Patent Application
20170327935
The present invention relates generally to methods and compositions for fabrication of patterned surfaces and nanostructures by hot-pulling of metallic glass.
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Without limiting the scope of the invention, its background is described in connection with hot-pulling of metallic glass to form patterned surfaces and nanostructures.
U.S. Pat. No. 8,236,368, entitled, “Method for preparing a hollow microneedle” discloses a method for preparing a hollow microneedle by preparing a solid microneedle by drawing lithography; plating the surface with a metal; removing the solid microneedle; and fabricating the hollow microneedle. The present invention ensures efficient preparation of a hollow microneedle with desired hardness, length, and diameter, and which may be effectively used for extracting internal analytical materials from the body and for drug injection.
U.S. Pat. No. 7,627,938, entitled, “Tapered hollow metallic microneedle array assembly and method of making and using the same,” describes devices, systems, method of using and making a microneedle array including the steps of forming one or more pins on a substrate, depositing one or more layers on the one or more pins and the substrate, exposing a portion of the one or more pins, and separating the one or more pins from the one or more layers to form the hollow microneedle array.
U.S. Pat. No. 7,597,814, entitled, “Structure formed with template having nano-scale features,” describes a method of fabricating ordered patterns of nano-scale objects on a substrate surface.
U.S. Patent Application Publication No. 2009/0045720, entitled, “Method for producing nanowires using porous glass template, and multi-probe, field emission tip and devices employing the nanowires,” describes a method for producing nanowires, which features the use of a porous glass template in combination with a solid-liquid-solid or vapor-liquid-solid process for growing nanowires which are highly straight and have nanoparticles precisely arranged therein.
PCT Patent Application Publication No. WO2008/096335, entitled, “Producing an array of nano-scale structures on a substrate surface via a self-assembled template,” describes a method for producing an array of nano-scale structures on a substrate surface, via a self-assembled template.
The present invention provides a method for creating hundreds to thousands of metallic glass nano-features simultaneously for any aspect-ratio using inexpensive micro-templates to provide high surface area in integrated circuit design. The present invention provides a method for the fabrication of very-high-aspect-ratio structures from metallic glasses. The present invention provides a method for nondestructive demolding of templates after thermoplastic molding of metallic glass features. Prior to the present invention it has been challenging because of high molding pressure required to fill long cavities in templates; the templates used for molding of nano-scale metallic glasses are expensive and disposable; and the fabrication of patterned surfaces and free nanostructures require two different processing steps.
The present invention provides a method of preparing metallic glass nano-structures comprising the steps of: providing a metallic glass composition on a first surface; heating the metallic glass composition to a temperature; contacting a template surface to the metallic glass composition; applying a strain by moving the template surface away from the metallic glass composition to form nano-structures on the template surface and on the first surface; and annealing the nano-structures to form crystallized metallic glass nano-structures. The method may include the step of adjusting the strain and the temperature, or both. The nano-structures may include metallic glass nano-tips, metallic glass nano-rods, metallic glass nano-tubes, metallic glass nano-needles, metallic glass nano-wires, metallic glass nano-features, metallic glass micro-features or combinations thereof. The aspect-ratio of the nano-structures may include greater than 800 or 1000, e.g., 800, 825, 850, 875, 900, 925, 950, 975, 1000, 1025, 1050, 1075, 1100, 1125, 1150, 1175, 1200, 1225, 1250, 1275, 1300, 1325, 1350, 1375, 1400, 1425, 1450, 1475, 1500, 1550, 1600, 1650, 1700, 1800, 1900, 2000, 2100, 2200, 2300, 2400, 2500, 2600, 2700, 2800, 2900, 3000, 3500, 4000, 4500, 5000, 5500, 6000, 6500, 7000, 8000, 9000, 10000 or incremental variations thereof. The template surface or both may include silicon, quartz, metal, and polymer. The metallic glass composition may include Pt, Pd, Ni, Zn or a combination thereof, e.g., Pt57.5Cu14.7Ni5.3P22.5; Pd43Cu27Ni10P20; Ni60Pd20P17B3; Zr35Ti30Cu8.25Be26.75; Zr51Ti9Cu15Be25; Zr54Ti11Cu12.5Be22.5; Zr41.2Ti13.8Ni10Cu12.5Be22.5; Zr46.75Ti8.25Ni10Cu7.5Be27.5; Pd43Ni10Cu27P20; Pt60Ni15P25; Ce68Cu20Al10Nb2; Au49Ag5.5Pd2.3Cu26.9Si16.3; Zr36.6Ti31.4Nb7Cu5.9Be19.1; Ti48Zr20V12Cu5Be15 or a combination thereof.
