Manufacturing of solid state nanopore and solid state micropore arrays

Abstract

A method of making a solid-state nanopore or micropore array, the method comprising the steps of: distributing plurality of nanospheres or plurality of microspheres on a substrate; shrinking the plurality of nanospheres or plurality of microspheres on the substrate; depositing a film on the substrate such that the film fills the space around or between the plurality of nanospheres, or the plurality of microspheres; removing the plurality of nanospheres or the plurality of microspheres to form the nanopore or micropore array; forming the three-dimensional geometry (including shape and size) of the plurality of nanopores or the plurality of micropores in the nanopore or micropore array; and processing the substrate material for forming expected through pores or blind pores.

Description

[0001] Title

[0002] Manufacturing of Solid State Nanopore and Solid State Micropore Arrays

[0003] Field of the Invention

[0004] The invention relates to a method of manufacturing solid-state nanopores. Specifically, this method can fabricate a large quantity of solid state nanopores simultaneously in an array, with control over pore size, geometry, pore channel length, density, quantity, structure, and material. It is also applicable for single nanopores and for manufacturing micropores.

[0005] Background to the Invention

[0006] Nanopore is a tiny hole with 1 ~100 nm diameter / width. Biological nanopores are large molecules extracted from nature with a pore naturally formed in the middle, widely existing in cells for essential processes via open-close dynamic motion, such as ion transportation, metabolic activities and current transduction. Although this mechanism is quite attractive and potentially very useful for a variety of applications, currently the commercialization of biological nanopores is limited and their applications are essentially limited to DNA sequencing. Compared with biological nanopores, solid-state nanopores formed in engineering materials are more robust and durable, more flexible in pore size, shape and properties, have a lower requirement on the preservation and utilization environment, and are more compatible with scalable fabrication techniques. Unfortunately, solid-state nanopores have not been commercialized widely due to a lack of cost-effective, efficient, scalable manufacturing techniques for mass production of solid-state nanopores.

[0007] The traditional ways of creating nanopores in engineering materials include focused ion beam (FIB), electron beam lithography (EBL), laser etching, chemical etching, and so on. These methods have intrinsically low efficiency and require complex facilities, and most still create one nanopore at a time which cannot meet the requirements of low cost and high efficiency presented by industry. Although some research produced several to dozens of solid-state nanopores (such as 4, 9, 36 nanopores) based on the traditional methods, they are simply used for proof-of-concept scenarios. Furthermore, rigid combination of single nanopores is not a sustainable way for commercialization, which is evidenced by the unacceptably high price of some commercial devices accommodating over 140,000 biological nanopores. Considering that the size of a wafer in mass production is usually up to centimeter level, the conventional manufacturing techniques are totally insufficient. Therefore, figuring out a solution capable of forming a large quantity of nanopores at a time across an entire wafer is essential to enable many new possibilities in this area.

[0008] CN 104141108 A describes the manufacture of a nanopore array which requires processing the substrate surface for hydrophilicity and removing the nanospheres in three steps. CN 104505408 A describes a method to manufacture a nanopore array with a nanopore diameter of between 200-500nm. CN 114034662 B refers to a portable detection system design, including a description of a method of fabrication of quasi- nanopores. CN 114249325 A describes the use of 500nm nanospheres to manufacture a nanopore array. CN 115692189 A describes controllable chemical etching to form nano-slits. CN117902619 describes a method of manufacturing a nanopore array with a nanopore diameter of between 100-200nm. Yang et al. (Proceedings of the13th IEEE International Conference on Nanotechnology, “patterned ultrathin metal membranes with hexagonally packed sub-50nm nanopore arrays based on hydrophilicity-templated self-assembly monolayer”, pp. 414-417 (2013)) describes the use of parylene deposition and photolithography to manufacture a nanopore array, where hydroxyl groups are formed to make the exposed wafer area hydrophilic, while the covered parylene area is hydrophobic, so that the wafer surface is patterned.

[0009] It is an object of the present invention to overcome at least one of the above-mentioned problems.

