Abstract:
This application discloses a method for developing a conductive nano-gap. The first step can comprise depositing a brittle material on a substrate. Next, a conductive graphene layer can be deposited at the surface of the brittle material. Lastly, a crack can be propagated through the brittle material and the graphene using a force, the crack a nano-gap.

Description:
BACKGROUND 
       [0001]    This disclosure relates to a method for producing a nano-gap in a brittle film assisted by a stabilizing substrate. 
         [0002]    DNA sequencing is a process used to determine the precise order of four nucleotide bases, which comprise a DNA strand. The information obtained from DNA sequencing is useful to various fields of biology and other sciences, forensics, medicines, agriculture, and other areas of study. One of the challenges of biotechnology is establishing the base sequence of individual molecules of DNA/RNA without PCR amplification or other modifications to the molecule, which can cause reading defects, and contaminations of samples. One known method of DNA sequencing is the conventional Sanger method. This method uses shotgun sequencing that only give portions of the DNA strand and can require many sequencing steps, overlapping reads, and good amount of computational power to merge the sequences. This method can be time consuming and resource intensive, thus can be costly. An alternative method for conventional Sanger method is nano-gap based (nano-pore based) sequencing. In this method, DNA can be passed through a nano-gap. DNA or RNA molecule can be electrophoretically driven in a strict linear sequence through the nano-gap whose width can approximately be a minimum of 1.5 nanometers. The molecule can be detected when the DNA molecules release an ionic current while moving through the nano-gap. Further, the amount of current is very sensitive to the size and shape of the nano-gap. If single nucleotides (bases), strands of DNA or other molecules pass through or is near the nano-gap, a characteristic change in the magnitude of the current is created through the nano-gap. Analyzing the transverse conductance (current) with respect to time the molecules composition can be extrapolated and sequenced. Using nano-gap-based sequencing a large read length and high throughput can be achieved simultaneously. However making nano-electrodes that are aligned with the nano-gap is difficult. 
         [0003]    As such it would be useful to have a method for producing a nano-gap in a brittle film assisted by stabilizing substrate. 
       SUMMARY 
       [0004]    This application discloses a method for developing a conductive nano-gap. The first step can comprise depositing a brittle material on a substrate. Next, a conductive graphene layer can be deposited at the surface of the brittle material. Lastly, a crack can be propagated through the brittle material and the graphene using a force, the crack a nano-gap. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]      FIG. 1  illustrates a side view of a strip comprising a substrate coated with a brittle film. 
           [0006]      FIG. 2  illustrates a conductive two-dimensional (2D) layer deposited at the surface of a strip. 
           [0007]      FIG. 3  illustrates a strip mounted on a microscope. 
           [0008]      FIG. 4  illustrates a top view of a strip marked with one or more indentions. 
           [0009]      FIG. 5  illustrates propagating a crack on a strip. 
           [0010]      FIG. 6  illustrates exemplary measurements that can be used to calculate bending of a substrate. 
           [0011]      FIG. 7  illustrates an exemplary calculation of bending of a substrate. 
           [0012]      FIG. 8  illustrates a nanotechnology system for reading of DNA sequences through a nano-gap. 
       
    
    
     DETAILED DESCRIPTION 
       [0013]    Described herein is a system and method for producing a nano-gap in a brittle film assisted by a stabilizing substrate. The following description is presented to enable any person skilled in the art to make and use the invention as claimed and is provided in the context of the particular examples discussed below, variations of which will be readily apparent to those skilled in the art. In the interest of clarity, not all features of an actual implementation are described in this specification. It will be appreciated that in the development of any such actual implementation (as in any development project), design decisions must be made to achieve the designers&#39; specific goals (e.g., compliance with system- and business-related constraints), and that these goals will vary from one implementation to another. It will also be appreciated that such development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the field of the appropriate art having the benefit of this disclosure. Accordingly, the claims appended hereto are not intended to be limited by the disclosed embodiments, but are to be accorded their widest scope consistent with the principles and features disclosed herein. 