The present invention provides a method of preparing metallic glass nano-structures comprising the steps of: providing a metallic glass composition on a first surface; heating the metallic glass composition to a temperature to form an amorphous metallic glass composition; contacting a template surface to the amorphous metallic glass composition; applying a strain by moving the template surface away from the amorphous metallic glass composition to form amorphous nano-structures on the template surface and on the first surface; and annealing the amorphous nano-structures to form crystallized metallic glass nano-structures. The method may include the step of adjusting the strain and the temperature, or both. The nano-structures may include metallic glass nano-tips, metallic glass nano-rods, metallic glass nano-tubes, metallic glass nano-needles, metallic glass nano-wires, metallic glass nano-features, metallic glass micro-features or combinations thereof. The aspect-ratio of the nano-structures may include greater than 800 or 1000, e.g., 800, 825, 850, 875, 900, 925, 950, 975, 1000, 1025, 1050, 1075, 1100, 1125, 1150, 1175, 1200, 1225, 1250, 1275, 1300, 1325, 1350, 1375, 1400, 1425, 1450, 1475, 1500, 1550, 1600, 1650, 1700, 1800, 1900, 2000, 2100, 2200, 2300, 2400, 2500, 2600, 2700, 2800, 2900, 3000, 3500, 4000, 4500, 5000, 5500, 6000, 6500, 7000, 8000, 9000, 10000 or incremental variations thereof. The template surface or both may include silicon, quartz, metal, and polymer. The metallic glass composition may include Pt, Pd, Ni, Zn or a combination thereof, e.g., Pt57.5Cu14.7Ni5.3P22.5; Pd43Cu27Ni10P20; Ni60Pd20P17B3; Zr35Ti30Cu8.25Be26.75; Zr51Ti9Cu15Be25; Zr54Ti11Cu12.5Be22.5; Zr41.2Ti13.8Ni10Cu12.5Be22.5; Zr46.75Ti8.25Ni10Cu7.5Be27.5; Pd43Ni10Cu27P20; Pt60Ni15P25; Ce68Cu20Al10Nb2; Au49Ag5.5Pd2.3Cu26.9Si16.3; Zr36.6Ti31.4Nb7Cu5.9Be19.1; Ti48Zr20V12Cu5Be15 or a combination thereof.
The present invention provides method of preparing a metallic glass hollow nano-needle comprising the steps of: providing a metallic glass composition on a first surface; heating the metallic glass composition to a temperature to form an amorphous metallic glass composition; contacting a template surface to the amorphous metallic glass composition; applying a strain by moving the template surface away from the amorphous metallic glass composition to form an amorphous metallic glass hollow nano-needle on the template surface and on the first surface; and annealing the amorphous metallic glass hollow nano-needle to form a crystallized metallic glass hollow nano-needle.
The method may include the step of adjusting the strain and the temperature, or both. The nano-structures may include metallic glass nano-tips, metallic glass nano-rods, metallic glass nano-tubes, metallic glass nano-needles, metallic glass nano-wires, metallic glass nano-features, metallic glass micro-features or combinations thereof. The aspect-ratio of the nano-structures may include greater than 800 or 1000, e.g., 800, 825, 850, 875, 900, 925, 950, 975, 1000, 1025, 1050, 1075, 1100, 1125, 1150, 1175, 1200, 1225, 1250, 1275, 1300, 1325, 1350, 1375, 1400, 1425, 1450, 1475, 1500, 1550, 1600, 1650, 1700, 1800, 1900, 2000, 2100, 2200, 2300, 2400, 2500, 2600, 2700, 2800, 2900, 3000, 3500, 4000, 4500, 5000, 5500, 6000, 6500, 7000, 8000, 9000, 10000 or incremental variations thereof. The template surface or both may include silicon, quartz, metal, and polymer. The metallic glass composition may include Pt, Pd, Ni, Zn or a combination thereof, e.g., Pt57.5Cu14.7Ni5.3P22.5; Pd43Cu27Ni10P20; Ni60Pd20P17B3; Zr35Ti30Cu8.25Be26.75; Zr51Ti9Cu15Be25; Zr54Ti11Cu12.5Be22.5; Zr41.2Ti13.8Ni10Cu12.5Be22.5; Zr46.75Ti8.25Ni10Cu7.5Be27.5; Pd43Ni10Cu27P20; Pt60Ni15P25; Ce68Cu20Al10Nb2; Au49Ag5.5Pd2.3Cu26.9Si16.3; Zr36.6Ti31.4Nb7Cu5.9Be19.1; Ti48Zr20V12Cu5Be15 or a combination thereof.