[0010] Summary of the Invention

[0011] Although biological nanopores have been successfully commercialized, solid-state nanopores are capable of enabling more robust, sensitive, and reliable devices required by the industry. Thus, it is considered as the next generation nanopore with superior advantages over a biological nanopore. Although many efforts have been devoted to the fabrication of solid-state nanopores in the recent two decades, most laboratory attempts by now have only achieved single solid-state nanopore or a small number of solid-state nanopores in a particular pattern, which is not compatible or efficient for most industrial applications. The main aspect developed by the Applicant is an innovative hybrid manufacturing method for efficiently and cost-effectively providing large scale fabrication of solid-state nanopores. The method combines nano-template fabrication, film deposition, nanopore array forming, 3-dimentional shaping of nanopores, and substrate processing into an integrated process chain (called FAST by the Applicant), as shown in Figure 1. Experiments have provided chip sizes over 10mmx10mm containing several billion nanopores or over 30mmx30mm containing several million micropores, with nanopore size and film thickness down to several nanometers when maintaining a good uniformity of nanopore array. The nanopore size can even reach smaller, such as 1-2nm or below 1 nm. Simulation proved the controllable regulation of nanopore 3D shape, which accorded quite well with experiments and demonstrated a new possibility for fabricating irregular nanopores (such as conical nanopores rather than conventional cylindrical nanopores) in a large scale. The whole cycle of the process chain is faster and cheaper than current processes, which is much favorable to support industrial production and applications.

[0012] The invention described herein is a validated hybrid manufacturing method for fabricating numerous (quantity can be controlled) solid-state nanopores simultaneously, including nano-template fabrication, film deposition, nanopore array formation, 3D shaping and substrate processing.

[0013] Furthermore, detection of large molecules (such as some virions, proteins, cells) usually require pores larger than 100nm in size, even at micrometer level (micropores). The invented method is also applicable to manufacturing pores ranging from 100nm to hundreds of micrometers in size.

[0014] There is provided, as set out in the appended claims, a method of making a solid-state nanopore or micropore array, the method comprising the steps of:

[0015] (a) distributing plurality of nanospheres or plurality of microspheres on a substrate;

[0016] (b) shrinking the plurality of nanospheres or plurality of microspheres on the substrate;

[0017] (c) depositing a film on the substrate such that the film fills the space around or between the plurality of nanospheres, or the plurality of microspheres;

[0018] (d) removing the plurality of nanospheres or the plurality of microspheres to form the nanopore or micropore array; and

[0019] (e) forming (changing) the three-dimensional geometry of the plurality of nanopores or the plurality of micropores in the nanopore or micropore array.

[0020] In one aspect, there is provided a method of making a solid-state nanopore array, the method comprising the steps of: (a) distributing a plurality of nanospheres on a substrate;

[0021] (b) shrinking the plurality of nanospheres on the substrate;

[0022] (c) depositing a film on the substrate such that the film fills the space around or between the plurality of nanospheres;

[0023] (d) removing the plurality of nanospheres to form the nanopore array; and

[0024] (e) forming the three-dimensional geometry of the plurality of nanopores in the nanopore array.

[0025] In one aspect of the methods described herein, there is the proviso that photolithography is excluded from use in step (a) and / or step (d).

[0026] In one aspect the method for comprises the step of (f) processing the substrate to form one or more through pores or one or more blind pores with expected depth. The substrate lies beneath the nanopore or micropore array film. The step here etches a through pore from the top of the array film through to the substrate beneath the film (on which the array film is adhered to) and out the other side of the substrate. For a through pore, the step can also etch from the back of the substrate (opposite side to the pore array film surface), so that the pore channel is continuous from the back of the substrate through to the array film surface or the pores in the film are exposed open on both sides due to the removal of substrate material to form a through pore. In other words, a blind pore is etched from the top of the array film and into the substrate material beneath the film, but does not out go all the way through to the other side of the substrate.

[0027] In one aspect, the processing step (f) removes a part of the substrate in selected areas by means such as reactive ion etching, sputter etching, vapor phase etching, laser machining, wet chemical etching or electric discharge machining.

[0028] In one aspect, the processing step (f) aims to generate through pores, or increase the depth of blind pores, or expose a certain number of through pores in selected areas.

[0029] In one aspect, the film comprises one or more materials selected from a polymer, a metal, a ceramic, a semiconductor, or a composite material. Preferably, the polymer is selected from polytetrafluoroethylene) (PTFE), polyethylene (PE), polyvinylidene fluoride (PVDF), poly(2,5-thienylene) (PTh), poly(pyridine-2-5-diyl) (PPy), an acrylate, a methacrylate, a styrene, vinylpyrrolidone, maleic anhydride, poly(hydroxyethyl methacrylate), poly(2-hydroxyethyl methacrylate), poly(4-vinyl pyridine), and poly(maleic anhydride-co-dimethylacrylamide-codie(ethylene glycol) divinyl ether).

[0030] In one aspect, the metal is selected from platinum, aluminium, iridium, nickel, palladium, gold, silver, tungsten, and associated alloys and metallic oxides.

