlet port 52 of the micro mold stamp 40, provides a vacuum (or partial vacuum or reduced pressure) to the outlet port 54, and can draw the nanoparticle ink 56 therethrough into the channel 50. The micro mold stamp 40 can include a nanoparticle ink reservoir 58 for controlling the volume and flow rate of the nanoparticle ink 56. The inlet port 52 and the outlet port 54 can also serve as an integrated ink reservoir 58. In some embodiments, the pressure driving the ink through the channel can be a capillary pressure caused by the force between the nanoparticle ink 56 and the surface area of the microchannel 50 in contact with the ink.

[0178] A process for fabricating a high aspect ratio antenna according to an embodiment of the present invention is illustrated in FIG. 10. The fabrication process begins by providing a substrate for the high aspect ratio antenna (100). A micro-molding stamp can be used to place the antenna (105). The mold layer of the micro-mold stamp can be placed in contact (e.g., conformally) with the substrate surface of the substrate (115). A nanoparticle ink comprising nanoparticles in a liquid or gaseous solvent or dispersant can be provided (110). The nanoparticle ink comprising nanoparticles can be pumped into the channels through an inlet port (120). As the nanoparticles move through the channels, the solvent in the nanoparticle ink can diffuse into the mold layer, and thus the nanoparticles become tightly packed within the channels. The process can be accelerated by curing (125). According to some embodiments, the curing process includes exposing the nanoparticle ink to heat and / or electromagnetic radiation (but not limited to). Examples of electromagnetic radiation include (but not limited to) xenon flash, infrared radiation, ultraviolet radiation, or laser radiation. During the curing process, the solvent of the nanoparticle ink can be expelled from the nanoparticle ink and / or the mold layer. In some embodiments, the expelled solvent can be (at least partially) absorbed by the mold layer of the micro-mold stamp. In one embodiment, the expelled solvent can diffuse into the environment surrounding the stamp through the mold layer. Examples of the environment surrounding the stamp include (but not limited to) air, vacuum, or an inert gas including (but not limited to) nitrogen and argon. The micro-mold stamp can be removed to form a self-standing antenna with high aspect ratio conductors on the substrate surface of the substrate (130). The self-standing antenna can then be sintered by exposing the nanoparticles to heat, UV radiation, or laser radiation (135). Many embodiments provide that the antenna can be constructed within a single layer and in a single series of steps. According to some embodiments, the fabrication process of the antenna avoids repeated deposition and patterning steps.

[0179] Cross-sectional views of a high aspect ratio antenna during a fabrication process, according to an embodiment, are illustrated in FIGS. 17A-17D. A high aspect ratio antenna structure, according to some embodiments, can be constructed by providing a substrate 20 and a micro mold stamp 40, as shown in FIG. 17A. The mold layer 44 of the micro mold stamp is disposed in contact (e.g., conformally) with the substrate surface 22 of the substrate 20, as shown in FIG. 17A. A nanoparticle ink 56 comprising nanoparticles 12 in a liquid or gaseous solvent or dispersant 57 can be pumped, for example, by a pump, through an inlet port 52 into a channel 50, as shown in FIG. 17B. As the nanoparticles 12 move through the channel 50, the solvent in the nanoparticle ink 56 diffuses into the mold layer 44, and thus the nanoparticles 12 become tightly packed within the channel 50. In FIG. 17C, the process can be accelerated and / or enabled by exposure of the nanoparticle ink 56 and / or the mold layer 44 to heat and / or electromagnetic radiation 60 (e.g., xenon flash, infrared radiation, ultraviolet radiation, or laser radiation). The process can expel the solvent 57, which can be at least partially absorbed by the mold layer 44 of the micro mold stamp 40 or diffuse into the environment surrounding the stamp through the mold layer. The micro mold stamp 40 can then be removed to form a free-standing antenna with a high aspect ratio conductor 30 on the substrate surface 22 of the substrate 20 in FIG. 17D. The free-standing antenna 30 can then be sintered by exposing the nanoparticles 12 to heat, UV radiation, or laser radiation. The antenna 30 can be constructed in a single layer and in a single series of steps.

[0180] FIGS. 16A-16C and FIGS. 17A-17D illustrate specific steps of a microfabrication process for a high aspect ratio antenna, although any steps and methods can be utilized as appropriate according to the specific requirements of a given application. Systems and methods for integrating a high aspect ratio antenna with circuit components, according to various embodiments of the present invention, are further discussed below. (Integration of High Aspect Ratio Antenna)

[0181] Many embodiments provide that a high aspect ratio antenna can be integrated into an electronic circuit that includes, but is not limited to, a tuned antenna system. In some embodiments, components including, but not limited to, circuits, integrated circuits (ICs), resistors, and capacitors can be incorporated into the antenna system. In some embodiments, the additional components can be placed inside and / or outside of the coil. In one embodiment, the components can be placed in different circuit planes.

[0182] In order to receive signals from a coil antenna, both ends of the spiral conductor trace need to be electrically connected to an external circuit, which may require an out-of-plane circuit connection to one or both ends of the antenna spiral. Many embodiments provide an antenna system design to enable excitation and / or reception signals from the coil antenna. Some embodiments incorporate conductive traces that are fabricated either above or below the coil. According to certain embodiments, the conductive trace can connect the innermost coil to a coplanar region outside the coil. In some embodiments, the conductive trace can connect the outermost coil to a coplanar region within the coil. Many embodiments provide that the electrical connection can be made either above or below the trace or wire forming the coil. In some embodiments, the electrical connection can be made by wire bonding or by depositing a separate conductor above or below the coil. In some embodiments, the electrical connection can be made with an electrical insulation (dielectric) layer to avoid short circuits between the coil loops of a high aspect ratio antenna. Many embodiments provide that an antenna with a high aspect ratio conductor can be disposed on at least one component including, but not limited to, an electrical conductor, a dielectric, other structures, other high aspect ratio structures, layers, MEMS devices, COMS devices, or structured layers. Some embodiments provide that the antenna can be electrically connected to a circuit including, but not limited to, an integrated circuit controller, a circuit that responds to signals provided through the high aspect ratio antenna.

