Patent Application
20180244518
One goal of modern materials science involves the production of macro-scale structures from micro-scale elements having dimensions on the order of microns or nanometers. Such structures may be tailored to have novel mechanical, electrical, and optical properties that are unobtainable using conventional manufacturing techniques. Conventional micro-scale manufacturing processes, for example, as used in the semiconductor industry are incapable of producing macro-scale structures from micro-scale elements. For example, conventional semiconductor manufacturing equipment and processes are incapable of producing micro-scale elements having aspect ratios much greater than about 50:1 or about 100:1. Conventional additive manufacturing equipment and processes (often referred to as “3-D printing”) are incapable of producing objects having dimensions on the order of microns or nanometers and are incapable of quickly producing macro-scale structures from micro-scale elements.
In accordance with an aspect disclosed herein, there is provided a method of assembly of micro/nano-scale objects into a three dimensional structure. The method comprises forming a pattern of a first functional moiety on a surface of a substrate, contacting the surface of the substrate with a first liquid suspension including first micro/nano-scale feedstock elements functionalized with a second functional moiety, complimentary to the first functional moiety, on first portions of the first micro/nano-scale feedstock elements and functionalized with a third functional moiety on second portions of the first micro/nano-scale feedstock elements, aligning the first portions of the first micro/nano-scale feedstock elements in the first liquid suspension with the surface of the substrate, and facilitating bonding the second functional moieties to the first functional moieties to form a first mesostructure pattern of the first micro/nano-scale feedstock elements on the surface of the substrate. The method further comprises contacting the first mesostructure pattern of the first micro/nano-scale feedstock elements on the surface of the substrate with a second liquid suspension including micro/nano-scale linker feedstock elements functionalized with a fourth functional moiety, complimentary to the third functional moiety, on first portions of the micro/nano-scale linker feedstock elements and functionalized with a fifth functional moiety on second portions of the micro/nano-scale linker feedstock elements, aligning the first portions of the micro/nano-scale linker feedstock elements in the second liquid suspension with the second portions of a first group of the first micro/nano-scale feedstock elements, and facilitating bonding the fourth functional moieties to the third functional moieties to form a second mesostructure of micro/nano-scale objects on the surface of the substrate. The method further comprises contacting the second mesostructure pattern of micro/nano-scale feedstock elements on the surface of the substrate with a third liquid suspension including second micro/nano-scale feedstock elements functionalized with a sixth functional moiety, complimentary to the fifth functional moiety, on first portions of the second micro/nano-scale feedstock elements and functionalized with a seventh functional moiety, on second portions of the second micro/nano-scale feedstock elements, aligning the first portions of the second micro/nano-scale feedstock elements in the third liquid suspension with the second portions of a first group of the micro/nano-scale linker feedstock elements, aligning the second portions of the second micro/nano-scale feedstock elements in the third liquid suspension with the second portions of a second group of the micro/nano-scale linker feedstock elements, and facilitating bonding the sixth and seventh functional moieties to the fifth functional moieties to form the three-dimensional structure of micro/nano-scale objects on the surface of the substrate.
In some embodiments, facilitating bonding the fourth functional moieties to the third functional moieties and facilitating bonding the sixth and seventh functional moieties to the fifth functional moieties includes leaving some of at least one of the fourth, fifth, sixth, or seventh functional moieties unbonded.
In some embodiments, the method further comprises contacting the three dimensional structure of micro/nano-scale objects with a third liquid suspension including third micro/nano-scale feedstock elements, aligning and positioning first portions of the third micro/nano-scale feedstock elements in the third liquid suspension with third portions of the second micro/nano-scale feedstock elements, and facilitating bonding the first portions of third micro/nano-scale feedstock elements to the third portions of the second micro/nano-scale feedstock elements.
In some embodiments, the first portions of the third micro/nano-scale feedstock elements are bonded to the third portions of the second micro/nano-scale feedstock elements with complimentary click chemical groups.
In some embodiments, portions of micro/nano-scale feedstock elements are bonded to portions of other micro/nano-scale feedstock elements with complimentary click chemical groups.
In some embodiments, the first portions of third micro/nano-scale feedstock elements are bonded to the third portions of the second micro/nano-scale feedstock elements with complimentary DNA strands.
In some embodiments, portions of micro/nano-scale feedstock elements are bonded to portions of other micro/nano-scale feedstock elements with complimentary DNA strands.
In some embodiments, aligning and positioning the first portions of the third micro/nano-scale feedstock elements with the third portions of the second micro/nano-scale feedstock elements includes aligning and positioning the first portions of the third micro/nano-scale feedstock elements with the third portions of the second micro/nano-scale feedstock elements with an electric field to create electrophoretic and/or dielectrophoretic forces.
In some embodiments, aligning and positioning portions of micro/nano-scale feedstock elements with portions of other micro/nano-scale feedstock elements includes aligning and positioning the portions of the micro/nano-scale feedstock elements with the portions of the other micro/nano-scale feedstock elements with an electric field to create electrophoretic and/or dielectrophoretic forces.
In some embodiments, aligning and positioning the first portions of the third micro/nano-scale feedstock elements with the third portions of the second micro/nano-scale feedstock elements includes aligning and positioning the first portions of the third micro/nano-scale feedstock elements with the third portions of the second micro/nano-scale feedstock elements utilizing flow of fluid in the third liquid suspension.
In some embodiments, aligning and positioning portions of micro/nano-scale feedstock elements with portions of other micro/nano-scale feedstock elements includes aligning and positioning the portions of the micro/nano-scale feedstock elements with the portions of the other micro/nano-scale feedstock elements utilizing flow of fluid in the third liquid suspension.
In some embodiments, aligning and positioning the first portions of the third micro/nano-scale feedstock elements with the third portions of the second micro/nano-scale feedstock elements includes aligning and positioning the first portions of the third micro/nano-scale feedstock elements with the third portions of the second micro/nano-scale feedstock elements utilizing a magnetic field.
In some embodiments, aligning and positioning portions of micro/nano-scale feedstock elements with portions of other micro/nano-scale feedstock elements includes aligning and positioning the portions of the micro/nano-scale feedstock elements with the portions of the other micro/nano-scale feedstock elements utilizing a magnetic field.
In some embodiments, aligning and positioning the first portions of the third micro/nano-scale feedstock elements with the third portions of the second micro/nano-scale feedstock elements includes aligning and positioning the first portions of the third micro/nano-scale feedstock elements with the third portions of the second micro/nano-scale feedstock elements utilizing optical trapping.
In some embodiments, aligning and positioning portions of micro/nano-scale feedstock elements with portions of other micro/nano-scale feedstock elements includes aligning and positioning the portions of the micro/nano-scale feedstock elements with the portions of the other micro/nano-scale feedstock elements utilizing optical trapping.
In some embodiments, the method further comprises contacting the three dimensional structure of micro/nano-scale objects with a fourth liquid suspension including one or more of nanotubes, nanorods, and nanoparticles, aligning and positioning first portions of the one or more of nanotubes, nanorods, and nanoparticles in the fourth liquid suspension with second portions of the third micro/nano-scale feedstock elements, and bonding the one or more of nanotubes, nanorods, and nanoparticles to the second portions of the third micro/nano-scale feedstock elements with complimentary chemical groups, for example, complimentary click chemical groups and/or complimentary DNA strands.
In some embodiments, one or more of the first, second, or third micro/nano-scale feedstock elements include one or more of nanotubes, nanorods, or nanoparticles.
In some embodiments, the one or more of nanotubes, nanorods, and nanoparticles comprise one of carbon nanotubes, nanorods, and nanoparticles, boron nanotubes, nanorods, and nanoparticles, or combinations thereof.
In some embodiments, the one or more of nanotubes, nanorods, and nanoparticles are bonded to the second portions of the third micro/nano-scale feedstock elements with complimentary click chemical groups.
In some embodiments, the one or more of nanotubes, nanorods, and nanoparticles are bonded to portions of other micro/nano-scale feedstock elements with complimentary click chemical groups.