[0031] In one aspect, the semiconductor is selected from silicon, germanium, gallium arsenide, and silicon carbide.

[0032] In one aspect, the ceramic is selected from SiO2, Si3N4, TiO2, or AI2O3

[0033] In one aspect, the shrinking step (b) is a chemical etching step selected from reactive ion etching, sputter etching, vapor phase etching, and controllable chemical solution etching.

[0034] In one aspect, the shrinking step (b) is performed under vacuum and for between 10-60 minutes. Preferably, the shrinking step (b) uses an etching gas selected from oxygen, hydrogen fluoride, carbon tetrafluoride, and sulphur hexafluoride.

[0035] In one aspect, the 3D forming step (e) comprises placing the nanopore or micropore array in a suitable high temperature environment of close to but below the melting point of the film (and substrate) material (for example, up to about 1 ,300°C for SiO2film on a Si substrate), for periods of between 1 to 240 minutes. Preferably, the period of time is selected from 1 minute, 5 minutes, 10 minutes, 20 minutes, 30 minutes, 45 minutes, 60 minutes, 90 minutes, 120 minutes, and 150 minutes.

[0036] In one aspect, the three-dimensional geometry is the size and shape of the nanopore or micropore.

[0037] In one aspect, the nanospheres or microspheres are functionalised with at least one or more of the following: cetyltrimethylammonium bromide, sodium dodecyl sulfate, or polyethylene glycol.

[0038] In one aspect, the depositing step (c) is by physical vapour deposition, chemical vapour deposition, atomic layer deposition, and similar processes.

[0039] In one aspect, the plurality of nanospheres or plurality of microspheres are spin-coated during step (a). Preferably, the nanosphere spin-coating step comprises accelerating the nanospheres at 300-500 rpm / s with a rotation speed of 600-3000 rpm, and a dwelling time of 50-300s. In one aspect, the microsphere spin-coating step comprises accelerating the microspheres at 100-300 rpm / s with a rotation speed of 100-300 rpm, and a dwelling time of 10-100s. The spin-coating is performed under ambient temperatures or a temperature of up to 80°C.

[0040] In one aspect, the nanopores range in diameter from 0.5 nm to 990 nm.

[0041] In one aspect, the micropores range in diameter from 1 pm to 990 pm.

[0042] In one aspect, the solid state nanopores in the array are spaced between 1 nm-1mm from each other.

[0043] In one aspect, the solid state micropores in the array are spaced between 1 um-1mm from each other.

[0044] In one aspect, the removing step (d) comprises (i) immersing the solid state nanopore array film or the micropore array film in a solvent and applying an energy source for a period of time to remove the plurality of nanospheres or the plurality of microspheres or (ii) by dry chemical etching. Preferably, the solvent is selected from toluene, benzene, ethanol, methanol, propanol, acetone, tetrachloroethylene, toluene, methyl acetate, and ethyl acetate.

[0045] In one aspect, when the removing step (d) is performed by (i) above, the energy source is ultrasound.

[0046] In one aspect, when the removing step (d) is performed by (ii) above, the removing step (d) is performed under vacuum and the period of time is selected from 15, 30, 45, 60, 75, 90, 105, 120, 150, and 180 minutes.

[0047] In one aspect, the dry chemical etching for the removing step (d) is performed using a plasma comprising a reactive gas selected from sulphur hexafluoride, carbon tetrafluoride, oxygen, chlorine, boron trichloride; and optionally including nitrogen, argon, helium and the like.

[0048] In one aspect, the substrate is selected from Si, SiC>2, SisN4, glass, AI2O3, graphene, MOS2, Cu, stainless steel, aluminum, titanium, PTFE, and a proton exchange membrane. In one aspect, the nanosphere or microsphere is composed of polystyrene, SiO2, Au, Ag, CdSe / ZnS, and the like.

[0049] In one aspect, there is provided a solid state nanopore array produced by the method described above.

[0050] In one aspect, there is provided a solid state micropore array produced by the method described above.

[0051] Definitions

[0052] In the specification, the term “nanosphere” should be understood to mean a particle that has a diameter less than 1000nm; preferably less than about 500nm; more preferably less than about 250nm; and ideally less than about 100nm. In one aspect the nanosphere has a diameter equal to or less than 50nm.

[0053] In the specification, the term “microsphere” should be understood to mean a particle that has a diameter larger than 1 pm and less than 1000pm.