The present invention provides a crystallized metallic glass nano-structures comprising: a crystallized metallic glass nano-structure extending from a substrate, wherein the crystallized metallic glass nano-structures has an aspect ratio greater than 1000 and comprises Pt57.5Cu14.7Ni5.3P22.5; Pd43Cu27Ni10P20; Ni60Pd20P17B3; Zr35Ti30Cu8.25Be26.75; Zr51Ti9Cu15Be25; Zr54Ti11Cu12.5Be22.5; Zr41.2Ti13.8Ni10Cu12.5Be22.5; Zr46.75Ti8.25Ni10Cu7.5Be27.5; Pd43Ni10Cu27P20; Pt60Ni15P25; Ce68Cu20Al10Nb2; Au49Ag5.5Pd2.3Cu26.9Si16.3; Zr36.6Ti31.4Nb7Cu5.9Be19.1; Ti48Zr20V12Cu5Be15 or a combination thereof.
For a more complete understanding of the features and advantages of the present invention, reference is now made to the detailed description of the invention along with the accompanying figures and in which:
While the making and using of various embodiments of the present invention are discussed in detail below, it should be appreciated that the present invention provides many applicable inventive concepts that can be embodied in a wide variety of specific contexts. The specific embodiments discussed herein are merely illustrative of specific ways to make and use the invention and do not delimit the scope of the invention.
To facilitate the understanding of this invention, a number of terms are defined below. Terms defined herein have meanings as commonly understood by a person of ordinary skill in the areas relevant to the present invention. Terms such as “a”, “an” and “the” are not intended to refer to only a singular entity, but include the general class of which a specific example may be used for illustration. The terminology herein is used to describe specific embodiments of the invention, but their usage does not delimit the invention, except as outlined in the claims.
Steps or procedures, sub-steps or sub-procedures, equipment, reagents, and materials, as well as operation and implementation, of exemplary preferred embodiments, alternative preferred embodiments, specific configurations, and, additional and optional aspects, characteristics, or features, thereof, of the method for producing (fabricating) an array of nanoscale structures on a substrate surface, according to the present invention, are better understood with reference to the following illustrative description and accompanying drawings.
As used herein, the term ‘feature’ and/or ‘features’, as used herein, refers to distinct, distinguishing, or characterizing, parts (e.g., structures, sub-structures, elements, sub-elements) of an object or entity. Accordingly, the term ‘features’, as used herein, refers to, for example, distinct, distinguishing, or characterizing, parts (e.g., structures, sub-structures, elements, sub-elements) of a surface. Herein, exemplary features, i.e., distinct, distinguishing, or characterizing, parts (e.g., structures, sub-structures, elements, sub-elements), of a surface of a self-assembled template, are: facets, grooves, tips, rods, tubes, wires, and steps. Herein, these exemplary features are indicated as being of ‘nanoscale’, i.e., nanofacets, nanogrooves, nano-tips, nano-rods, nano-tubes, nano-wires, and nanosteps, respectively, where the term ‘nano’, other terms prefixed by the term ‘nano’, and phrases including ‘nano’ terms, are each defined immediately following.
As used herein, the term ‘nano’, as used herein, refers to the prefix (symbol ‘n’) of the unit, meter (symbol ‘m’) in the SI (International System of Units) system of units denoting a factor of 10−9, of a size dimension (e.g., length, width, height (thickness), depth, diameter, pitch), expressed in terms of nanometer or nanometers, each abbreviated or symbolized as ‘nm’. The term ‘nano’ is also used herein as a prefix of, and combined with, each of various other terms, for indicating that the ‘other’ term, i.e., feature(s), structure(s), element(s), or characteristic(s), has (have), or is (are) associated with, at least one size dimension (e.g., length, width, height (thickness), depth, diameter, pitch) in the range of between about one (1) nanometer (nm) and about one-thousand (1000) nanometers (nm) [one (1) micron].
As used herein, the term ‘nano’ is used as a prefix of, and combined with, each of the following terms (expressed in singular form, or in plural form, i.e., with the suffix ‘s’ (s)): facet(s), groove(s), grooved, step(s), stepped, wire(s), strip(s), particle(s), belt(s), pattern(s), and scale. Accordingly, the following ‘nano’ terms (expressed in singular form, or in plural form, i.e., with the suffix‘s’ (s)) are used herein: nanofacet(s), nanogroove(s), nanogrooved, nanostep(s), nanostepped, nanotip(s), nanotube(s), nanorod(s), nanowire(s), nanostrip(s), nanoparticle(s), nanobelt(s), nanopattern(s), and nanoscale. Thus, herein, each of the following ‘nano’ terms: nanofacet(s), nanogroove(s), nanostep(s), nanowire(s), nanostrip(s), nanoparticle(s), nanobelt(s), and nanopattern(s), is used for indicating that the feature(s), structure(s), element(s), or characteristic(s)), i.e., facet(s), groove(s), step(s), wire(s), tip(s), rod(s), tube(s), wire(s), strip(s), particle(s), belt(s), or pattern(s), respectively, has (have), or is associated with, at least one size dimension (e.g., length, width, height (thickness), depth, diameter, pitch), whose value or magnitude is in the range of between about one (1) nanometer (nm) and about one-thousand (1000) nanometers (nm) [one (1) micron].
