Abstract:
Embodiments of the present invention relate to graphene-based microphone diaphragms. In one embodiment, a acoustic wave sensor comprises a diaphragm comprised of a graphene-based composition, wherein the diaphragm has a first side at least partially covered with a reflective material. An emitter fiber is positioned proximate to the diaphragm, wherein the emitter fiber transmits light towards the first side. A collector fiber is positioned proximate to the diaphragm, wherein the collector fiber captures at least a portion of light reflected by the first side, wherein the collector fiber is in communication with a detector. A converter is in communication with the detector and converts a signal received by the detector to a digital signal for processing. The portion of light that is captured as a result of diaphragm distortion is different than the portion of light captured in the absence of diaphragm distortion. The graphene-based composition includes graphene sheets.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to U.S. Provisional Application No. 62/140,496 filed Mar. 31, 2015, which is hereby incorporated herein by reference. 
     
    
     BACKGROUND 
       [0002]    The present invention relates generally to microphones and specifically to graphene-based microphone diaphragms. Microphones typically are acoustic-to-electric transducers or sensors that convert sound into an electrical signal. Microphones typically include a pressure sensitive diaphragm that can convert sound to mechanical motion, which can subsequently be converted to an electrical signal. Microphone varieties are typically categorized by the transducer type that is incorporated therein, for example, condenser, dynamic, ribbon, carbon, piezoelectric, fiber optic, liquid, pressure-gradient, and microelectric-mechanical system (MEMS). In certain microphones, the diaphragm can be positioned between a fixed internal volume of air and the environment, which allows the microphone to respond uniformly to pressure from a plurality of directions. In other microphones, the diaphragm can be at least partially open on both of its sides, which can result in pressure differences between the two sides that gives the microphones directional characteristics. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0003]      FIG. 1  depicts a sensor, generally  100 , in accordance with an embodiment of the present invention. 
           [0004]      FIG. 2  depicts fabrication steps, in accordance with an embodiment of the present invention. 
           [0005]      FIG. 3  depicts additional fabrication steps, in accordance with an embodiment of the present invention. 
           [0006]      FIG. 4  depicts additional fabrication steps, in accordance with an embodiment of the present invention. 
           [0007]      FIG. 5  depicts additional fabrication steps, in accordance with an embodiment of the present invention. 
           [0008]      FIG. 6  depicts additional fabrication steps, in accordance with an embodiment of the present invention. 
           [0009]      FIG. 7  depicts additional fabrication steps, in accordance with an embodiment of the present invention. 
           [0010]      FIG. 8  depicts additional fabrication steps, in accordance with an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0011]    The descriptions of the various embodiments of the present invention have been presented for purposes of illustration but are not intended to be exhaustive or limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The terminology used herein was chosen to best explain the principles of the embodiments, the practical application or technical improvement over technologies found in the marketplace, or to enable others of ordinary skill in the art to understand the embodiments disclosed herein. 
         [0012]    Certain terminology may be employed in the following description for convenience rather than for any limiting purpose. For example, the terms “forward” and “rearward,” “front” and “rear,” “right” and “left,” “upper” and “lower,” and “top” and “bottom” designate directions in the drawings to which reference is made, with the terms “inward,” “inner,” “interior,” or “inboard” and “outward,” “outer,” “exterior,” or “outboard” referring, respectively, to directions toward and away from the center of the referenced element, the terms “radial” or “horizontal” and “axial” or “vertical” referring, respectively, to directions or planes which are perpendicular, in the case of radial or horizontal, or parallel, in the case of axial or vertical, to the longitudinal central axis of the referenced element, and the terms “downstream” and “upstream” referring, respectively, to directions in and opposite that of fluid flow. Terminology of similar import other than the words specifically mentioned above likewise is to be considered as being used for purposes of convenience rather than in any limiting sense. 
         [0013]    In the figures, elements having an alphanumeric designation may be referenced herein collectively or in the alternative, as will be apparent from context, by the numeric portion of the designation only. Further, the constituent parts of various elements in the figures may be designated with separate reference numerals which shall be understood to refer to that constituent part of the element and not the element as a whole. General references, along with references to spaces, surfaces, dimensions, and extents, may be designated with arrows. Angles may be designated as “included” as measured relative to surfaces or axes of an element and as defining a space bounded internally within such element therebetween, or otherwise without such designation as being measured relative to surfaces or axes of an element and as defining a space bounded externally by or outside of such element therebetween. Generally, the measures of the angles stated are as determined relative to a common axis, which axis may be transposed in the figures for purposes of convenience in projecting the vertex of an angle defined between the axis and a surface which otherwise does not extend to the axis. The term “axis” may refer to a line or to a transverse plane through such line as will be apparent from context. 