[0054] In the specification, the term “nanopore” should be understood to mean a pore or an interstice (small space, gap, hole, or divot) in a membrane (or film) or a substrate that has an internal diameter less than 1000nm; preferably less than about 500nm; more preferably less than about 250nm; and ideally less than about 100nm. In one aspect the nanopore has a diameter equal to or less than 50nm. The terms “membrane” and “film” in this context can be used interchangeably.

[0055] In the specification, the term “micropore” should be understood to mean a pore or an interstice (small space, gap, hole, or divot) in a membrane or substrate that has an internal diameter of between 1 pm - 1000pm.

[0056] In the specification, the term “blind pore” should be understood to mean a nanopore or a micropore that is accessible from one side, but that the other side is blocked (with no open access). Put another way, only one side of a blind pore is open (the opposite side is closed). In the specification, the term “through pore” should be understood to mean a nanopore or a micropore that is open continuously from one side of the pore to the other side of the pore. In other words, both sides of the pore are open.

[0057] In the specification, the term “nanopore array” or “nanopore array film” should be understood to mean a distribution or arrangement of multiple nanopores (in contrast to a single nanopore). The nanopore array of the claimed invention is differentiated from the pores of nanoporous materials because the pores of the latter are totally random in the distribution of the nanopores, without long-range order, while the opposite is true for the former.

[0058] In the specification, the term “micropore array” or “micropore array film” should be understood to mean a distribution or arrangement of multiple micropores (in contrast to a single micropore). Such a distribution or arrangement of micropores is not totally random, instead it can be controlled to form in an ordered way.

[0059] In the specification, the term “film” should be understood to mean a layer of material that accommodates the nanopore or micropore array. The film is usually deposited on the surface of the substrate with a plurality of nanospheres or a plurality of microspheres are embedded, and the film forms between the spheres. The film is typically a polymer, a metal, a ceramic, a semiconductor, or a composite.

[0060] In the specification, the term “three-dimensional (3D) shaping” and “forming the three- dimensional geometry” of the nanopore or micropore should be understood to mean that the size and geometry of the pore is changed or formed to create a blind pore or a through pore having a particular shape and size that is different from the original geometry and size of the nanopore or micropore following removal of the nanosphere or microsphere, respectively, during the array manufacturing process.

[0061] Brief Description of the Drawings

[0062] The invention will be more clearly understood from the following description of an embodiment thereof, given by way of example only, with reference to the accompanying drawings, in which:

[0063] Figure 1 illustrates a solid-state nanopore array fabrication process with (a) a nano-template fabrication, (b) film deposition, (c) nanopore array formation, (d) 3D shaping of the nanopores, (e) substrate processing. Figure 2 illustrates a compact monolayer of nanospheres distributed by spin coating, (a) an SEM image of a monolayer of nanospheres, with the average diameter of 99.3 nm (SD: ±3 nm) in (b). (c) Monolayer topography of an atomic force microscopy (AFM) image, (d) 3D image of the AFM characterization.

[0064] Figure 3 illustrates topography analysis after oxygen (O2) plasma etching, (ai- a3) SEM images after etching for 60 s, 90 s, and 120 s. (bi-b3) AFM 3D topographies corresponding to ai-a3.

[0065] Figure 4 illustrates SEM images of large-scale solid-state nanopore array films with different densities and film thickness. All films were made with a size over 10 mm x10 mm. (a) Compact nanopore array, (b) Looser nanopore array with a selected area amplified, (c) Very loose nanopore array with a selected pore amplified in (d).

[0066] Figure 5 illustrates a novel nanopore shaping phenomenon proved by both experiments and simulation, (a - e) Variation of single solid-state nanopore observed via SEM detection by thermal processing for 0 mins, 10 mins, 20mins, 30 mins and 2.5 hours respectively.

[0067] Figure 6 illustrates SEM images of monolayer nanosphere distribution with different densities. All distributions were made on a sample size over 10 mm x10 mm. a. Compact nanosphere distribution, b. Looser nanosphere distribution, c. Sparse nanosphere distribution with only one nanosphere in the field of view.

[0068] Figure 7 illustrates SEM images of nanosphere over-etching where nanospheres cannot maintain an excellent uniformity in shape and size. Keeping nanopores uniform is an important principle and skill in the process design and control of this patent.

[0069] Detailed Description of the Drawings

[0070] The present invention provides a method of making a solid-state nanopore array or single solid-state nanopore in selected areas. The method is performed by multiple steps as a hybrid method. The current implementation is usually completed by three, four or five steps (referring to Figure 1) depending on the design of the nanopore array. However, the method can be combined with some subsequent steps, or some adjustments can be made to each step. For instance, chemical etching can be used in step (e) to form blind nanopores or micropores in the substrate using the nanopore array or micropore array as the mask, respectively. Figure 1(e) illustrates two more examples with multiple through pores formed (left) and a single through pore formed (right). Chemical etching is a typical technique for silicon-based substrate processing, although some other techniques of precise material removal are also applicable depending on the substrate type, such as laser ablation and electric discharge machining.