In some embodiments, the one or more of nanotubes, nanorods, and nanoparticles are bonded to the second portions of the third micro/nano-scale feedstock elements with complimentary DNA strands.
In some embodiments, the one or more of nanotubes, nanorods, and nanoparticles are bonded to portions of other micro/nano-scale feedstock elements with complimentary DNA strands.
In some embodiments, aligning and positioning the first portions of the one or more of carbon nanotubes, nanorods, and nanoparticles with the second portions of the third micro/nano-scale feedstock elements includes aligning and positioning the first portions of the one or more of nanotubes, nanorods, and nanoparticles with the second portions of the third micro/nano-scale feedstock elements with an electric field to create electrophoretic and/or dielectrophoretic forces.
In some embodiments, aligning and positioning the portions of the one or more of carbon nanotubes, nanorods, and nanoparticles with portions of other micro/nano-scale feedstock elements includes aligning and positioning the portions of the one or more of nanotubes, nanorods, and nanoparticles with the portions of the other micro/nano-scale feedstock elements with an electric field to create electrophoretic and/or dielectrophoretic forces.
In some embodiments, the method further comprises concurrently bonding at least two of i) the first portions of the first micro/nano-scale feedstock elements to the substrate, ii) the second portions of the first group of the first micro/nano-scale feedstock elements to the first portions of the second micro/nano-scale feedstock elements, iii) the second portions of the second group of the first micro/nano-scale feedstock elements to the second portions of the second micro/nano-scale feedstock elements, iv) the first portions of the third micro/nano-scale feedstock elements to the third portions of the second micro/nano-scale feedstock elements, and v) the one or more of nanotubes, nanorods, and nanoparticles to the second portions of the third micro/nano-scale feedstock elements or the one or more of nanotubes, nanorods, and nanoparticles to portions of other micro/nano-scale feedstock elements.
In some embodiments, the third functional moiety is the same as the first functional moiety.
In some embodiments, the fourth functional moiety is the same as the second functional moiety.
In some embodiments, the third functional moiety is the same as the second functional moiety.
In some embodiments, the fourth functional moiety is the same as the first functional moiety.
In some embodiments, facilitating bonding the second functional moieties to the first functional moieties includes initiating bonding between the second functional moieties and the first functional moieties by one of application of thermal energy to the second functional moieties and/or the first functional moieties, application of radiation to the second functional moieties and/or the first functional moieties, exposing the second functional moieties and/or the first functional moieties to a chemical catalyst and/or by changing a pH of the first fluid suspension to facilitate bonding between the first and second functional moieties.
In some embodiments, facilitating bonding between complimentary functional moieties includes initiating bonding between the complimentary functional moieties by one of application of thermal energy to the complimentary functional moieties, application of radiation to the complimentary functional moieties, exposing the complimentary functional moieties to a chemical catalyst and/or by changing a pH of a fluid suspension in which the complimentary functional moieties are immersed.
In some embodiments, the method further comprises bonding the first functional moiety with a linker molecule to an adhesion element bonded to the surface of the substrate to form the pattern of the first functional moiety on the surface of the substrate.
In some embodiments, the adhesion element comprises one or more of a metal, silicon, and silicon dioxide.
In some embodiments, the method further comprises bonding the second functional moiety with a linker molecule to an adhesion element bonded to the first portion of the first micro/nano-scale feedstock element.
In some embodiments, the method further comprises bonding functional moieties with linker molecules to adhesion elements bonded to portions of micro/nano-scale feedstock elements.
In some embodiments, the method further comprises facilitating bonding a plurality of the second micro/nano-scale feedstock elements to the second portions of each of the first micro/nano-scale feedstock elements.
In some embodiments, the method further comprises facilitating bonding a plurality of micro/nano-scale feedstock elements to portions of single other micro/nano-scale feedstock elements.
In some embodiments, the method further comprises facilitating bonding a plurality of the first micro/nano-scale feedstock elements to individual bonding sites including the first functional moiety on the surface of a substrate.
In some embodiments, facilitating bonding the second functional moieties to the first functional moieties includes facilitating bonding a first click chemical group to a complimentary click chemical group.
In some embodiments, facilitating bonding the second functional moieties to the first functional moieties includes facilitating bonding a first DNA strand to a complimentary DNA strand.
In some embodiments, the method further comprises bonding the first micro/nano-scale feedstock elements to the surface of the substrate with an additional bonding mechanism.
In some embodiments, the method further comprises forming at least one of the first, second, and third micro/nano-scale feedstock elements by sequential infiltration synthesis of a domain of a block copolymer.
In some embodiments, the method further comprises forming micro/nano-scale feedstock elements by sequential infiltration synthesis of a domain of a block copolymer.
In some embodiments, the method further comprises forming at least one of the first, second, or third micro/nano-scale feedstock elements by a method comprising depositing a liquid phase block copolymer into an area defined on or in an upper layer of a multi-layer substrate, annealing the block copolymer to facilitate separation of the block copolymer into multiple aligned polymer domains, removing one of the polymer domains, etching through a remaining polymer domain and into the upper layer of the multi-layer substrate, and obtaining the at least one of the first, second, or third micro/nano-scale feedstock elements by separating etched portions of the upper layer of the multi-layer substrate from a second layer of the multi-layer substrate.
In some embodiments, the method further comprises forming micro/nano-scale feedstock elements by a method comprising depositing a liquid phase block copolymer into an area defined on or in an upper layer of a multi-layer substrate, annealing the block copolymer to facilitate separation of the block copolymer into multiple aligned polymer domains, removing one of the polymer domains, etching through a remaining polymer domain and into the upper layer of the multi-layer substrate, and obtaining micro/nano-scale feedstock elements by separating etched portions of the upper layer of the multi-layer substrate from a second layer of the multi-layer substrate.
In some embodiments, the method further comprises forming at least one of the first, second, or third micro/nano-scale feedstock elements by a method comprising depositing a liquid phase block copolymer into an area defined on or in an upper layer of a multi-layer substrate, annealing the block copolymer to facilitate separation of the block copolymer into multiple aligned polymer domains, converting one of the polymer domains into an inorganic material using sequential infiltration synthesis, removing one of the polymer domains, etching through a second of the polymer domains and into the upper layer of the multi-layer substrate using the inorganic material as an etch mask, and obtaining the at least one of the first, second, or third micro/nano-scale feedstock elements by separating etched portions of the upper layer of the multi-layer substrate from a second layer of the multi-layer substrate.
In some embodiments, the method further comprises forming micro/nano-scale feedstock elements by a method comprising depositing a liquid phase block copolymer into an area defined on or in an upper layer of a multi-layer substrate, annealing the block copolymer to facilitate separation of the block copolymer into multiple aligned polymer domains, converting one of the polymer domains into an inorganic material using sequential infiltration synthesis, etching through a second of the polymer domains and into the upper layer of the multi-layer substrate using the inorganic material as an etch mask, and obtaining the micro/nano-scale feedstock elements by separating etched portions of the upper layer of the multi-layer substrate from a second layer of the multi-layer substrate.
In some embodiments, the method further comprises, prior to separating the etched portions of the upper layer of the multi-layer substrate from the second layer of the multi-layer substrate, depositing and patterning a layer of photoresist on the micro/nano-scale feedstock elements, patterning of the layer of photoresist exposing portions of the micro/nano-scale feedstock elements, defining lengths of the micro/nano-scale feedstock elements by etching through exposed portions of the micro/nano-scale feedstock elements, functionalizing exposed end portions of the micro/nano-scale feedstock elements while the micro/nano-scale feedstock elements are embedded in the photoresist, and removing the photoresist.
In some embodiments, forming at least one of the first, second, or third micro/nano-scale feedstock elements includes forming at least one of the first micro/nano-scale feedstock elements with at least one dimension smaller than about 50 nm.
In some embodiments, forming at least one of the first, second, or third micro/nano-scale feedstock elements includes forming at least one of the first micro/nano-scale feedstock elements with at least one dimension smaller than about 5 nm.
In some embodiments, forming micro/nano-scale feedstock elements includes forming micro/nano-scale feedstock elements with at least one dimension between about 5 nm and about 50 nm.