Thus, in a similar manner of usage, the ‘nano’ phrase, nanoscale feature(s), as used herein, refers to a feature (features) (typically, on a surface) which has (have), or is (are) associated with, at least one size dimension (e.g., length, width, height (thickness), depth, diameter, pitch), whose value or magnitude is in the range of between about one (1) nanometer (nm) and about one-thousand (1000) nanometers (nm) [one (1) micron].
Thus, in a similar manner of usage, the ‘nano’ phrase, nanoscale structure(s), as used herein, refers to a structure (structures) (typically, on a surface) which has (have), or is (are) associated with, at least one size dimension (e.g., length, width, height (thickness), depth, diameter, pitch), whose value or magnitude is in the range of between about one (1) nanometer (nm) and about one-thousand (1000) nanometers (nm) [one (1) micron].
As used herein, the phrase ‘substrate surface’, as used herein, refers to a surface of a substrate, where the term ‘substrate’, as used herein, refers to an underlying layer, i.e., of a surface. In general, the substrate, or underlying layer, is composed of essentially any type or kind of material or substance, or combination of materials or substances. More specifically, the substrate, or underlying layer, is composed of inorganic matter, or/and organic matter.
As used herein, the term ‘replicating’, as used herein, refers to copying or reproducing an object or entity. In the context of illustratively describing the method of the present invention, an example of such an object or entity is ‘at least part of an array of nanoscale features’ which is included on a surface of a self-assembled template. Accordingly, the term ‘replicating’, as used herein, refers to copying or reproducing ‘at least part of an array of nanoscale features’ which is included on a surface of a self-assembled template. Thus, in a similar manner of usage, the term ‘replica’, as used herein, refers to a copy or reproduction of an object or entity. In the context of illustratively describing the method of the present invention, an example of such an object or entity is ‘at least part of an array of nanoscale features’ which is included on a surface of a self-assembled template. Accordingly, the term ‘replica’, as used herein, refers to a copy or reproduction of ‘at least part of an array of nanoscale features’ which is included on a surface of a self-assembled template.
As used herein, the term ‘about’, as used herein, refers to ±20% of the associated value. The phrase ‘room temperature’, as used herein, refers to a temperature in a range of between about 15° C. and about 35° C.
Prior to the present invention it has been challenging to make very high-aspect ratio nanowires because of high molding pressure required to fill long cavities in templates. The present inventors overcame the high pressure requirement by template-free elongation of the structures of metallic glass arrays which requires very low pressure. The prior art uses templates for molding of micro- and nano-scale metallic glasses but they are expensive and disposable. The present invention resolved these issues by high-temperature nondestructive demolding that allows reuse of templates. In addition, nano-scale features are created by deformation of large features which are fabricated by using less expensive templates. Another concern with the methods used in the prior art is the fact that the fabrication of patterned surfaces and free nanostructures require two different processing steps. The present invention by its very nature intrinsically creates patterned surfaces and free nanostructures in a single step.
The instant method provides a batch fabrication which can produce thousands of metallic glass nano-wires simultaneously. The existing reusable template only works for low-aspect-ratio features whereas the present invention is suitable for fabrication of features of any aspect-ratio. All existing technologies for fabrication of metallic glass nanostructures require expensive nano-templates. In contrast, the present invention utilizes inexpensive micro-templates and creates nanostructures by subsequent template-free reduction in size. The present invention provides methods of fabrication of nano-wires and nano-tubes from any metallic glasses which have good thermoplastic forming ability.
The present invention provides a method to create nano-scale metallic glass features using micro-scale templates which are inexpensive compared to nano-scale templates. Nano-scale and macro-scale structures are being fabricated using thermoplastic molding of metallic glasses against templates; however, template-based thermoplastic molding suffers major hurdles such as: shallow features due to increase in processing pressure with increasing aspect-ratio and use of expensive disposable templates. The proposed method manipulates the flow behavior of metallic glasses to either enable complete demolding, or deform in a predictable manner. Demolding allows reuse of templates that was not possible in the past. Controlled deformation enables fabrication of nanostructures by mechanical size-reduction of larger metallic glass features. With exact control of temperature, viscosity, strain-rate, strain, anchoring, and initial feature geometry, massive fabrication of metallic glass nanostructures such as: nano-tips, nano-rods, nano-tubes, and nano-wires with controllable aspect-ratios are possible. This approach allows simultaneous fabrication of patterned metallic surfaces and metallic nanostructures aligned on templates.
Currently, no method exists to create nano-scale metallic glass features for any aspect-ratio using micro-scale templates. Most of the current designs directly use nano-scale templates to produce nano-scale metallic features; however, these template-based metallic molding experience major difficulties, which includes but is not limited to low aspect-ratio and high cost of nano-scale templates. The present invention can create nano-scale features with high-aspect-ratios (exceeding 1000) by simple mechanical elongation of micro-scale features.