[0071] Materials and Methods

[0072] Fabrication for nano-template

[0073] Nanospheres made from different materials (such as polystyrene (PS), Au, Ag, and SiO2) and in different sizes can be used to fabricate the nano-template. The nanospheres can be functionalized (such as with cetyltrimethylammonium bromide (CTAB), sodium dodecyl sulfate (SDS), or polyethylene glycol (PEG)) in order to guarantee the polydispersity, although this is not essential.

[0074] Numerous materials can be used as the substrate, including metals, ceramics, polymers, semiconductors, composites, and so on. Some examples that are commonly used include but not limited to Si, SiO2, Si3N4, glass, AI2O3, graphene, MoS2, Cu, stainless steel, aluminum, titanium, polytetrafluoroethylene (PTFE), and a proton exchange membrane.

[0075] Before dispersing the nanospheres onto the substrate, the substrate is cleaned, as suggested below. Processing of substrate surface for hydrophilicity or hydrophobicity is not mandatory in this invention.

[0076] Dispersing the nanospheres onto the substrate in a controllable way to form the nanotemplate can be achieved by, for example, spin-coating, drop coating, dip coating, electrophoretic deposition, self-assembly at the gas / liquid interface, transfer from the gas / liquid to the gas / solid interface, and the like.

[0077] One example of a process of fabricating the nano-template is provided: PS nanospheres and a commercial silicon wafer (substrate) are used, while spin-coating is utilized to distribute the nanospheres. Before spin-coating the PS nanospheres, the silicon wafer is cleaned by ultrasound in acetone, ethanol and distilled water, respectively, for 10-30 minutes each, and then exposed to O2plasma for 10-30 minutes. The substrate is then dried by nitrogen gas. The examples show that the use of this process can form a monolayer distribution of nanospheres over a large area (see Figure 2). The self-assembly of the PS nanospheres through, for example, spin-coating is affected by multiple factors such as acceleration rate, rotation speed, dwelling time, and temperature. The range of values for these parameters adopted by the inventors is as follows: an acceleration rate of from 300 rpm / s to 600 rpm / s, a rotation speed of from 600 rpm to 3000 rpm, a dwelling time of from 50 s to 300 s, and a temperature from about 20°C to about 80°C. The results are shown in Figure 2, which proves a quite regular monolayer distribution of nanospheres in a compact manner across the whole substrate without any sphere aggregations or multilayer structures. All the experiments shown in Figure 2 were carried out at ambient temperature, atmospheric pressure, and a constant humidity environment in order to minimize any environment uncertainties. All experiments were repeated at least three times. The morphology of the monolayer of nanospheres on the substrate are clearly shown in Figures 2a, 2c and 2d, which shows SEM (scanning electron microscope) and AFM (atomic force microscope) images of a monolayer of nanospheres as per the claimed invention.

[0078] Figure 6a-c show SEM images of the monolayer distribution of 100nm nanospheres at wafer size, illustrating how the density of nanosphere distribution can be controlled using the claimed method.

[0079] Nanosphere sizing

[0080] Controlling the size of the nanospheres is an essential step to set out the space for the subsequent step of film deposition if the nanospheres are in a compact distribution. On the one hand, the use of an optimized nanosphere size leads to the precise control of the dimension of the nanopore; and on the other hand, an increasing interval between each nanosphere means that the material deposition is easier to perform, thus ensuring excellent nanopore structural integrity. One way to directly control the nanopore size without shrinking the nanospheres is to form loose distribution of nanospheres with a gap formed between each other to provide space for subsequent material deposition to form a film (see Figure 6b and Figure 6c). The known nanosphere size directly determines the nanopore size in a predictable way when nanospheres are removed to form the nanopores.