In some embodiments, the method further comprises functionalizing the first micro/nano-scale feedstock elements with the second functional moiety by a method including depositing a first bonding material on the second portions of the first micro/nano-scale feedstock elements, and exposing the first bonding material to a multifunctional click chemical including a chemical group having an affinity for the first bonding material.
In some embodiments, the method further comprises functionalizing micro/nano-scale feedstock elements with functional moieties by a method including depositing a first bonding material on portions of the micro/nano-scale feedstock elements, and exposing the first bonding material to a multifunctional click chemical including a chemical group having an affinity for the first bonding material.
In some embodiments, depositing the first bonding material on the second portions of the first micro/nano-scale feedstock elements includes depositing one of gold, silicon, and silicon dioxide on the second portions of the first micro/nano-scale feedstock elements.
In some embodiments, depositing the first bonding material on the portions of the micro/nano-scale feedstock elements includes depositing one of gold, silicon, and silicon dioxide on the portions of the micro/nano-scale feedstock elements.
In some embodiments, exposing the first bonding material to the multifunctional click chemical includes exposing the first bonding material to a chemical including the chemical group having the affinity for the first bonding material, an intermediate chemical group bonded to the chemical group having the affinity for the first bonding material and a further chemical group having an affinity for a second bonding material.
In some embodiments, the intermediate chemical group comprises a polymer chain.
In accordance with another aspect, there is provided a method of assembly of micro/nano-scale objects into a three dimensional lattice or truss structure. The method comprises forming a first liquid suspension including first micro/nano-scale feedstock elements functionalized with a first functional moiety on first portions of the first micro/nano-scale feedstock elements and linker elements including a second functional moiety, complimentary to the first functional moiety, on first portions of the linker elements and a third functional moiety on second portions of the linker elements, aligning the first portions of the first micro/nano-scale feedstock elements in the first liquid suspension with the first portions of the linker elements, facilitating bonding the second functional moieties to the first functional moieties to bond the linker elements to the first portions of the first micro/nano-scale feedstock elements, contacting the first micro/nano-scale feedstock elements and linker elements with a second liquid suspension including second micro/nano-scale feedstock elements functionalized with a fourth functional moiety, complimentary to the third functional moiety, on first portions of the second micro/nano-scale feedstock elements and on second portions of the second micro/nano-scale feedstock elements, aligning the first portions of the second micro/nano-scale feedstock elements in the second liquid suspension with the second portions of a first group of the linker elements, aligning the second portions of the second micro/nano-scale feedstock elements in the second liquid suspension with the second portions of a second group of the linker elements, and facilitating bonding the fourth functional moieties to the third functional moieties to form the three dimensional lattice or truss structure.
In some embodiments, the method further comprises contacting the three dimensional lattice or truss structure with a third liquid suspension including third micro/nano-scale feedstock elements functionalized with a fifth functional moiety, complimentary to a sixth functional moiety on a third portion of at least a portion of the linker elements, on first portions of the third micro/nano-scale feedstock elements, aligning the first portions of the third micro/nano-scale feedstock elements in the third liquid suspension with the third portions of the at least a portion of the linker elements, and facilitating bonding the fifth functional moieties to the sixth functional moieties.
In some embodiments, the method comprises aligning the first, second, and third micro/nano-scale feedstock elements into an auxetic truss structure.
In accordance with another aspect, there is provided a three dimensional lattice or truss structure of micro/nano-scale objects. The structure comprises a plurality of first micro/nano-scale feedstock elements having first portions bonded to first portions of linker elements and a plurality of second micro/nano-scale feedstock elements having first portions bonded to second portions of the linker elements and second portions bonded to third portions of the linker elements.
In some embodiments, the first portions of the plurality of first micro/nano-scale feedstock elements are bonded to the first portions of the linker elements with click chemical bonds.
In some embodiments, at least a portion of one of the first micro/nano-scale feedstock elements and the second micro/nano-scale feedstock elements have length:width aspect ratios of at least about 20:1.
In some embodiments, the structure further comprises a plurality of the second micro/nano-scale feedstock elements bonded to each first micro/nano-scale feedstock element.
In some embodiments, the structure further comprises a plurality of third micro/nano-scale feedstock elements having first portions bonded to fourth portions of the linker elements.
In some embodiments, the first portions of the plurality of third micro/nano-scale feedstock elements are bonded to fourth portions of the linker elements with click chemical bonds.
In some embodiments, the first, second, and third micro/nano-scale feedstock elements are arranged into an auxetic truss.
In some embodiments, the structure further comprises a plurality of the third micro/nano-scale feedstock elements bonded to each second micro/nano-scale feedstock element.
In accordance with another aspect, there is provided a method of assembly of micro/nano-scale objects into a three dimensional structure. The method comprises forming a pattern of a first functional moiety on a surface of a substrate, contacting the surface of the substrate with a first liquid suspension including first micro/nano-scale feedstock elements functionalized with a second functional moiety, complimentary to the first functional moiety, on first portions of the first micro/nano-scale feedstock elements and functionalized with a third functional moiety on second portions of the first micro/nano-scale feedstock elements, aligning the first portions of the first micro/nano-scale feedstock elements in the first liquid suspension with the surface of the substrate, facilitating bonding the second functional moieties to the first functional moieties to form a first mesostructure pattern of the first micro/nano-scale feedstock elements on the surface of the substrate, contacting the first mesostructure pattern of the first micro/nano-scale feedstock elements on the surface of the substrate with a second liquid suspension including second micro/nano-scale feedstock elements functionalized with a fourth functional moiety, complimentary to the third functional moiety, on first portions of the second micro/nano-scale feedstock elements and on second portions of the second micro/nano-scale feedstock elements, aligning the first portions of the second micro/nano-scale feedstock elements in the second liquid suspension with the second portions of a first group of the first micro/nano-scale feedstock elements, aligning the second portions of the second micro/nano-scale feedstock elements in the second liquid suspension with the second portions of a second group of the first micro/nano-scale feedstock elements, and facilitating bonding the fourth functional moieties to the third functional moieties to form the three dimensional structure of micro/nano-scale objects on the surface of the substrate.
In some embodiments, facilitating bonding the fourth functional moieties to the third functional moieties includes facilitating bonding the fourth functional moieties to linker elements and facilitating bonding of the linker elements to the third functional moieties.
The accompanying drawings are not intended to be drawn to scale. In the drawings, each identical or nearly identical component that is illustrated in various figures is represented by a like numeral. For purposes of clarity, not every component may be labeled in every drawing. In the drawings:
Aspects and embodiments disclosed herein are not limited in application to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. Aspects and embodiments disclosed herein are capable of being practiced or of being carried out in various ways. Also, the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” “having,” “containing,” “involving,” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items.
Aspects and embodiments disclosed herein are generally directed to the formation of novel macro-scale structures from micro-scale or nano-scale elements having dimensions on the order of microns or nanometers. The disclosed macro-scale structures have mechanical, electrical, thermal, and/or optical properties that are unobtainable using conventional manufacturing techniques. Aspects and embodiments disclosed herein include the formation of macro-scale objects from micro-scale or nano-scale elements using a combination of directed fluidic assembly and “click” chemistry and/or DNA selective assembly techniques. Although the term “micro-scale elements” is used herein, it should be understood that the feedstock elements or other structures described herein are not limited to having dimensions of a micron or greater. The term “micro-scale elements” also encompasses feedstock elements or other structures having characteristic dimensions (length, width, etc.) smaller than one micron, for example, as small as less than about 1 nanometer. The term “micro-scale elements” or variations thereof is used synonymously with the term “micro/nano-scale elements” and variations thereof.
Directed Fluidic Assembly (DFA) is an assembly method that allows structures made by dissimilar methods to be assembled together. It can be combined with planar micro/nanofabrication, micro-machining, 3D printing, and other fabrication modalities. DFA provides for rapid placement of homogeneous or heterogeneous feedstock onto a substrate or to other feedstock elements with controlled position and orientation. An advantage of DFA lies in the ability to use optimal methods to fabricate individual micro/nano components and assemble them into a permanently-bonded functional mechanical, electrical, thermal, fluidic, and/or thermal system. In some implementations DFA assembly is rapid: a feedstock spacing of 5 μm over a 100 mm wafer with a 2-minute assembly time corresponds to a rate of 2.5 million objects bonded per second. Smaller feedstocks will assemble at even higher rates.