The present invention provides a new method for simultaneously producing thousands of nano-scale metallic glass features using inexpensive micro-scale templates. It also provides a method for creating nano-scale features for any aspect-ratio by mechanical elongation of micro-scale features. The method used in the creation of these nano-scale metallic features will generate patterned surfaces and free standing metallic glass nanostructures simultaneously that do not require additional assemblage on templates.
Metallic glasses are emerging engineering materials because of their unique mechanical properties and polymer-like thermoplastic processing. Structures ranging from nano- to macro-scale have been fabricated by thermoplastic molding of metallic glasses against templates. However, template-based thermoplastic molding suffers major hurdles such as: shallow features due to increase in processing pressure with increasing aspect-ratio and use of expensive disposable templates. High molding pressure is a consequence of friction between the metallic glass and the templates walls. Template-free elongation of metallic glasses has been suggested as a possible solution to overcome the high pressure requirement for high-aspect-ratio structures. However, low-yield of elongation process prevents the mass production of metallic nanostructures required for applications such as catalysts, sensors, or electrodes. The use of disposable molds is related to demolding issues of metallic glasses from templates. After molding and cooling, the metallic glass structures get mechanically locked in templates and cannot be separated without sacrificing the templates. This issue amplifies for features of higher aspect-ratios due to increased contact area. The present invention overcomes these hurdles of template non-reusability and mass production of metallic glass nanostructures.
The present invention manipulates the flow behavior of metallic glasses to either enable complete demolding or deforming in a predictable manner. Demolding allows reuse of templates that was not possible in the past. Controlled deformation enables fabrication of nanostructures by mechanical size-reduction of larger metallic glass features. Therefore, nano-scale metallic glass features are created using micro-scale templates which are inexpensive compared to nano-scale templates. With exact control of temperature (viscosity), strain-rate, strain, anchoring, and initial feature geometry, the present invention can massively fabricate metallic glass nanostructures such as: nano-tips, nano-rods, nano-tubes, and nano-wires with controllable aspect-ratios. The present invention allows simultaneous fabrication of patterned metallic surfaces and metallic nanostructures aligned on templates.
One embodiment of the present invention provides a method of making metallic glass nanostructures comprising the steps of hot pressing a metallic glass into a micro-template followed by hot pulling the metallic glass composition under controlled conditions. This process is demonstrated in
Another example of the present invention includes nano-tubes that are shaped into hollow nanoneedles for permitting transport of substances there through. The hollow nanoneedles have a length of between about 10 nm and 1000000 nm, inner diameters of between about 2 nm and 100000 nm and a wall thickness of between about 2 nm and 10000 nm. However, other embodiments may have diameters (e.g., 1-100, 400-600, 600-800 and 800-1000 nm) and walls of different thickness (e.g., 1-10, 20-40, 40-60, 60-80, 80-100, 80000-100000 nm). Additionally, the microneedle may include one or more agents located in or on the surface of the microarray, within the layers of the microarray, within said one or more elongated hollow needles of the microarray or combinations thereof.
Metallic glasses inherit many traits of constituent metal elements such as electrical, thermal, and optical properties but yet become malleable at temperatures well below the melting point. The viscous softening of metallic glasses has been utilized in various shaping operations such as embossing, extrusion, joining, rolling, and blow molding. In particular, embossing of metallic glasses is emerging as a novel precision metal fabrication technique due to its ability to mold micro and nanoscale structures by simple hot-pressing against a template. The method has been used in fabrication of textured metal surfaces to understand the effect of topography on wetting, cellular response, reflectance, and catalytic activity. Embossing, however, faces inherently rising flow resistance with increasing aspect-ratio or decreasing size of features. The problem can be best described by analyzing the filling kinetics of a cylindrical cavity (length=L & diameter=d) with a metallic glass during thermoplastic embossing. The required pressure (P) can be estimated by modified Hagen-Poiseuille flow equation:
Where t is the embossing time, η and γ are respectively the viscosity and the surface tension of metallic glass, θ is the contact angle between the metallic glass and the template, h is the thickness of the oxide layer on metallic glass surface, and Co is a constant that depends on the mechanical properties of the oxide film (strength and Poisson's ratio). The first term arises from the template friction and scales as a square of feature aspect-ratio (L/d). The second term is the capillary pressure which renders positive for typical non-wetting conditions (θ>90°) at the template metallic glass interface. The third term is the pressure required to break the rigid oxide skin to allow the flow of metallic glass supercooled liquid. By using the typical embossing parameters (η=107 Pa·s and t=60 s), the first term alone approaches 500 MPa for an aspect-ratio of 10. The opposing capillary pressure and the oxide layer resistance impose additional constraints for embossing of nanoscale features. Besides these intrinsic flow barriers, the applied pressure and the resulting feature aspect-ratio are also limited by the strength of the template. Increasing aspect-ratio is crucial to enhance the performance of metal nanostructures in applications based on surface driven phenomenon such as sensing, electrochemical, light scattering, and catalytic activities. Characterization of nanoscale properties also requires at least one dimension of nanostructures to be large in order to grip and manipulate them.