[0081] Another method to control nanopore size of a nanopore array is to use, for example, oxygen plasma etching, which can be used to shrink the PS nanospheres to the expected size in a controllable way. The prepared PS nanosphere monolayer structure was exposed to an isotropic oxygen plasma to reduce the size of the nanospheres. As illustrated in Figure 3, 98.8 nm PS nanospheres were etched down to a 68.9 nm diameter in 120 s. The etching process is controlled by, for example, the duration of the etching step (120 s as per Figure 3) and the etching power (50 W was used as per Figure 3). As can be seen from Figure 3ai-a3, increasing etching time decreases the diameter of the nanospheres. The distance between the nanospheres expands correspondingly. The average diameter from non-etching to etching for 60 s, 90 s and 120 s were individually calibrated (Figure 3), and corresponded to 98.8 ± 1.3 nm, 81.0 ± 2.0 nm, 74.6 ± 2.1 nm and 68.9 ± 1.4 nm respectively. The correlated tolerances are ± 1.3%, ± 2.5%, ± 2.8%, ± 2.0% respectively, which stayed within the same range, thus proving that the method provides and maintains excellent uniformity after etching. The 3D area (1.5 pm x 1.5 pm) of monolayer topographies were obtained by AFM (see

[0082] Figure 3bi-b3), which also demonstrates that the monolayer structures were kept well and the gap increased between the nanospheres.

[0083] The examples provided above used PS nanospheres. For nanosphere materials other than PS, other reagents can be chosen to shrink the nanospheres if they can chemically react with each other, such as SiC>2 nanospheres can be etched by fluorinecontained plasma gas. While plasma etching was used in this example, other means for shrinking nanospheres would also work here, such as a high energy beam or wet chemical etching.

[0084] Film deposition

[0085] Physical vapor deposition (PVD) was used to deposit selected materials onto the nanotemplate. As space exists between the nanospheres on the substrate, the material can penetrate into the space and from a layer of film on the substrate. The deposition temperature is controlled within a suitable range so as not to melt the nanospheres. The film can have one layer of specified materials (such as Pt, Ir, SiO2, Si3N4, or AI2O3) or a multi-layer with different materials in each layer. Generally, the total deposited film thickness should be smaller than the radius of the nanosphere to allow a part of the nanospheres exposed for etching in the next step. However, this will not impede making deep nanopores (or micropores), as the formed thin nanopore film can be used as the mask for chemical etching of the substrate to form deeper holes in the substrate. In this scenario, the nanopores consist of two parts - a deposited film layer and an etched substrate layer, which can be formed of the same material or from different materials. Nanopore array formation

[0086] By removing the nanospheres, nanopores are exposed. As there is no material deposited where the nanospheres were positioned on the substrate, holes are formed when the nanospheres are removed, forming the nanopores. There are multiple methods to remove the nanospheres depending on the nanosphere material and process requirements. For example, a substrate with PS nanospheres can be immersed into a toluene bath and ultrasound can be applied, or oxygen plasma etching can also be used, to remove the PS nanospheres.

[0087] The method of the claimed invention can fabricate a nanopores array (with nanopores having a diameter < 100nm) using 20-100nm nanospheres placed directly on a substrate. The compact distribution of single nanopores (around 69 nm in diameter) with a perfect boundary and excellent uniformity can be seen via the SEM image in Figure 4a. The wafer size is over 10mm x 10mm, containing several billion such nanopores. A looser distribution is illustrated in Figure 4b, and a more dispersed distribution is shown in Figure 4c with a selected nanopore amplified in Figure 4d.

[0088] Forming the 3D geometry of the Nanopore (and Micropore)

[0089] The size and geometry of the nanopore channel can be varied by applying energy to the nanopores using means such as thermal heating, electron / ion beam irradiation, or by depositing materials into the nanopore itself (such as via atomic layer deposition). Figures 5a-d illustrate a variation of the nanopore geometry, created by heating the SiO2nanopore at 1200°C for 0 mins, 10 mins, 20 mins, and 30 minutes, respectively. It can be seen from the images that the top part of the nanopore (near the nanopore film surface) expands while the bottom part of the nanopore (near the substrate surface) shrinks. Closure of nanopores was observed when heating the SiO2nanopore for 2.5 hours at 1200°C (see Figure 5e, where only a very shallow dent is evident on the surface). For the SiO2nanopore array, temperatures between 1100°C and 1300°C will all work for changing the geometry and size of the pores. For the other materials, this method can also be applied but the workable temperature range may be different. Using this method, the size of the nanopores changes and the 3D geometry of nanopore channels also changes (such as from cylindrical to conical). The effective working zone of the nanopore channel can be made thinner and smaller by this heating method. For instance, for conical nanopores, the narrowest part of the nanopore (that with the smallest diameter and thickness along its length) is the effective working zone for molecule detection (based on current signal).

[0090] The above process is not only applicable for nanopore array fabrication, but also applicable for micropore array fabrication. The major difference is in Step (a) of Figure 1 , where microspheres are used instead of nanospheres to fabricate the “microtemplate”, so the pores are formed in micrometer size. The rest of the process remains the same.