Aspects and embodiments disclosed herein utilize a DFA technique for directed fluidic assembly of submicron to tens-of-micron-scale objects (feedstock) into millimeter-scale or larger structures (macro-scale structures). In some embodiments, high-aspect-ratio micro/nanofabricated feedstock structures of the same or of different length scales are fabricated in the plane of a substrate, released, and then combined by DFA into multiscale structures that have high aspect ratios perpendicular to a substrate or into three dimensional lattice or truss structures. In some embodiments, bonds to and between feedstock elements are permanent and provide for electrical conduction, thermal conduction, and/or optical transmission as required by the assembled system.
In some embodiments, DFA techniques for assembling micro-scale elements into larger composite structures include methods utilizing dielectrophoresis, electrophoresis, directed fluid flow, convection, capillary forces, magnetic fields, diffusion, optical trapping, or combinations thereof for orienting and positioning the micro-scale elements during fabrication. Many approaches have been used to assemble particles and other micro and nano building blocks onto conductive or insulating surfaces or structures. The control and speed of the assembly depends on many parameters, for example, particle size, concentration, charge, flow speed and direction, voltage, frequency, dielectric constant, etc. When using assembly mechanisms that depend on fluidic, capillary or other forces, the assembly forces, although controlled, can not be turned on and off (on demand) as in dielectrophoresis (DEP) or electrophoresis (EP) based assembly. Electrophoresis is a directed assembly method for fast assembly but it requires micro-scale elements to be oriented during a fabrication process to have a charge. DEP assembly forces depend only on the dielectric constant of the particle or the feedstock and therefore are more suitable for use to assemble uncharged feedstock. DEP assembly may be used to assemble nano and micro scale particles, rods or bars, and/or nanotube bundles into two and three-dimensional structures in seconds over a large area with precise alignment at desired locations. Based on the dilution of the feedstock solution and the strength of the applied electric field one can control the rate of assembly. Since the DEP force polarizes the feedstock, it leads to alignment of feedstock to orient the feedstock during assembly. Directionality of the nanomaterials as well as nanoscale feedstocks during assembly can effectively be controlled by controlling the applied electric field lines/gradients. The DEP assembly force can be effectively applied at the nano or microscale.
An embodiment of a DFA process 200 for fabricating an array of objects from two layers of micro-scale elements is shown schematically in
In act 210 of
In act 215 of
In act 225 of
In act 230 of
In accordance with process 200, additional layers of feedstock material may be added to previously bonded micro-scale feedstock elements until a desired number of layers is reached to form a desired macro-scale object (act 240 of
By patterning the substrate and faces or ends of the feedstock with click chemicals, 2-D and 3-D structures may be created. By patterning click chemicals on specific locations on the faces, ends, or portions of the sides of the feedstock, different layers of feedstock elements may be oriented at any desired orientation relative to each other. DFA is a rapid and scalable manufacturing technique due to its parallel nature. However, compared to some slower pick-and-place manufacturing techniques, DFA may suffer from defects, and thus may be best suited for defect-tolerant applications. For less defect tolerant structures, DFA could be combined with error-checking and/or pick-and-place correction techniques to achieve low defect levels at high fabrication rates.
Micro-scale feedstock elements utilized in forming 2-D and 3-D structures disclosed herein may be formed from materials including, for example, silicon, silicon dioxide, silicon nitride, silicon carbide, alumina, titania, zinc oxide, tungsten, SU-8 photoresist or other organic or inorganic polymers, biologically-based materials, for example, chitosan, or other materials selected based on, for example, desired mechanical, thermal, optical, electrical, magnetic, and/or chemical properties.
Micro-scale feedstock elements utilized in forming 2-D and 3-D structures disclosed herein may be formed using processes similar to those used in the fabrication of electronic devices in the semiconductor industry and/or micro electro mechanical system (MEMS) devices. One example of a method 400 for forming micro-scale feedstock elements utilized in forming 2-D and 3-D structures disclosed herein is described in the flowchart of
In act 405, a substrate, for example, a silicon wafer 305 (or alternatively, sapphire, a glass wafer, a piezoelectric material, quartz or another insulator, or another substrate material desired for a particular implementation) is provided and a sacrificial layer of dielectric 310 for example, silicon dioxide (SiO2) or silicon nitride (Si3N4 (which may be utilized when forming a feedstock element from SiO2)) is grown on the face of the silicon wafer 305 using a chemical vapor deposition (CVD) or diffusion process in a diffusion furnace as known in the semiconductor fabrication arts (See
In act 410 (
In act 415, the layer 315 of the feedstock material is patterned. Patterning of the layer 315 of the feedstock material may be accomplished using known methods of patterning of features on a semiconductor wafer. For example, a layer of photoresist 320 may be deposited conformally over the layer 315 of the feedstock material by spin coating and prebaked to drive off excess photoresist solvent. (
In act 420 a second layer of photoresist 330 is then deposited on the micro-scale feedstock elements 325 and patterned such that only portions of the feedstock elements 325 that are desired to be functionalized are exposed. (
In act 425 an adhesion material 340 to which a click chemical group and associated binder molecule is later to be bonded is deposited on the exposed portions of the feedstock elements 325. (
In other embodiments, the material 340 deposits conformally over the second layer of photoresist 330, the exposed portions of the feedstock elements 325, and the exposed surface of dielectric layer 310, in which instance a further photoresist layer may be deposited to cover the portions of the feedstock elements 325 onto which the material 340 was deposited and expose the surface of dielectric layer 310 on which the material 340 was deposited so that the material 340 may be etched off of the surface of dielectric layer 310 on which the material 340 was deposited, for example, with a wet etch. The further layer of photoresist would then be removed. Alternatively or additionally, material 340 deposited on the exposed surface of dielectric layer 310 may be removed with an anisotropic dry etch (for example, an argon plasma etch) with or without providing a layer of photoresist to protect the ends of the feedstock elements 325 onto which the material 340 was deposited. (See
In act 430, the second layer of photoresist 330 is removed, for example, by thermal decomposition and/or chemical dissolution. Portions of the material 340 adhered to the second layer of photoresist 330 may also be removed in this act, resulting in the feedstock element layer 315 including the material 340 attached to the feedstock elements remaining on the layer of dielectric 310. (
In act 435, the micro-scale feedstock elements 325 are released from the wafer 305 by dissolving or etching away the dielectric layer 310 by exposure to a wet etching agent 345, for example, hydrofluoric acid if the dielectric layer 310 is SiO2, phosphoric acid if the dielectric layer 310 is Si3N4, or other suitable etching agents selected depending on the material of the dielectric layer 310. In act 435 the released micro-scale feedstock elements 325 are collected, for example, by filtering the etching agent 345 used to release them and optionally washed to neutralize the etching agent.
Various modifications may be made to the above process. For example, instead of a layer of dielectric 310 being deposited on the silicon wafer 305 and then removed by chemical etching, a layer of a polymer, for example, a photoresist, polyimide, or another polymer, may be deposited on the silicon wafer 305 and later removed by, for example, exposure to a solvent (ethylene glycol, gamma-butyrolactone, cyclopentanone, N-Methyl-2-pyrrolidone, or other known solvents) and/or by thermal decomposition as is known in the semiconductor fabrication arts to release the formed micro-scale feedstock elements. Alternatively, polyvinylalcohol (PVA), which is soluble in water, could be used as layer 310 and subsequently removed by exposure to water in act 435. The photoresist 320 may be positive photoresist that becomes soluble when exposed to radiation through the photomask and thus is exposed in areas other than those having the desired shapes for the micro-scale feedstock elements 325. In some embodiments, the layer 315 from which the feedstock elements 325 are formed may itself be a photoimagable polymer, for example, SU-8, in which instance the first photoresist layer 220 may not be necessary and the layer 315 may be directly patterned by exposure to patterning radiation and development in developer solution. In some embodiments, differently sized and/or shaped micro-scale feedstock elements may be formed concurrently on the same wafer while in other embodiments only micro-scale feedstock elements having same dimensions are formed on a single wafer.