The fundamental challenges in embossing of high aspect-ratio nanostructures are common to all thermoplastic materials but are exacerbated in metallic glasses due to their higher viscosity, surface tension, and rate of oxidation. Various strategies such as lowering the viscosity by processing at higher temperature or promoting wetting by surface modification, have been tested to reduce the embossing pressure. While the access to lower viscosity is certainly beneficial but the available processing time diminishes due to fast devitrification (glass to crystal transformation) kinetics at higher temperature. In addition, preventing oxidation of metallic liquids at high temperature requires an elaborate embossing set up equipped with vacuum or inert environment. The surface modification approach can only lower the capillary resistance but the dominant first term in equation (1) remains unaffected. Consequently, despite considerable efforts it is still challenging to produce high aspect-ratio nanostructures by thermoplastic embossing of metallic glasses.
The proliferation of metallic glass embossing is further hindered by inability to produce unattached nanostructures. After embossing, the nanostructures remain attached to the metallic glass substrate which hampers their characterization and applications. Separation of nanostructures from their base metallic glass is achieved through laborious focused-ion-beam (FIB) machining which severely limits the yield and the scope of embossed nanostructures. Herein, the inventors present an array drawing technique to enable fabrication of solid and hollow nanostructures (aspect-ratios>1000) from metallic glass formers of any wetting and oxidation characteristics. The resulting nanostructures are detached from the parent metallic glass and can be assembled on various substrates (silicon, quartz, metal, and polymer) or released in free form. Moreover, the nanostructures are synthesized by thermomechanical size reduction of larger features which allows the use of less expensive templates made by photolithography or simple micromachining. The inventors demonstrate that the array drawing technique is very versatile and can be easily tuned to generate assembled: nano-tips, nano-wires, nano-tubes, or nanoscale tensile specimens from diverse metallic glass formers. These nanostructures retain their amorphous structure in the as-prepared state but can be crystallized by subsequent annealing.
Pt-based (Pt57.5Cu17.7Ni5.3P22.5), Pd-based (Pd43Cu27Ni10P20), and Ni-based (Ni60Pd20P17B3) metallic glasses were prepared by using melting, fluxing, and water quenching procedures. Zr-based (Zr35Ti30Cu8.25Be26.75) metallic glass was acquired from LiquidMetal technologies. Aluminum and quartz templates were made by mechanical milling using carbide micro drill bits. Si templates (features with aspect-ratios of 4-5) were prepared by deep-reactive-ion-etching (DRIE). The typical thermoplastic processing temperatures for Pt-based, Pd-based, Ni-based, and Zr-based metallic glasses were 538 K (Tg=503 K), 633 K (Tg=575 K), 653 K (Tg=605 K), and 668 K (Tg=578 K), respectively. All thermoplastic experiments were conducted in air using custom-built heating platens installed on Instron 5966 mechanical tester. The templates and the metallic glass discs were mechanically secured with the lower and the upper heating plates, respectively. The metallic glass discs were first slowly (<0.5 mm/min) pressed on the templates followed by pulling at different speeds (0.5-80 mm/min) till rupture. The filling aspect-ratio of 2-3 was necessary during pressing to prevent subsequent demolding during pulling. Scanning electron microscopy (SEM) imaging was performed using Hitachi S-4300.
Metallic glass supercooled liquids exhibit a variety of flow behaviors (Newtonian, non-Newtonian, and shear-localized) depending on the temperature (viscosity) and the strain-rate (
The sample shapes observed in our extensional studies are consistent with fracture morphologies reported in high-temperature tensile tests of metallic glasses, fiber drawing, and filament stretching of polymer melts. These previous studies have shown that Newtonian fluids neck while viscoelastic fluids can be drawn into threads of uniform diameters before break up during extensional deformation. Our drawings with a single metallic glass structure reveal three important outcomes: (1) the diameter, the aspect-ratio, and the shape of the structure can be tuned without changing the template, (2) two replicas of the structure are formed after rupture, and (3) high strain-rate pulling results in template demolding. These findings serve as guidelines for developing a scalable drawing technique for metallic glass nanostructures.