         [0014]    Microphones typically are acoustic-to-electric transducers or sensors that convert sound into an electrical signal. Microphones typically include a pressure sensitive diaphragm that can convert sound to mechanical motion, which can subsequently be converted to an electrical signal. Microphone varieties are typically categorized by the transducer type that is incorporated therein, for example, condenser, dynamic, ribbon, carbon, piezoelectric, fiber optic, liquid, pressure-gradient, and micro-electro-mechanical-system (MEMS) microphones. In certain microphones, the diaphragm can be positioned between a fixed internal volume of air and the environment, which allows the microphone to respond uniformly to pressure from a plurality of directions. In other microphones, the diaphragm can be positioned in a manner to be at least partially open on both of its sides, which can result in the formation of pressure differences between the two sides of the diaphragm and results in directional detection characteristics. 
         [0015]    Embodiments of the present invention seek to provide graphene-based microphone diaphragms. As used herein, the term microphone and sensor are interchangeable and both denote an electrical device that detects acoustic pressure waves. Other embodiments of the present invention seek to provide microphone diaphragms that comprise a graphene-based composition having graphene sheets. Still other embodiments of the present invention seek to provide printed microphone diaphragms. Additional embodiments of the present invention seek to provide microphone diaphragms that are coated with a reflective material or a metal, which includes, but is not limited to, silver, aluminum, lead, gold, platinum, rhodium, copper, magnesium, brass, bronze, titanium, zirconium, nickel, tantalum, tin, and/or an alloy thereof. 
         [0016]      FIG. 1  depicts a sensor, generally  100 , in accordance with an embodiment of the present invention. Sensor  100  is a fiber optic microphone. Sensor  100  may comprise a housing (not shown) that includes reflective diaphragm  130 , which can transmitted by photo-emitter  110  to photo-collectors  120 . Photo-emitter  110  and/or photo-collectors  120  can be optical fibers. Photo-emitter  110  can be a laser. Sensor  100  can detect pressure wave  140 . Upon a change in atmospheric pressure, pressure wave  140  can cause reflective diaphragm  130  to distort, which can result in a change in the distance between reflective diaphragm  130  and photo-collectors  120  and a subsequent modulation of the quantity of light that reflective diaphragm  130  reflects towards photo-collectors  120 , wherein the amount of light received by photo-collectors  120  is proportional to the force of pressure wave  140 . 
         [0017]    Sensor  100  has a detectable frequency range that can be increased or decreased by decreasing or increasing, respectively, the thickness (i.e. cross-section) of at least a portion of reflective diaphragm  130 . As the thickness of reflective diaphragm  130  decreases, the quantity of force that is required by pressure wave  140  to distort reflective diaphragm  130  decreases. As the quantity of force with which pressure wave  140  impacts reflective diaphragm  130  decreases, the thickness of at least a portion of reflective diaphragm  130  can be decreased to facilitate the distortion of reflective diaphragm  130  and detection of pressure wave  140 . Photo-emitter  110  can be a fiber optic thread having a photo-emitting first end facing reflective diaphragm  130  and a second end in communication with a photo-source, such as component  115 . Photo-emitter  110  can be in communication with component  115 , which is an electrical device that can transmit generated light via photo-emitter  110 . Photo-collectors  120  can be a fiber optic thread having a photo-collecting first end facing reflective diaphragm  130  and a second end in communication with a photo-detector, such as component  125 . Photo-collectors  120  can be in communication with component  125 , which is an electrical device that can quantify light received via photo-collectors  120 . 
         [0018]    Although not shown, components  115  and  125  can be a single component. Components  115  and/or  125  can be in communication with a computing device that controls the operation of components  115  and/or  125 . Reflective diaphragm  130  can be positioned at least partially within a housing (not shown) in a manner to facilitate the detection of acoustic pressure (i.e. sound), for example, pressure wave  140 . Photo-emitter  110  and photo-collectors  120  can be positioned proximate to reflective diaphragm  130  in a manner to maximize any distortion of reflective diaphragm  130  that results from the impact of pressure wave  140 . Photo-emitter  110  can be positioned in a manner to be in approximate alignment with the central axis of the housing and/or reflective diaphragm  130 . Photo-collectors  120  can be positioned proximate to photo-emitter  110 . Photo-collectors  120  can be positioned radially around photo-emitter  110 . Photo-collectors  120  can be positioned asymmetrically or symmetrically relative to photo-emitter  110 . Although not shown, sensor  100  can comprise one or more copies of photo emitter  110  and/or photo collector  120 . 