In further embodiments, for example, instead of forming rod or bar shaped micro-scale feedstock elements 325, the feedstock elements 325 may be formed as block or cube shaped elements. For example, comparing
In some embodiments, block or cube shaped feedstock elements, or elements having different three dimensional shapes, for example, spheres or regular or irregular prisms other than blocks or cubes may be utilized as linker elements 1135, discussed below, that may be used as an intermediate element to join other feedstock elements (or a feedstock element to a substrate.) The linker elements 1135 may be formed with shapes, for example, with walls disposed at desired angles relative to one another that provide for feedstock elements joined with the linker elements 1135 to be joined at pre-determined desired angles. The linker elements 1135 may be formed with sides, or functionalized portions thereof, having sizes that allow for a predetermined number of feedstock elements, for example, between 1 and about 10 or more to bond to the sides of the linker elements 1135. The predetermined number of feedstock elements may be defined by a size of the bonding areas of the predetermined number of feedstock elements relative to the size of the sides, or functionalized portions thereof, of the linker elements 1135.
Another embodiment of a process 600 for forming micro-scale feedstock elements 325 is described with reference to
In act 610, a mold material, for example, wax, silicone, an epoxy-based material, or another mold material known in the art is deposited on the array of structures and allowed to cure to form a mold 520. (
In act 615, the cured mold 520 is removed from the semiconductor wafer 505 and array of structures 510. (
In act 620 a desired material 525, in a liquid or slurry form, is deposited in the impressions 530 in the mold 520 formed by the array of structures 510 and excess material 525, for example, from the surface 540 of the mold is removed. (
In act 625 a layer of adhesion material 340, for example, any one or more of the adhesion materials 340 discussed above is deposited on desired portions of the solidified material 525, for example, on end portions 545 exposed in the impressions 530 in the mold 520. (
In some embodiments where it is desired to deposit the one or more of the adhesion materials 340 on additional portions of the solidified material 525, the mold 520 may be cut to expose the additional portions, for example, other end portions 550 of the solidified material 525. (
In act 640, the solidified material 525 with the deposited adhesion material(s) 340 is removed from the mold 520, for example by melting of the mold material, dissolution of the material of the mold in a solvent, by cutting the solidified material 525 from the mold, or by other methods known in the art, resulting in a plurality of free micro-scale feedstock elements 325 which are then collected for later use.
In some embodiments disclosed herein, structures are formed including nanotubes as micro-scale feedstock elements. The nanotubes may be utilized for any of the feedstock elements disclosed herein. The nanotubes may comprise or consist of carbon, boron, or other elements. Carbon nanotubes may have diameters as small as a few nanometers. Carbon nanotubes may be formed by a CVD process in which the carbon nanotubes form on metal catalyst particles, for example, particles of nickel, cobalt, iron, or a combination thereof. The catalyst particles can stay at the tips of the growing nanotube during growth, or remain at the nanotube base during growth. The catalyst particles are often removed from carbon nanotubes available from various suppliers. However, in some embodiments the catalyst particles may be retained on the carbon nanotubes and used as the adhesion material 340 to which click chemicals and associated binder molecules may be adhered to facilitate attachment of the carbon nanotubes to other micro-scale feedstock elements. In other embodiments, defects, for example, carboxylic acid may be preferentially generated on end portions of carbon nanotubes to facilitate bonding to an adhesion material, for example, an amide group bonded to a substrate or to another feedstock element.
Nano-Scale Feedstock Fabricated with Methods Utilizing Block Copolymers
In some embodiments, it may be desirable to form feedstock elements for the fabrication of micro or macro-scale structures having dimensions smaller than those achievable with conventional lithographic processes, for example, rods, bars, cylinders, or prisms with widths or diameters of about 20 nm or less. It may be desirable to form such nanoscale feedstock elements from materials such as silicon, silicon dioxide, titanium dioxide, zinc oxide, tungsten, or other materials having desired physical, chemical, optical, electrical, or magnetic properties. In some embodiments, one may capitalize on the ability of various types of di-block or multi-block copolymers to self-assemble into nanoscale structures in methods to form such nanoscale feedstock elements.
In one specific example of block copolymer self assembly, a diblock copolymer composed of 70% polystyrene (PS) and 30% poly(methyl-methacrylate (PMMA) (poly(styrene-b-methyl methacrylate), referred to hereinafter as 70:30 PS-b-PMMA) with a total molecular weight of 64 kg/mol is deposited into a trench having a width of from about 100 nm to about 600 nm etched into the surface of a substrate, for example, silicon or silicon dioxide. The 70:30 PS-b-PMMA will spontaneously form hexagonal lattices of 20 nm diameter cylindrical PMMA domains in a matrix of PS. The PMMA may be removed from the cylindrical domains by immersion in acetic acid, leaving behind a pattern of 20 nm wide trenches from which nanoscale feedstock elements may be formed. An example of a nanoscale feedstock assembly method utilizing 70:30 PS-b-PMMA is illustrated in
In
Alternatively, starting at 7C, the PMMA cylinders can be converted to an inorganic material, for example, alumina, through sequential infiltration synthesis. The alumina rods can serve as an etch mask for the PS matrix to expose the layer into which nanorods are to be patterned 705C and as an etch mask for forming the nanorods 740 in the nanorod layer 705C. (See
The nanorods 740 may then be released from the remainder of the substrate 705 by removing any remaining photoresist using known photoresist stripping methods, and by dissolving or etching away layer 705B by exposure to a wet etching agent, for example, hydrofluoric acid if the layer 705B is SiO2, phosphoric acid if the layer 705B is Si3N4, or other suitable etching agents selected depending on the material of the layer 705B. If the underling substrate 705A is silicon and there is no intermediate layer, a dry XeF2 etch or a wet KOH or TMAH etch could release the nanorods 740. The released nanorods 740 may be collected, for example, by filtering the etching agent used to release them and optionally washed to neutralize the etching agent.
Various modifications may be made to the above process. For example, instead of layer 705B being silicon oxide or silicon nitride, layer 705B may be a layer of a polymer, for example, a photoresist, polyimide, or another polymer, that may be deposited on the layer 705A and later removed by, for example, exposure to a solvent (ethylene glycol, gamma-butyrolactone, cyclopentanone, N-Methyl-2-pyrrolidone, or other known solvents) and/or by thermal decomposition as is known in the semiconductor fabrication arts to release the formed nanorods 740. Alternatively, polyvinylalcohol (PVA), which is soluble in water, could be used as layer 705B and subsequently removed by exposure to water to release the formed nanorods 740. Further, the diameters of the PMMA domains and thus, the nanorods 740 formed in this process may be adjusted by adjusting factors such as the amount of PS v. PMMA in the PS-b-PMMA copolymer. A larger percentage of PMMA may result in larger diameter PMMA domains and a lesser percentage of PMMA may result in smaller diameter PMMA domains than in the example described above. In some embodiments, the diameter of the PMMA domains may vary from about 5 nm to about 50 nm.
The shape of the PMMA domains may be adjusted by adjusting the depth of the trench 710. As described above, a trench with a depth of about 25 nm would result in half cylinder domains of PMMA being formed using 70:30 PS-b-PMMA copolymer. Increasing the depth of the trench and/or decreasing the percentage of PMMA in the PS-b-PMMA copolymer may provide for full cylinders of PMMA domains fully embedded in a PS matrix to be formed.