This is achieved by decoupling the interfacial effects from nanofabrication. The wetting and oxidation properties of metallic glass become important only for embossing of features with diameters below 500 nm (second and third terms in equation 1). Instead, the inventors use embossing for microscale features (diameters≧20 μm, aspect-ratio ˜2-3) and subsequent template free elongation for nanofabrication. The microscale embossing step is essentially unaffected by the wetting and the oxidation properties of metallic glasses. The size reduction to nanoscale regime occurs during out of template stretching where the contact angle is unimportant and the uniaxial tensile stress required to break the oxide shell remains independent of feature diameter. This has been a major roadblock for nanoscale embossing of oxidizing alloys because the stress required to break the oxide layer scales inversely with the square of feature diameter. The oxidation can still affect the surface roughness during elongation (magnified SEM images in
The present invention provides a versatile method to fabricate very high aspect-ratio metallic glass nanostructures assembled on various substrates. Arrays of metallic glass microfeatures are reshaped into nanostructures (solid and hollow) by controlled elongation and rupture in the supercooled liquid state. The inventors utilize Newtonian and non-Newtonian effects in metallic glass supercooled liquids to tune the shape and size of structures during extensional flow and final fracture. This approach eliminates the fundamental constraints of nanoscale embossing: rising pressure with aspect-ratio, expensive nanotemplates, limited to inert compositions, and inability to produce unsupported nanostructures. As demonstrated here, the drawing approach is capable of generating nanostructures from oxidation prone glass formers without using nanotemplates. It also creates an additional set of nanostructures detached from the metallic glass substrate after fracture. This extra set of nanostructures can be anchored on various templates or released in free form. In particular, the ability to produce metallic glass nanostructures on insulating substrates (quartz and polymer) can allow characterization of size dependent thermal and electrical properties. Such studies have been rare in the past due to difficulty in producing metallic glass nanostructures separated from the conductive base73. Besides scientific interests, the assembled nanostructures shown here can also enable many practical applications for metallic glasses such as electrodes, sensors, microfluidics, flexible electronics, conductive probes for atomic force microscopy, and micro-needles for drug delivery. Although, the focus of this work was on metallic glasses, the parallel drawing technique can be extended to other thermoplastic materials.
Thermoplastic embossing of metallic glasses promises direct imprinting of metal nanostructures using templates. However, embossing high-aspect-ratio nanostructures faces unworkable flow resistance due to friction, and non-wetting conditions, at the template interface. Here, the inventors show that these inherent challenges of embossing can be reversed by thermoplastic drawing from templates. The flow resistance not only remains independent of wetting but also decreases with increasing feature aspect-ratio. Arrays of assembled nano-tips, nano-wires, and nano-tubes with aspect-ratios exceeding 1000 can be produced through controlled elongation and fracture of metallic glass structures. In contrast to embossing, the drawing approach generates two sets of nanostructures upon final fracture; one set remains anchored to the metallic glass substrate while the second set is assembled on the template. This method can be readily adapted for high-throughput fabrication and testing of nanoscale tensile specimens, enabling rapid screening of size-effects in mechanical behavior.
Thermoplastic replication of templates by hot-pressing of metallic glasses is well-established for fabrication of patterned surfaces. Above glass transition temperature, the metallic glasses become soft and flow into template cavities when subjected to pressure. Subsequently, the templates are cooled to room temperature and dissolved in chemicals to separate the metallic glasses. Due to thermal expansion mismatch and roughness of template cavities, the metallic glasses cannot be non-destructively detached, which limits the template use to a single operation. To overcome this issue, the present invention separates the metallic glass and the templates by controlled pulling when the metallic glass is still hot and soft. Depending on the temperature (viscosity), adhesion, and the pulling speed (strain-rate), the metallic glass structures can either demold from templates or get deformed into a rich variety of nanostructures. The shape and size of micro- and nanostructures can also be controlled by initial geometry of template features. This provides a versatile micro- and nanofabrication method for metallic glasses without resourcing to expensive nano-templates or disposable micro-templates.
Thermoplastic molding is the most economical fabrication method for small-scale metallic glass structures because machining is not suitable for such hard materials. The method works very well for micro-scale or larger structures with low aspect-ratios. Prior to the present invention, fabrication of nano-scale features with high-aspect ratios becomes difficult due to capillary pressure and template friction. The novelty of the present invention is that it can create nano-scale features with high-aspect-ratios by simple mechanical elongation of micro-scale features. This process is independent of capillary pressure and template friction because the nano-scale feature creation takes place out of templates.
Conventional nanomolding of metallic glasses produces only metallic surfaces patterned with nano-scale features. In contrast, the present invention generates patterned surfaces and free-standing metallic glass nanostructures simultaneously. In addition, the free-standing metallic glass nanostructures produced are already fixed on templates and therefore do not require any additional assemblage. The initial shape of template features provides an additional control parameter for tuning the final shape of metallic glass nanostructures. Excellent surface finish, uniform shape, and controllable aspect-ratio metallic glass nanostructures can be produced without using expensive nano-templates.