         [0014]      FIG. 1  illustrates a side view of a strip  100  comprising a substrate  101  coated with a brittle film  102 . In one embodiment, substrate  101  can be a Poly-ethylene Terephthalate (PET) film that is used as a stabilizer for strip  100 . Brittle film  102  can comprise of a brittle material  103 , which can include but are not limited to salt, ceramic, or silica glass substance. An example of brittle film  102  is a Spin on Glass (SOG) liquid glass. For purposes of this disclosure, SOG is a type of glass that can be applied as a liquid and cured to form a layer of glass having characteristics similar to those of SiO2. SOG is mainly used for planarization and is a dielectric. 
         [0015]    Brittle film  102  can be deposited onto the surface of substrate  101  through a coating method such as Mayer rod coating. After substrate  101  is coated with brittle film  102 , the thickness of substrate  101  can be measured to ensure that the thickness of strip  100  is within a desired height. The measurement can be taken at a point  104  of strip  100 . Point  104  can be any area within strip  100 . 
         [0016]      FIG. 2  illustrates a conductive two-dimensional (2D) layer  201  deposited at the surface of strip  100 . In a preferred embodiment, conductive 2D layer  201  comprises graphene. For purposes of this disclosure, graphene is a 2 dimensional hexagonal carbon lattice that can survive large transmembrane pressure with intrinsic conductive properties. Therefore, graphene can be ideal for the conductive nano-gap application. After conductive 2D layer  201  is deposited onto the surface of strip  100 , thickness of strip  100  can be measured again at point  104  of strip  100 . Thickness of strip  100  can be measured to determine the resulting thickness after conductive 2D layer  201  is deposited. The quality of conductive 2D layer  201  can also be determined to ensure that a relevant area of conductive 2D layer  201  can still be used as a conductor. Raman spectroscopy can be used to determine the thickness (single layer, bilayer, multilayer), and quality or presence of defects on conductive 2D layer  201 . 
         [0017]      FIG. 3  illustrates strip  100  mounted onto a microscope  300 . In a preferred embodiment, microscope  300  can be an atomic force microscope (AFM). In this embodiment, strip  100  can be placed within the vacuum chamber of microscope  300 . Then, through an AFM scratching technique, one or more indentions  301  can be formed to mark the desired position where a crack should be formed. Such scratching can create a weak point where a crack is most likely to first form. Moreover, indentions  301  can aid microscope  300  to detect where the crack is on strip  100 . Further in another embodiment, microscope  300  can be a scanning electron microscope (SEM). 
         [0018]      FIG. 4  illustrates a top view of strip  100  marked with indentions  301 . To produce an initial gap  401  on conductive 2D layer  201 , a strain can be exerted on indentions  301 . The strain in indentions  301  can produce a crack in brittle film  102  which can produce initial gap  401 . 
         [0019]      FIG. 5  illustrates propagating a crack  501  on strip  100 . After placing indentions  301  on strip  100 , force  500  can be applied to indentions  301  to cause crack  501  in brittle film  102  and conductive 2D layer  201  to propagate. In one embodiment, force  500  can be a compression force, which exerts pressure by squeezing indentions  301 . In another embodiment, force  500  can be a tensional force. In some embodiments, force  500  can be applied by bending strip  100  around a bar or a bending device. In a preferred embodiment, crack  501  can be a break created on brittle film  102  that is within indentions  301 . Since brittle film  102  can have a definite feature at a nano level, when strip  100  is cracked in between indentions  301  through a controlled and supported experiment, a nano-gap  502  can be created on conductive 2D layer  201 . Nano-gap  502  can be a gap within conductive 2D layer  201  that is less than 100 nanometers wide. 