Another method of forming nanoscale feedstock elements, for example, nanorods of materials including, but not limited to one or more of alumina, titania, zinc oxide, or tungsten utilizing block copolymers involves Sequential Infiltration Synthesis (SIS) of self assembled domains in a block copolymer. An example of this method is illustrated in
The film receiving regions 805 may extend entirely or substantially entirely across the width of a wafer 830 formed of the substrate 815 (
Nanoscale feedstock elements comprising, consisting, or consisting essentially of one of, for example, alumina, titania, zinc oxide, or tungsten may then be formed from the PMMA rods 820 of the annealed block copolymer by SIS. In the SIS process, the annealed block copolymer is first exposed to a vapor including a metal precursor, for example, one of TiCl4, AlCl3, Al(CH3)3, or another known metal precursor that diffuses through the PS matrix and reacts with carbonyl groups in the PMMA domains. Non-coordinated excess metal precursors may be removed from annealed block copolymer, for example, by a purge step with high purity N2. The first monolayer of metal precursors that are bound to the carbonyl groups of the PMMA provide reactive sites to which materials introduced in vapor form to the annealed block copolymer, for example, in an Atomic layer Deposition (ALD) process, bond. For example, to form Al2O3 nanorods, the annealed PS-b-PMMA copolymer is exposed to Al(CH3)3/H2O vapor in an ALD deposition apparatus. A coordination reaction occurs between the Al(CH3)3 and carbonyl groups in the PMMA, which is followed by H2O hydrolysis and results in the formation of a first monolayer of an Al—OH species in the PMMA domain. Subsequent ALD cycles of Al(CH3)3/H2O exposure (for example, with 300 s of N2 purge and 60 s of Al(CH3)3/H2O exposure per cycle) result in the formation and bonding of Al2O3 to the first monolayer of Al—OH species and building up of an Al2O3 cylinder layer by layer in the PMMA domain. A number of ALD cycles may be performed to grow the Al2O3 cylinder to a desired diameter. For example, after 10 ALD cycles, an Al2O3 cylinder having a diameter of about 30 nm will have been formed.
After the Al2O3 cylinders have been grown to a desired diameter, the Al2O3 cylinders may be functionalized with materials to which click chemical groups will bond or functionalized directly with desired click chemical groups. In one embodiment, end faces of the PS matrix including the formed Al2O3 cylinders may be etched, for example, utilizing an O2 plasma etch to expose ends of the Al2O3 cylinders. A desired material may be deposited on the ends of the Al2O3 cylinders by, for example sputtering or CVD. Different materials may be deposited on different ends of the Al2O3 cylinders so that different or complimentary click chemical groups may be bonded to the opposite ends of the Al2O3 cylinders.
The PS matrix is then removed to release the Al2O3 nanoscale feedstock elements, for example, by dissolution of the PS in an appropriate solvent. The released Al2O3 nanoscale feedstock elements are then collected, for example by filtering the solvent used to dissolve the PS.
A similar method is used to form TiO2 cylinder nanoscale feedstock elements from annealed PS-b-PMMA copolymer. To form the TiO2 cylinder nanoscale feedstock elements, the annealed PS-b-PMMA copolymer may be exposed to a TiCl4/H2O vapor in an ALD deposition apparatus. The TiCl4 coordinates to carbonyl groups in the PMMA domains of the annealed PS-b-PMMA copolymer and hydrolyze to form Ti—OH. The Ti—OH species serve as reactive sites for subsequent TiCl4/H2O ALD deposition cycles to build up the TiO2 cylinder nanoscale feedstock elements.
SiO2 cylinder nanoscale feedstock elements may be formed from annealed PS-b-PMMA copolymer by Al-catalyzed SiO2 ALD. The annealed PS-b-PMMA copolymer is first exposed to Al(CH3)3/H2O vapor in an ALD deposition apparatus. A coordination reaction occurs between the Al(CH3)3 and carbonyl groups in the PMMA, which is followed by H2O hydrolysis and results in the formation of Al—OH species in the PMMA domain. Subsequent ALD cycles using silanol vapor and N2 purges (for example, alternating silanol exposures for 400 s and N2 purges for 1,200 s) will result in the silanol reacting with the Al—OH species to form SiO2.
ZnO cylinder nanoscale feedstock elements may be formed from annealed PS-b-PMMA copolymer by Al-catalyzed ZnO ALD which involves first forming Al—OH species in the PMMA domains of the annealed PS-b-PMMA copolymer by Al(CH3)3/H2O ALD and subsequent diethyl zinc ALD cycles (for example, alternating diethyl zinc exposures for 300 s and N2 purges for 300 s). Tunsten cylinder nanoscale feedstock elements may be formed from annealed PS-b-PMMA copolymer by Al-catalyzed W ALD which involves first forming Al—OH species in the PMMA domains of the annealed PS-b-PMMA copolymer by Al(CH3)3/H2O ALD and subsequent alternating ALD exposures to Si2H6 and WF6 species.
It should be appreciated that various modifications may be made to the SIS process described above. PS-b-PMMA block copolymer is only one example of a block copolymer which self assembles into different polymer domains which may be utilized to form nanoscale feedstock elements. Various other known block copolymers that may be suitable for forming nanoscale feedstock elements via a SIS process may include, for example, poly(3-hexylthiophene)-b-perylene diimide acrylate, poly(3-hexylthiophene)-b-vinyl pyridine, poly(3-hexylthiophene)-b-lactide, polystyrene-b-polyethyleneoxide, poly(styrene-b-isoprene), poly(styrene-b-butadiene-b-methyl methacrylate), poly(styrene-b-(ethylene-co-butylene)-b-methylmethacrylate), poly(styrene-b-4-vinylpyridine), poly(isoprene-b-ethylene oxide), poly(styrene-b-ethylene oxide), poly(styrene-b-2-vinylpyridine), poly(styrene-b-hydroxystyrene), poly(styrene-b-n-butyl methacrylate), poly(styrene-b-ferrocenyldimethylsilane), poly(styrene-b-dimethylsioxane), poly[styrene-b-(ethylene-alt-propylene)], poly(styrene-b-ethylene butylene-b-styrene), and poly(styrene-b-butadiene). Some of these block copolymers may self-assemble into rectangular shaped bar-like domains 1000 (See
Instead of or in addition to reacting metal precursors to carbonyl groups in PMMA domains of a PS-b-PMMA block copolymer, other metal precursors may be utilized to bond with different polymer units in block copolymer domains of different block copolymers through, for example, metal-ligand coordination, covalent bonding, or other interactions. For example, the pyridine groups in polyvinylpyridine, a common block in many block copolymers, could selectively bind metal compounds including, for example, Al(CH3)3, AlCl3, ZnCl2, or CdCl2. The hydroxyl groups in polyacrylic acid, another common block in many block copolymers, could react with Al(CH3)3, TiCl4, or Zn(C2H5)2 to form covalent bonds. Any of these metal precursors may be utilized as precursors for the growth of various materials in a block domain of a block copolymer using, for example, an ALD process as described above.
In any of the methods of forming feedstock elements disclosed above, functionalized portions of the feedstock elements may include one or more long-chain molecules (for example, polyethylene glycol or a polymer or peptide chain) bonded to the feedstock elements between the bodies of the feedstock elements and the click chemical molecule or molecules or click chemical group or groups connected to the feedstock elements. The long-chain molecules may provide flexibility to the click chemical molecules and/or the ability of the different ends of the click chemical molecules to orient in different directions to provide for bonding of other elements to the feedstock elements in different orientations.
“Click chemistry” is a term for a type of chemical synthesis used for generating substances quickly and reliably by joining small units together. Click chemistry describes a way of generating products that follows examples in nature, which also generates substances by joining small modular units. The term was coined by K. Barry Sharpless in 1998, and was first fully described by Sharpless, Hartmuth Kolb, and M. G. Finn of The Scripps Research Institute in 2001.
In some embodiments, “click chemistry” reactions are used to join micro-scale or nano-scale feedstock elements to substrates and/or other micro-scale or nano-scale feedstock elements to form embodiments of structures disclosed herein. Feedstock faces or side portions to be joined (and/or feedstock faces and areas of a substrate to be joined) are patterned with complementary chemical groups, referred to herein as A-A′ pairs, B—B′ pairs, C—C′ pairs etc. (where A will bond to A′ but not B, B′, C, or C′, B will bond to B′ but not A, A′, C, or C′, etc.) that will bond them together with covalent, permanent click reactions. Such covalent bonds are stable to variations in solution conditions, temperature, and removal of water, making them a highly robust approach to hierarchical structure assembly.