[0183] In many embodiments, the high aspect ratio antenna can comprise an antenna portion disposed structurally and an antenna portion disposed structurally differently. In some embodiments, the two ends of the high aspect ratio antenna are connected to two different portions of the antenna. In some embodiments, one portion of the antenna can be disposed across an electrical conductor and the other portion of the antenna can be disposed across an electrically insulating dielectric. Such a structure can enable the electrical conductor to be electrically connected to one end of the antenna but not to the other end of the antenna. In some embodiments, independent electrical connections can be made at different ends of the antenna. In some embodiments, independent electrical connections can be made between the antenna and an electrical circuit such as an integrated circuit inside or outside the coil antenna. An independent electrical connection according to an embodiment can avoid an undesired electrical connection to other portions of the antenna.

[0184] In some embodiments, the high aspect ratio antenna can be coated with a material including (but not limited to) a sealant, a dielectric sealant, or a metal coating. Examples of sealants can include (but not limited to) polymers including curable polymers, epoxies, polydimethylsiloxanes, polyurethanes, low temperature co-fired ceramic (LTCC) sheets. According to an embodiment, the coating can protect the antenna from environmental contaminants. In some embodiments, the sealant coating layer can form a more mechanically robust structure of the antenna. In some embodiments, the sealant layer can enhance the electromagnetic properties of the antenna, such as by improving its conductivity. According to an embodiment, the sealant layer can planarize the antenna or form a conformal coating over the antenna.

[0185] An antenna system according to an embodiment of the present invention is illustrated in FIG. 18. In some embodiments, the high aspect ratio antenna 30 can be installed on the substrate surface 22 of the substrate 20. In some embodiments, the antenna 30 with the high aspect ratio conductor can be arranged across the structure 26 on the substrate 20. In one embodiment, the antenna 30 can be arranged on the conductive substrate contact 24 that provides an electrical connection to the antenna 30. The substrate contact 24 can extend across the substrate 20 or cover only a selected area. The first and second portions 36, 38 of the antenna 30 can be arranged across different structures on the substrate 20, such as the electrical conductor 24 and the electrical insulating dielectric 26. Such a structure can allow the electrical conductor to be electrically connected to the first portion 36 of the antenna 30 but not to the second portion 38 of the antenna 30, and thus an independent electrical connection can be made to the electrical circuit 28 inside or outside the coil antenna 30 without unwanted electrical connections to the first end 30A (shown in FIG. 13A) of the coil antenna 30 and the second end 30B (shown in FIG. 13A) of the coil antenna 30 or to other parts of the antenna 30. Thus, the high aspect ratio antenna 30 can include a first antenna portion 36 arranged on a first structure (e.g., the substrate contact 24), and a second antenna portion 38 is arranged on a second structure different from the first structure (e.g., the dielectric 26). The antenna 30 can be coated with a sealant 80 for protection.

[0186] In many embodiments, the high aspect ratio antenna can be a multi-layer antenna. In some embodiments, each antenna layer can be separated from an adjacent layer by an insulator and can be connected through electrical vias. Some embodiments provide that the conductive path between the outer and inner regions of the coil antenna can be created by a second coil of opposite chirality. In one embodiment, the second coil of opposite chirality can be placed concentrically with the first coil, above or below the first coil. Some embodiments provide that the first and second coil antennas can be electrically insulated from each other by an insulator, except at the connection points in the innermost or outermost extent of the coils. In some embodiments, the vias can electrically connect an electrical conductor in one antenna layer to an electrical conductor in another antenna layer. In such embodiments, the inductance of the multi-layer coil structure can be significantly improved compared to a single-layer coil while providing coplanar points for connecting the coil to an external circuit.

[0187] A multi-layer high aspect ratio antenna, according to an embodiment of the present invention, is illustrated in the exploded perspective view of FIG. 19. The conductive path between the outer and inner regions of the coil is created by a second coil of opposite chirality, which is placed above (as shown in FIG. 19) or below the first coil and is concentric with the first coil, and can be electrically insulated therefrom by an insulator 21 over all areas except for a single connection point in the innermost or outermost extent of the coil. The vias, shown by the dashed lines in FIG. 19, can electrically connect an electrical conductor in one antenna layer to an electrical conductor in another antenna layer. Thus, the inductance of the multi-layer coil structure can be significantly improved compared to a single-layer coil while providing coplanar points for connecting the coil to an external circuit. FIGS. 18 and 19 illustrate implementing specific elements and components in the high aspect ratio antenna, but any configuration and design can be utilized as appropriate according to the specific requirements of a given application. Doctrine of equivalents

[0188] As can be inferred from the above discussion, the concepts referred to above can be implemented in various arrangements according to embodiments of the present invention. Thus, although the present invention has been described in a certain specific aspect, many additional modifications and variations will be apparent to those skilled in the art. Therefore, it is to be understood that the present invention may be practiced otherwise than as specifically described. Accordingly, the embodiments of the present invention are to be considered in all respects as illustrative and not restrictive.

Claims

【Claim 1】 The invention described in this specification.

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