[0091] Furthermore, depending on the nanopore / micropore chip design, Step (d) and (e) of Figure 1 is optional, not mandatory. For example, if shallow, blind cylindrical nano- or micro-pores are desired, the process terminates at Step (c). If deep cylindrical nano- or micro-pores are required, Step (c) should be followed by Step (e), while skipping Step (d).

[0092] By measuring the time used in each step, the whole cycle of the claimed process can be currently achieved within 1-3 hours, depending on the nanopore / micropore size and quantity, pore channel length and shape, and nanopore / micropore chip design. The current manufacturing cost is less than 100 EUR for a 30mmx30mm chip, which can be divided into multiple separate chips for independent use. Such a cost-effectiveness and high efficiency is much favorable for supporting high-volume production and industrial applications.

[0093] The evolution of freestanding solid-state nanopores is classically explained by surface tension, with a critical radius R* dictating expansion (R>R*) or shrinkage (R<R*), without pore geometry variation (e.g. cylindrical pore keeps cylindrical in shape). This framework, validated across materials from SiO2to graphene, assumes thermodynamic equilibrium dominated by surface energy minimization. The inventors observed a distinct phenomenon in substrate-supported ultra-thin SiO2film: pores shrink universally, even when R>R*. The phenomenon is applicable to materials used for substrate-supported films. This contradicts the classic model for freestanding systems. The key distinction lies in the substrate’s role: interfacial confinement restricts material migration, inducing asymmetric top expansion and bottom shrinkage, forming conical nanopore geometry. Not being bound by theory, the inventors thus propose substrate confinement as an independent control parameter. Based on the restriction of substrates, the 3D shaping of massive nanopore channels to form conical nanopore geometry, even close the nanopores, is created by an efficient thermal processing method. The method described herein allows for controllable nanopore (and micropore) variation restricted by substrates. The method of the claimed invention produces superior nanopores with high uniformity.

[0094] In the specification the terms "comprise, comprises, comprised and comprising" or any variation thereof and the terms “include, includes, included and including" or any variation thereof are considered to be totally interchangeable and they should all be afforded the widest possible interpretation and vice versa.

[0095] The invention is not limited to the embodiments hereinbefore described but may be varied in both construction and detail.

Claims

Claims1. A method of making a solid-state nanopore or micropore array, the method comprising the steps of:(a) distributing a plurality of nanospheres or a plurality of microspheres on a substrate;(b) shrinking the plurality of nanospheres or plurality of microspheres on the substrate;(c) depositing a film on the substrate such that the film fills the space around or between the plurality of nanospheres, or the plurality of microspheres;(d) removing the plurality of nanospheres or the plurality of microspheres to form the nanopore or micropore array; and(e) forming the three-dimensional geometry of the plurality of nanopores or the plurality of micropores in the nanopore or micropore array.

2. A method of making a solid-state nanopore array, the method comprising the steps of:(a) distributing a plurality of nanospheres on a substrate;(b) shrinking the plurality of nanospheres on the substrate;(c) depositing a film on the substrate such that the film fills the space around or between the plurality of nanospheres;(d) removing the plurality of nanospheres to form the nanopore array; and(e) forming the three-dimensional geometry of the plurality of nanopores in the nanopore array.

3. The method of Claim 1 or Claim 2, with the proviso that photolithography is excluded from use in step (a) and / or step (d).

4. The method of any one of Claims 1 to 3, further comprising the step of (f) processing the substrate to form one or more of a through pore or a blind pore with a defined depth, or a combination thereof.

5. The method of Claim 4, wherein processing step (f) removes part of the substrate by reactive ion etching, sputter etching, vapor phase etching, laser machining, wet chemical etching or electric discharge machining to form the one or more through pore or blind pore with a defined depth.

6. The method of any one of Claims wherein the film comprises one or more materials selected from a polymer, a metal, a ceramic, a semiconductor, or a composite material.

7. The method of Claim 6, wherein the polymer is selected from polytetrafluoroethylene) (PTFE), polyethylene (PE), polyvinylidene fluoride (PVDF), poly(2,5-thienylene) (PTh), poly(pyridine-2-5-diyl) (PPy), an acrylate, a methacrylate, a styrene, vinylpyrrolidone, maleic anhydride, poly(hydroxyethyl methacrylate), poly(2- hydroxyethyl methacrylate), poly(4-vinyl pyridine), and poly(maleic anhydride-co- dimethylacrylamide-codie(ethylene glycol) divinyl ether).