Various different “click” reactions may be utilized in embodiments of assembly methods and structures disclosed herein. In one example, alkyne (or cyclooctyne) and azide functional groups represent one such A-A′ pair, displaying one of the most efficient, selective and versatile click reactions known, Huisgen 1,3-dipolar cycloaddition. In another example, the Michael addition of thiols to alkenes (i.e. maleimides) may be used as an alternate A-A′ pair. The reaction of aldehydes with alkoxyamines to form oximes provides a third A-A′ pair that is orthogonally reactive. The oxidative coupling of substituted phenols to anisidine derivatives may be used to provide a fourth A-A′ coupling. Biotin and streptavidin functional groups represent another such A-A′ pair. Multiple other A-A′ click chemical pairs are known in the art.
The high reactivity of the click-active functional moieties is incompatible with most traditional lithographic patterning schemes. To overcome this limitation, some embodiments involve conventional microfabrication techniques to bond an intermediate material to portions of a substrate or a micro-scale or nano-scale feedstock element that is used to bond a click chemical group and/or a linker molecule and click chemical group to the substrate or a micro-scale or nano-scale feedstock element. In some embodiments, a surface of a substrate is patterned with a material to which precursors that will bind to the click chemistries will selectively functionalize (e.g. gold surfaces to which thiols will bind, silicon surfaces to which silanes will bind, or iron oxides and other metals to which carboxyl groups will bind). If micro-scale or nano-scale feedstock elements are fabricated in a template or mold as discussed above (for example, as electroplated pillars in a mold or SIS formed feedstock elements in a polymer matrix) functionalization could occur on the exposed faces before removal from the mold.
After microfabrication of building blocks and functionalization with chemically distinct surfaces, the relevant “click” precursor groups are grafted to the surface of substrates and/or feedstock to produce surfaces with the desired functionality. The specificity of click reactions will potentially enable multiple reactions to be performed simultaneously, providing maximum versatility in the design of the final assembly process. In some embodiments, all “click” reactions may be performed under conditions where they are spontaneous, such that when two surfaces come into contact they react instantly to form a strong, permanent bond. In other embodiments, for example, if the fast rate of reaction leads to an unacceptable level of defects, the reactions may be performed under activated conditions, where the addition of a catalyst (Cu for azide-alkyne, a thiol reductant for thiol-maleimide, aniline for oxime chemistry, or the oxidant for phenol oxidative coupling) is used to trigger the covalent bond only once the particles have annealed into the correct configuration. In this case, weak non-covalent interactions such as hydrogen bonding donors/acceptors or electrostatic interactions can be used to promote appropriate orientation of feedstock on a substrate or other feedstock before covalent bond formation.
In some embodiments, a linker may be used to join the click chemical groups to metal patterns on a substrate and/or to feedstock elements. The linker may be considered a spacer between the surface functionalization (i.e. thiol) and the click chemistry. Examples of linkers include alkyls, aryls, or heteroatom substituted alkyl chains (which allow tunability of solubility, spacing, and/or mechanical stiffness.
In the field of medical diagnostics, DNA selective sensors have been developed that allow for one to detect the presence of one or more pathogens (for example, virus or bacteria) in a fluid sample by sensing the presence of strands of DNA specific to the one or more pathogens. Various DNA selective sensors include a sensor element, for example, a thin gold wire or other nanostructure to which a portion of a strand of DNA complimentary to the DNA of a pathogen of interest has been attached. When a strand of DNA of the pathogen having an order of base units (A, C, G, T) complimentary to the strand of DNA attached to the sensor element contacts the strand of DNA attached to the sensor element, the two strands of DNA bond together and produce a mechanical or electrical change on the sensor element that may be detected to provide an indication of the presence of the pathogen.
In some embodiments, the ability of complimentary strands of DNA to selectively bond to one another may be capitalized on to provide for a method of joining micro-scale or nano-scale feedstock elements as disclosed herein. For example, in some embodiments, a first strand of DNA is bonded to a substrate in locations where it is desired to attach first micro-scale feedstock elements. A strand of DNA complimentary to the first strand of DNA is bonded to an area of a first micro-scale or nano-scale feedstock elements desired to be bonded to the substrate. As illustrated in
In some embodiments, in addition to providing for bonding of the first micro-scale or nano-scale feedstock element L1 to the substrate 705 with the complimentary DNA strands, additional bonding mechanisms 725 are provided. For example, in addition to the complementary DNA strands, one or both of the substrate 705 and the first micro-scale or nano-scale feedstock element L1 are provided with an additional bonding mechanism 725 at the desired bonding locations. The additional bonding mechanisms 725 may include, for example, but without limitation, an adhesive that may be activated by heat (wax, hot-melt adhesive, etc.) or exposure to one or more forms of radiation (UV light, actinic radiation, etc.) and/or a solder material (for example, an indium/gold or lead/tin eutectic alloy). After the first micro-scale or nano-scale feedstock element L1 is bonded to the substrate 705 via the complimentary DNA strands, the additional bonding mechanisms may be activated by application of heat or radiation to form a bond between the first micro-scale feedstock element L1 and the substrate 705 that may be stronger than the bond between the complimentary DNA strands and that may be more robust in dry environments than the bond between the complimentary DNA strands.
Additional micro-scale or nano-scale feedstock elements may be functionalized with DNA strands complimentary to other DNA strands bonded to desired areas on the first micro-scale or nano-scale feedstock element L1 to provide for the additional micro-scale feedstock elements to be bonded to the first micro-scale or nano-scale feedstock element L1 in a similar manner as the first micro-scale or nano-scale feedstock element L1 is bonded to the substrate 705. This DNA assisted bonding process may be extended to join a plurality of levels of micro-scale or nano-scale feedstock elements into a desired structure.
Three Dimensional Lattice Structures Formed from Nano-Scale Feedstock
Micro and nano-scale feedstock elements may be joined with methods disclosed herein to form meta-materials including lattice structures that have properties, for example, strength to weight ratios, weight specific energy absorption, stiffness, strength to density ratios, and other physical or optical, electrical, or magnetic properties that are unobtainable with conventional engineering materials. In the specific example of a structural aerogel, a meta-material aerogel may be formed from 30 nm diameter×500 nm long SiO2 struts fabricated in accordance with methods disclosed herein and assembled into an octet truss structure using bonding methods disclosed herein. See
A structural aerogel may also exhibit greater insulative behavior (lesser thermal conductivity) that a conventional silica aerogel because the octet truss structure presents a higher thermal resistance than the random network of a conventional silica aerogel. The structural aerogel may this exhibit a unique combination of thermal insulation and mechanical strength as compared to conventional engineering materials (See
Other lattice structures formed from micro or nano-scale feedstock elements may provide for more than a ten times improvement in weight specific energy absorption and may promise greatly reduced transmitted impulse and contact stress as compared to conventional foams, elastomers, or honeycomb structures. These improvements in dynamic energy absorption of lattice structures formed from micro or nano-scale feedstock elements are due to tailorable lattice architecture (e.g., selection of materials, topology, and layering), greatly superior lattice strut lengths, and the ability to greatly reduce relative density, thereby delaying the onset of “densification” under stress. Lattice structures formed from micro or nano-scale feedstock elements may thus be desirable in implementations including, for example, personal protective equipment (sporting equipment such as helmets or military armor), vehicle crash protection (either in impact surfaces or in seats to act as velocity change buffers to reduce spinal injuries), air blast protection for personnel, vehicles, and structures, and underwater impulse/shock protection for personnel and equipment.
An example of a method of forming a three dimensional lattice from micro or nano-scale feedstock elements is illustrated in
In some embodiments, the substrate 1110 is conductive (for example, highly doped silicon) and/or is coated with a conductive thin film, for example, a metal, indium tin oxide, or another conductive material to facilitate the spread of charge across the surface of the substrate 1110 to aid in creating an electric field to align, orient, and/or move micro-scale feedstock elements into place on the surface of the substrate 1110.