The method of the present invention can be used to form high-surface area wires for catalysts and sensors, electrodes such as neural implants, fuel cells electrodes, metal templates for nanoimprinting, inexpensive patterning of metallic glasses using reusable templates, conductive tips for scanning probe microscopy, for use in the silicon integrated circuit industry, energy industry, microneedles for drug delivery, implantable sensors industry and consumer electronics.
It is to be understood that the present invention is not limited in its application to the details of the order or sequence, and number, of steps or procedures, sub-steps or sub-procedures, of operation or implementation of the method for producing (fabricating) an array of nanoscale structures on a substrate surface, via a self-assembled template, or to the details of the equipment, chemical reagents, and materials, used for implementing the method, set forth in the following illustrative description, accompanying drawings, and examples, unless otherwise specifically stated herein. The present invention is capable of other embodiments and of being practiced or carried out in various ways. Although steps or procedures, sub-steps or sub-procedures, equipment, chemical reagents, and materials, which are equivalent or similar to those illustratively described herein can be used for practicing or testing the present invention, suitable steps or procedures, sub-steps or sub-procedures, equipment, chemical reagents, and materials, are illustratively described and exemplified herein.
It is also to be understood that all technical and scientific words, terms, or/and phrases, used herein throughout the present disclosure have either the identical or similar meaning as commonly understood by one of ordinary skill in the art to which this invention belongs, unless otherwise specifically defined or stated herein. Phraseology, terminology, and, notation, employed herein throughout the present disclosure are for the purpose of description and should not be regarded as limiting. Moreover, all technical and scientific words, terms, or/and phrases, introduced, defined, described, or/and exemplified, in the above Background section, are equally or similarly applicable in the illustrative description of the preferred embodiments, examples, and appended claims, of the present invention. Immediately following are definitions and exemplary usages of words, terms, or/and phrases, which are used throughout the illustrative description of the preferred embodiments, examples, and appended claims, of the present invention, and are especially relevant for understanding thereof. The term ‘producing’, and grammatical forms thereof, as used herein, are considered synonymous and equivalent to the following terms, and corresponding grammatical forms thereof: ‘fabricating’, ‘making’, ‘creating’, ‘constructing’, and ‘manufacturing’.
It will be understood that particular embodiments described herein are shown by way of illustration and not as limitations of the invention. The principal features of this invention can be employed in various embodiments without departing from the scope of the invention. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, numerous equivalents to the specific procedures described herein. Such equivalents are considered to be within the scope of this invention and are covered by the claims.
All publications and patent applications mentioned in the specification are indicative of the level of skill of those skilled in the art to which this invention pertains. All publications and patent applications are herein incorporated by reference to the same extent as if each individual publication or patent application was specifically and individually indicated to be incorporated by reference.
The use of the word “a” or “an” when used in conjunction with the term “comprising” in the claims and/or the specification may mean “one,” but it is also consistent with the meaning of “one or more,” “at least one,” and “one or more than one.” The use of the term “or” in the claims is used to mean “and/or” unless explicitly indicated to refer to alternatives only or the alternatives are mutually exclusive, although the disclosure supports a definition that refers to only alternatives and “and/or.” Throughout this application, the term “about” is used to indicate that a value includes the inherent variation of error for the device, the method being employed to determine the value, or the variation that exists among the study subjects.
As used in this specification and claim(s), the words “comprising” (and any form of comprising, such as “comprise” and “comprises”), “having” (and any form of having, such as “have” and “has”), “including” (and any form of including, such as “includes” and “include”) or “containing” (and any form of containing, such as “contains” and “contain”) are inclusive or open-ended and do not exclude additional, unrecited elements or method steps.
The term “or combinations thereof” as used herein refers to all permutations and combinations of the listed items preceding the term. For example, “A, B, C, or combinations thereof” is intended to include at least one of: A, B, C, AB, AC, BC, or ABC, and if order is important in a particular context, also BA, CA, CB, CBA, BCA, ACB, BAC, or CAB. Continuing with this example, expressly included are combinations that contain repeats of one or more item or term, such as BB, AAA, AB, BBC, AAABCCCC, CBBAAA, CABABB, and so forth. The skilled artisan will understand that typically there is no limit on the number of items or terms in any combination, unless otherwise apparent from the context.
All of the compositions and/or methods disclosed and claimed herein can be made and executed without undue experimentation in light of the present disclosure. While the compositions and methods of this invention have been described in terms of preferred embodiments, it will be apparent to those of skill in the art that variations may be applied to the compositions and/or methods and in the steps or in the sequence of steps of the method described herein without departing from the concept, spirit and scope of the invention. All such similar substitutes and modifications apparent to those skilled in the art are deemed to be within the spirit, scope and concept of the invention as defined by the appended claims.
This application claims priority to U.S. Provisional Application Ser. No. 62/333,901, filed May 10, 2016, the entire contents of which are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 62333901 | May 2016 | US |