         [0019]    Sensor  100  may have a sensitivity of up to 1100 nm/kPa and/or have an ability to detect acoustic signals having a noise density as low as 60 μPa/√Hz at 10 kHz. The distance of photo-emitter  110  and photo-detectors  120  relative to reflective diaphragm  130  can be the same or different. Reflective diaphragm  130  can be positioned proximate to photo-emitter  110  and/or photo-detectors  120  at a distance of about 50 μm to about 100 μm, about 100 μm to about 150 μm, about 150 μm to about 200 μm, about 200 μm to about 250 μm, about 250 μm to about 300 μm, about 300 μm to about 350 μm, about 350 μm to about 400 μm, about 400 μm to about 450 μm, about 450 μm to about 500 μm, about 500 μm to about 550 μm, about 550 μm to about 600 μm, about 600 μm to about 650 μm, about 650 μm to about 700 μm, about 700 μm to about 750 μm, about 750 μm to about 800 μm, about 800 μm to about 850 μm, about 850 μm to about 900 μm, about 900 μm to about 950 μm, or about 950 μm to about 1000 μm. In other embodiments, sensor  100  can be any microphone that comprises a diaphragm, including, but not limited to, condenser, dynamic, ribbon, carbon, piezoelectric, fiber optic, laser, liquid, or MEMS microphones. 
         [0020]    A discussion of a fabrication method is provided below followed by a discussion of applicable methods and materials.  FIGS. 2-4  are disclosed herein to facilitate a discussion of the fabrication of reflective diaphragm  130 , in accordance with an embodiment of the present invention. Layer  210  can be formed on at least a portion of the surface of substrate  200 . Layer  210  can be comprised of the composition (discussed above). Layer  300  can be formed on at least a portion of the surface of layer  210  (discussed below). Layer  300  may comprise one or more openings having a diameter  700 . Diameter  710  can be about 0.25 inch to about 0.5 inch, about 0.5 inch to about 0.75 inch, or about 0.75 inch to about 1.0 inch, The opening can have a diameter that is a sub-value of any of the aforementioned diameter ranges. Substrate  200  can be subsequently removed from layer  210 , which results in the structure of  FIG. 4  (a top view of the aforementioned resulting structure). Excess material can be removed from layers  210  and/or  300  to generate a substantially two-dimensional final shape as disclosed in  FIG. 5 . For example, the final shape and/or the one or more openings can be substantially circular, triangular, rectangular, equilateral, trapezoidal, rho or polygonal. Excess material can be removed from layers  210  and/or  300  to generate an intermediate structure that can undergo additional fabrication steps. 
         [0021]      FIGS. 6-8  depict additional fabrication steps, in accordance with an embodiment of the present invention. Specifically,  FIGS. 6-8  illustrate alternative fabrication embodiments for diaphragm  130 . Alternatively, subsequent to the removal of layer  200 , layer  600  can be applied to the surface of layer  300  opposite layer  210  to generate the structure of  FIG. 6 . Layer  600  can be applied using any method disclosed in the references. Layer  600  can have a thickness of about 11 μm to about 3 cm. Applicable thicknesses can include any value included in the above overall range. Applicable thicknesses can have any value range included in the above overall range. Applicable thicknesses can include any values and/or value ranges included therein. Layer  600  can comprise any material disclosed in the references (discussed above). Layer  600  can comprise PET, polyethylene, polypropylene, polyvinyl chloride, nylon, a metal, an alloy, brass, aluminum, copper, gold, silver, steal, tungsten, wood, cellulose-based materials, glass, ceramics, paper, acrylonitrile butadiene styrene, polylactic acid, polycarbonate, high impact polystyrene, high density polyethylene, and/or a photopolymer. 
         [0022]      FIG. 7  illustrates a top view of at least a portion of the structure of  FIG. 6 . Layer  600  can have an inner diameter that is approximately equal to, less than, or greater than diameter  710 . Although depicted as a ring, layer  600  can be any shape that complements the one or more openings of layer  300 . Layer  600  can be a supporting ring structure. Layer  600  can be utilized for post process handling. Layer  600  can be printed, applied, or formed to the desired final shape (discussed above). Layer  600  can be applied by three-dimensional printing. Layer  600  can be applied as a sheet having one or more openings, wherein excess portions of the sheet can be subsequently removed. Width  715  can be about 0.5 mm to about 1.0 mm, about 1.0 mm to about 1.5 mm, about 1.5 mm to about 2 mm, about 2 mm to about 2.5 mm, about 2.5 mm to about 3.0 mm, about 3.0 mm to about 3.5 mm, about 3.5 mm to about 4.0 mm, about 4.0 mm to about 4.5 mm, and/or about 4.5 mm to about 5.0 mm. Alternatively, width  715  can be about 2 mm to about 3 cm. Width  715  can be any range of values included in the above ranges. Excess material can be removed from layers  300  and/or  210  to generate structure  800 . Structure  800  can be substantially circular, oblong, triangular, rectangular, equilateral, trapezoidal, rhombi, or polygonal. 