         [0020]      FIG. 6  illustrates exemplary measurements that can be used to calculate bending of substrate  101 . After the processes of propagating crack  501 , nano-gap  502  can widen to as much as 400 nm. As such, substrate  101  can be bent to decrease the distance between nano-gap  502 . Using known measurements on strip  100 , such as a strip thickness  601 , a crack width  602 , and a preferred nano-gap distance, a calculation can be made to determine at what angle of bend on each side of strip  100  can be done in order to produce the preferred nano-gap distance. In one embodiment, substrate  101  can be bended using a suction method, wherein a suction cup can be placed at the bottom of strip  100 , which can cause substrate  101  to bend concavely and thus a relationship between applied pressure and bend degree can be made and stabilized with further processing such as applying a “tack” similar to what is used in the art of welding by metal physical deposition methods. Strip thickness  601  can be the entire thickness of strip  100 , which can comprise substrate  101 , brittle layer  102 , and conductive 2D layer  201 . Furthermore, strip thickness  601  can comprise a thickness of first-side strip  601   a , a thickness of second-side strip  601   b , a height of first-side strip  603   a , and a height of second-side strip  603   b . Thickness of first-side strip  601   a  can be the measure of thickness on one side of strip  100 , while thickness of second-side strip  601   b  can be the measure of thickness on the other side of strip  100 . Additionally, height of first-side strip  603   a  can be the edge on one side of nano-gap  502 , while height of second-side strip  603   b  can be the edge on the other side of nano-gap  502 . Crack width  602  can be the measure of the total distance between crack  501 . Crack width  602  can further comprise a mid-crack distance  604 , a first base point  605   a , a second base point  605   b , and an intersection point  606 . Mid-crack distance  604  can be half of the total distance between crack  501 . First base point  604   a  can be the lowest point on one side of nano-gap  502 , while second base point  604   b  can be the lowest point on the other side of nano-gap  502 . Intersection point  606  can be the common point at which an inward (or center) bend  607  of a 45-degree angle from vertical lines on base points  604   a  and  604   b  meets. For purposes of this disclosure, it is assumed that movement of vertical lines on first base point  604   a  and second base point  604   b  is negligible to none at bending. The control on bending of 
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         [0000]    is the most important process, parameters provide an accurate way to keep C 1 =C 2 . 
         [0021]      FIG. 7  illustrates an exemplary calculation of bending of substrate  101 . In an example measurements shown in  FIG. 7 , wherein thickness of strip  601   a  and  601   b  can be at 400 nm, crack width  602  can be 200 nm, and a preferred nano-gap distance  701  can be 9 nm, an angle of bend  702  can be calculated. Preferred nano-gap distance  603  can be desired distance between nano-gap  502 . Angle of bend  702  can be the required degree of angle at which either ends of substrate  101  can be bent in order to obtain preferred nano-gap distance  701 . Using the equations 
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         [0000]    wherein f=b 1 =b 2  and l 1 =l 2 =45°, angle of bend  702  can be obtained. Thus, using the given measurements in  FIG. 7 , angle of bend  702  can be at 13.8 degree angle. 
         [0022]    Using the law of cosines one can determine the distance that the edge traveled as well as the resulting angle it produces in triangulation with the edge locations, a1, or b1, and a2, or b2 that may prove useful in certain applications. 
         [0023]    To get the distance that the edge traveled on either of the sides of nano-gap  502 , one can use these equation: J=√{square root over (2(C1) 2 −2(C1) 2  cos(l 1 ))} or J=√{square root over (2(C2) 2 −2(C2) 2  cos(l 2 ))}, wherein J is the distance traveled. 
         [0024]    To get the resulting angle produced in triangulation, these equations can be used: 
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         [0025]      FIG. 8  illustrates a nanotechnology system for reading of DNA sequences through nano-gap  502 . The resistive reader system can comprise nano-gap  502  between graphene  201  that connected to a voltage source  801 . Using nano-gap sequencing, nano-gap  502  can initially be immersed in a conducting fluid and a potential voltage can be applied across nano-gap  502 , due to conductions of ions through nano-gap  502  an electric current  802  can be observed. The amount of current  802  can be sensitive to the size and shape of nano-gap  502 . As such, by being able to manipulate and stabilize substrate  101 , a desired width on nano-gap  502  can be obtained, and readings made on resistive reader system can have high accuracy and resolution. 
         [0026]    Various changes in the details of the illustrated operational methods are possible without departing from the scope of the following claims. Some embodiments may combine the activities described herein as being separate steps. Similarly, one or more of the described steps may be omitted, depending upon the specific operational environment the method is being implemented in. It is to be understood that the above description is intended to be illustrative, and not restrictive. For example, the above-described embodiments may be used in combination with each other. Many other embodiments will be apparent to those of skill in the art upon reviewing the above description. The scope of the invention should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. In the appended claims, the terms “including” and “in which” are used as the plain-English equivalents of the respective terms “comprising” and “wherein.”