8. The method of Claim 6 or Claim 7, wherein the metal is selected from platinum, aluminium, iridium, nickel, palladium, gold, silver, tungsten, and associated alloys and metallic oxides.

9. The method of any one of Claims 6 to 8, wherein the semiconductor is selected from silicon, germanium, gallium arsenide, and silicon carbide.

10. The method of any one of Claims 6 to 9, wherein the ceramic is selected from SiO2, SislSk, TiO2, or AI2O311 . The method of any one of the preceding claims, wherein the shrinking step (b) is a chemical etching step selected from reactive ion etching, sputter etching, vapor phase etching, and controllable chemical solution etching.

12. The method of Claim 11 , wherein the shrinking step (b) uses an etching gas selected from oxygen, hydrogen fluoride, carbon tetrafluoride, and sulphur hexafluoride.

13. The method of any one of the preceding claims, wherein the shrinking step (b) is performed under vacuum and for between 10-60 minutes.

14. The method of any one of the preceding claims, wherein the 3D forming step (e) comprises placing the nanopore or micropore array in a high temperature environment of close to, but below the melting point of the film material for periods of between 1 to 240 minutes.

15. The method of any one of the preceding claims, wherein the nanospheres or microspheres are functionalised with at least one or more of the following: cetyltrimethylammonium bromide, sodium dodecyl sulfate, or polyethylene glycol.

16. The method of any one of the preceding claims, wherein the depositing step (c) is by physical vapour deposition, chemical vapour deposition, atomic layer deposition, and similar processes.

17. The method of any one of the preceding claims, wherein the plurality of nanospheres or plurality of microspheres are spin-coated during step (a).

18. The method of Claim 17, wherein the nanosphere spin-coating step comprises accelerating the nanospheres at 300-500 rpm / s with a rotation speed of 600-3000 rpm, and a dwelling time of 50-300s, under ambient temperature or a temperature up to 80°C, or wherein the microsphere spin-coating step comprises accelerating the microspheres at 100-300 rpm / s with a rotation speed of 100-300 rpm, and a dwelling time of 10-100s under a temperature between ambient temperature and 80°C.

19. The method of any one of the preceding claims, wherein the nanopores range in diameter from 0.5 nm to 990 nm and wherein the micropores range in diameter from 1 pm to 990 pm.

20. The method of any one of the preceding claims, wherein the solid state nanopores in the array are spaced between 1 nm-1 mm from each other or wherein the solid state micropores in the array are spaced between 1 um-1 mm from each other.

21. The method of any one of the preceding claims, wherein the removing step (d) comprises (i) immersing the solid state nanopore array film or the micropore array film in a solvent and applying an energy source for a period of time to remove the plurality of nanospheres or the plurality of microspheres or (ii) by dry chemical etching.

22. The method of Claim 21 , wherein when the removing step (d) is performed by (i), the energy source is ultrasound.

23. The method of any one of Claims 21 or 22, wherein when the removing step (d) is performed by (ii), the removing step (d) is performed under vacuum and the period of time is selected from 15, 30, 45, 60, 75, 90, 105, 120, 150, and 180 minutes.

24. The method of Claim 21 , wherein the dry chemical etching is performed using a plasma comprising a reactive gas selected from sulphur hexafluoride, carbon tetrafluoride, oxygen, chlorine, boron trichloride; and optionally including nitrogen, argon, helium and the like.

25. The method of any one of the preceding claims, wherein the substrate is selected from Si, SiO2, Si3N4, glass, AI2O3, graphene, MoS2, Cu, stainless steel, aluminum, titanium, PTFE, and a proton exchange membrane.

26. The method of any one of the preceding claims, wherein the nanosphere or microsphere is composed of polystyrene, SiO2, Au, Ag, and CdSe / ZnS.

27. A method of making a solid-state nanopore array, the method comprising the steps of:(a) distributing a plurality of nanospheres on a substrate;(b) shrinking the plurality of nanospheres on the substrate;(c) depositing a film on the substrate such that the film fills the space around or between the plurality of nanospheres;(d) removing the plurality of nanospheres to form the nanopore array, with the proviso that photolithography is excluded from use in step (d); and(e) forming the three-dimensional geometry of the plurality of nanopores in the nanopore array by placing the nanopore array in a high temperature environment of close to, but below, the melting point of the film material for periods of between 1 to 240 minutes.

28. A solid state nanopore array produced by the method of Claim 1 , Claim 2, or Claim 27.

29. A solid state micropore array produced by the method of Claim 1 .

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