         [0023]    Applicable materials and methods are discussed below, in accordance with an embodiment of the present invention. Layer  210  can comprise a graphene-based composition (“the composition”). The composition can include graphene sheets. The graphene sheets and/or the composition can be formed utilizing the materials and/or methods that are disclosed in European patent application no. EP20120849213 to Redmond et al., European patent application no. EP20120849443 to Redmond et al., PCT publication no. WO2013074710 Al to Redmond et al., U.S. patent application Ser. No. 13/284,841, to Scheffer et al., U.S. patent application Ser. No. 12/848,152 to Scheffer et al., U.S. patent application Ser. No. 12/753,870 to Scheffer et al., U.S. patent application Ser. No. 13/260,372 to Varma et al., and U.S. patent application Ser. No. 13/140,834 to Scheffer et al. (“the references”) (herein incorporated by reference in their entirety). Substrate  200  and/or layer  300  can comprise one or more substrates that are disclosed in the references. Substrate  200  and/or  300  can be formed using one or more methods disclosed in the references. Layers  210  and/or  600  can be formed using a method disclosed in the references. 
         [0024]    Reflective diaphragm  130  can be formed in any applicable manner disclosed in the references. For example, layer  210  can be applied to the surface of substrate  200  at a thickness of about 0.5 μm to about 5.0 μm, 0.5 μm to about 0.75 μm, about 0.75 μm to about 1.0 μm, about 1.0 μm to about 1.25 μm, about 1.25 μm to about 1.5 μm, about 1.5 μm to about 1.75 μm, about 1.75 μm to about 2.0 μm, about 2.0 μm to about 2.25 μm, about 2.25 μm to about 2.5 μm, about 2.5 μm to about 2.75 μm, about 2.75 μm to about 3.0 μm, about 3.0 μm to about 3.25 μm, about 3.25 μm to about 3.5 μm, about 3.5 μm to about 3.75 μm, about 3.75 μm to about 4.0 μm, about 4.0 μm to about 4.25 μm, about 4.25 μm to about 4.5 μm, about 4.5 μm to about 4.75 μm, about 4.75 μm to about 5.0 μm, about 5.0 μm to about 10.0 μm, about 10.0 μm to about 15.0 μm, about 15.0 μm to about 20.0 μm, about 20.0 μm to about 25.0 μm, or about 25.0 μm to about 30.0 μm. Applicable thickness values for the composition can include subvalues that are included in the aforementioned thickness ranges. 
         [0025]    The applied composition can be cured at about 80° C. to about 85° C., about 85° C. to about 90° C., about 90° C. to about 95° C., about 95° C. to about 100° C., about 100° C. to about 105° C., about 105° C. to about 110° C., about 110° C. to about 115° C., about 115° C. to about 120° C., about 120° C. to about 125° C., about 125° C. to about 130° C., about 130° C. to about 135° C., about 135° C. to about 140° C., about 140° C. to about 145° C., about 145° C. to about 150° C., about 150° C. to about 155° C., about 155° C. to about 160° C., about 160° C. to about 165° C., about 165° C. to about 170° C., about 170° C. to about 175° C., about 175° C. to about 180° C., about 180° C. to about 185° C., about 185° C. to about 190° C., about 190° C. to about 195° C., about 195° C. to about 200° C. Applicable curing temperatures can include subvalues that are included in the aforementioned curing ranges. 
         [0026]    The applied composition can be cured for about 0.5 minutes to about 1.0 minutes, about 1.5 minutes to about 2.0 minutes, about 3.0 minutes to about 3.5 minutes, about 3.5 minutes to about 4.0 minutes, about 4.0 minutes to about 4.5 minutes, about4.5 minutes to about 5.0 minutes, about 5.0 minutes to about 5.5 minutes, about 5.5 minutes to about 6.0 minutes, about 6.0 minutes to about 6.5 minutes, about 6.5 minutes to about 7.0 minutes, about 7.0 minutes to about 7.5 minutes, about 7.5 minutes to about 8.0 minutes, about 8.0 minutes to about 8.5 minutes, about8.5 minutes to about 9.0 minutes, about 9.0 minutes to about 9.5 minutes, or about 9.5 minutes to about 10.0 minutes. Applicable curing times can include subvalues that are included in the aforementioned curing time ranges. 
         [0027]    Substrate  200  and/or layer  210  can comprise flexible and/or stretchable materials, silicones and other elastomers and other polymeric materials, metals (such as aluminum, copper, steel, stainless steel, and other metals), adhesives, heat-sealable materials (such as cellulose, biaxially oriented polypropylene (BOPP), poly(lactic acid), polyurethanes), fabrics (including cloths) and textiles (such as cotton, wool, polyesters, rayon), clothing, glasses and other minerals, ceramics, silicon surfaces, wood, paper, cardboard, paperboard, cellulose-based materials, glassine, labels, silicon and other semiconductors, laminates, corrugated materials, concrete, bricks, and other building materials. Substrates can in the form of films, papers, wafers, and/or larger three-dimensional objects. 
         [0028]    Substrate  200  can comprise materials that are treated with coatings (such as paints) or similar materials before the layer  210  is applied. Coatings can include indium tin oxide, antimony tin oxide, and similar compositions. 
         [0029]    One or more surfaces of layers  210  and/or  300  can be coated with a reflective material. The reflective material may comprise a metal. Applicable metals include, but are not limited to, silver, aluminum, lead, gold, platinum, rhodium, copper, magnesium, brass, bronze, titanium, zirconium, nickel, tantalum, tin, nickel, tin, steel, and/or colloidal metals. The reflective material can be applied to at least a portion of the one or more internally-facing (i.e. towards the photo-emitter) surfaces utilizing any of the aforementioned deposition methods. Alternatively, the reflective material is applied to at least a portion of the internally-facing surface of the diaphragm in a manner sufficient to reflect light to the photo-collector. The reflective material can be deposited using and applicable deposition method, which includes, but is not limited to, spattering, spraying, plating, syringe deposition, spray coating, electrospray deposition, ink-jet printing, spin coating, thermal transfer (including laser transfer) methods, screen printing, rotary screen printing, gravure printing, capillary printing, offset printing, electrohydrodynamic (EHD) printing, flexographic printing, pad printing, stamping, xerography, microcontact printing, dip pen nanolithography, laser printing, via pen or similar means. 
         [0030]    In certain embodiments, substrate  200  is a water soluble substrate, such as a water soluble polymer. Applicable water soluble polymers include, but are not limited to, alkaline hydrosoluble copolymers of isobutylene and maleic anhydride, ISOBAM™ (developed by Kuraray Co, LTD), BIOCARE™ polymers (developed by DOW Chemicals), CELLOSIZE™ hydroxyethylcellulose (HEC) (developed by DOW Chemical), DOW™ latex powders (DLP) (developed by DOW Chemical), ETHOCEL™ ethylcellulose polymers (developed by DOW Chemical), KYTAMER™ PC polymers (developed by DOW Chemical), METHOCEL™ water soluble resins (developed by DOW Chemical), POLYOX™ water soluble resins, SoftCAT™ polymers (developed by DOW Chemical), UCARE™ polymers (developed by DOW Chemical), Sokalan® (developed by BASF), Tamol® (developed by BASF), polyacrylamides, polyacrylates, acrylamide-dimethylaminoethyl acrylate copolymers, polyamines, polyethyleneimines, polyamidoamines, polyethylene oxide, rice paper, water soluble paper, ASW-60 (developed by Aquasol Corp.), ASW-35 (developed by Aquasol Corp.), ASW-15 (developed by Aquasol Corp.), ASW-40 (developed by Aquasol Corp.), Dissolov Tech PS (developed by DayMark Technologies), and DissolovTeck 35C (developed by DayMark Technologies), and Ambergum™ water-soluble polymers. 
         [0031]    Substrate  200  can be coated with UV-curable water soluble products. Applicable UV-curable water soluble products includes, but is not limited to, Chromafil™ (developed by Chromaline®), CCI Red-Coat (developed by Chemical Consultants, Inc.), isopropanol, Blue Screen Filler No. 60 (developed by Ulano Corp.), Green Extra Heavy Blockout No. 10 (developed by Ulano Corp.), Red Coat Blockout (developed by Lawson Screen Products, Inc.), and Ryo Screen Blockout (developed by Ryonet Corp.).