The substrate is exposed to a fluid including a first set of feedstock elements 1110, for example, micro or nano-scale rods or bars having first ends 1115 functionalized with click chemical groups 1120 complimentary to the click chemical groups 1105 on the substrate 1100. For example, the first ends of 1115 of the first set of feedstock elements 1110 may be coated with SiO2 (or the first set of feedstock elements 1110 may be formed from SiO2) to which the silane side of a bifunctional click chemical molecule having an alkyne group on a second side of the molecule has been bonded. The bifunctional click chemical molecule (and/or click chemical molecules bonded to the substrate, linker elements, or any of the other feedstock elements disclosed herein) may also include an intermediate chemical group, for example, PEG, a polymer chain, or a peptide chain bonded between the first and second click chemical groups (e.g., the silane and alkyne click chemical groups). The micro or nano-scale rods or bars have second ends 1125 that are functionalized with either the same click chemical groups 1120 as the first ends 1115, the same click chemical groups 1105 as the substrate 1100, or different click chemical groups 1130. For example, the second ends 1125 of the micro or nano-scale rods or bars may be coated with gold to which the thiol side of a bifunctional click chemical molecule having a second side including an azide is bonded to. Alternatively, the second ends 1125 of the micro or nano-scale rods or bars may be coated with or be formed from SiO2 to which the silane side of a bifunctional click chemical molecule having a second side including an alkyne group is bonded to.
The first set of feedstock elements 1110 are aligned on the substrate 1100 using one of the directed fluid assembly methods disclosed above or are permitted to diffuse through the fluid until the click chemical groups 1120 on the first ends 1115 come into contact with the click chemical groups 1105 on the click chemical molecules bonded to the substrate 1100. For example, the free ends of the click chemical molecules may be subject to forces caused by Brownian motion of the fluid in which the substrate is immersed and may move until coming into contact with the click chemical groups 1120 on the first ends 1115 of the first set of feedstock elements 1110. The click chemical groups 1105 and 1120 bond to one another, bonding the first set of feedstock elements 1110 to the substrate 1100 in a defined pattern and orientation. In some embodiments, different bonding points on the substrate 1100 include different click chemical groups and different ones of the first set of feedstock elements 1110 may have different complimentary click chemical groups and may include different materials or have different sizes or shapes than others of the first set of feedstock elements 1110. Different ones of the first set of feedstock elements 1110 having different properties may bond to different predetermined spots on the substrate 1100.
Functionalized areas of the substrate 1100 may have areas greater than areas of the portions of feedstock elements 1110 (for example, areas of end portions of the feedstock elements) that bond to the functionalized areas of the substrate. Accordingly, multiple feedstock elements may bond to individual functionalized areas of the substrate.
The second ends 1125 of the first set of feedstock elements 1110 are then exposed to linker elements 1135, for example, by immersing the substrate 1100 including the bonded first set of feedstock elements 1110 in another fluid including the linker elements 1135. The linker elements 1135 include at least one portion or side functionalized with a click chemical group 1140 complimentary to the click chemical group 1130 on the second ends 1125 of the first set of feedstock elements 1110. The linker elements 1135 may be spheres or three dimensional prisms with a desired number of sides, for example, cubes. In some embodiments, the linker elements 1135 may include a click chemical group or groups connected to long-chain molecules (for example, polyethylene glycol, a polymer chain, or a peptide chain). Chemical groups on first ends of the long chain molecules may bond to bodies of the linker elements 1135 while click chemical groups bonded to another side or portion of the long chain molecules may include the click chemical group 1140 complimentary to the click chemical group 1130 on the second ends 1125 of the first set of feedstock elements 1110. The long-chain molecules may provide flexibility to the linker elements 1135 and/or the ability for click chemical groups on different sides or portions of the linker elements 1135 to orient in different directions. Different sides or portions of the linker elements 1135 (or associated long-chain molecules) may be functionalized with the same or different click chemical groups 1140, 1145, which, in some embodiments, may be the same click chemical groups 1105 that are bonded to the substrate 1100 or the first or second ends of the first set of feedstock elements 1110.
The linker elements 1135 maybe sized and/or shaped to set the coordination and/or relative angle between different feedstock elements, or groups thereof, that bond to the linker elements 1135. For example, for the linker elements 1135 illustrated in
In some embodiments, the strength of bonds between linker elements 1135 and feedstock elements may be controlled and bonds between certain feedstock element types and/or bonds to certain sides of the linker elements 1135 may have different strengths. For example, certain bonds may bend easily (for example, to simulate a pin joint between elements) and other bonds may be more rigid. The different bond strengths can be tuned by tuning the length or materials or other properties of long-chain molecules disposed between click chemical groups in click chemical molecules bonded to different sides of the linker elements 1135 and/or to different linker elements 1135 and/or to different feedstock elements. In some embodiments long-chain molecules may be disposed between click chemical groups in click chemical molecules bonded to only selected different sides of the linker elements 1135 and/or to different linker elements 1135 and/or to different feedstock elements.
The linker elements 1135 are brought into contact with the second ends 1125 of the first set of feedstock elements 1110 using one of the directed fluid assembly methods disclosed above or through diffusion or under the influence of Brownian motion of the molecules of the fluid in which the substrate is immersed, and the click chemical groups 1140 of the linker elements 1135 bond to the click chemical groups 1130 on the second ends 1125 of the first set of feedstock elements 1110, bonding the linker elements 1135 to the second ends 1125 of the first set of feedstock elements 1110. In some embodiments, different linker elements 1135 having different click chemical groups and/or different shapes or other properties may bond to different ones of the first set of feedstock elements 1110.
The free sides of the linker elements 1135 are then exposed to a second set of feedstock elements 1150, for example, by immersing the substrate 1100 including the bonded first set of feedstock elements 1110 and linker elements 1135 in another fluid including the second set of feedstock elements 1150. The second set of feedstock elements 1150 may be rods or bars made of the same or different material(s) than the first set of feedstock elements 1110. The second set of feedstock elements 1150 include first ends 1155 functionalized with a click chemical group 1160 and second ends 1165 functionalized with a click chemical group 1170. Click chemical groups 1160 and 1170 are, in some embodiments, the same chemical groups and may be the same or different from the click chemical groups 1120, 1130 bonded to the first and second ends of the first set of feedstock elements 1110. The click chemical groups 1160, 1170 of the first and second ends 1155, 1165 of the second set of feedstock elements 1150 are complimentary to the click chemical groups 1140, 1145 on free sides of the linker elements 1135. In some embodiments, the click chemical groups 1160, 1170 are bonded to the first and second ends 1155, 1165 of the second set of feedstock elements 1150 via one or more long chain molecules, for example, polyethylene glycol or a polymer chain or chains.
The first and second ends 1155, 1165 of the second set of feedstock elements 1150 are brought into contact with the linker elements 1135 using one of the directed fluid assembly methods disclosed above or through diffusion and the click chemical groups 1140, 1145 of the linker elements 1135 bond to the click chemical groups 1160, 1170 on the first and second ends 1155, 1165 of the second set of feedstock elements 1150, bonding the first and second ends 1155, 1165 of the second set of feedstock elements 1150 to the linker elements 1135 and by extension, to the first set of feedstock elements 1110. Different ones of the second set of feedstock elements 1150 may have different properties, for example, material(s) and/or shapes and/or sizes and may include different click chemical groups and may bond to different of the linker elements 1135 and different feedstock elements in the first set of feedstock elements 1110.
The second set of feedstock elements 1150 may be bonded to the first set of feedstock elements 1110 via the linker elements 1135 such that the longitudinal axes of the second set of feedstock elements 1150 are substantially perpendicular to the longitudinal axes of the first set of feedstock elements 1110. The first and second feedstock elements 1110, 1150 may be bonded together in a lattice structure. The first and second feedstock elements 1110, 1150 may be bonded together at different angles depending on the type of lattice or truss structure desired to be formed. The angle of bonding between the first and second feedstock elements 1110, 1150 may be determined by an angle of end faces of the first and second feedstock elements 1110, 1150 and/or the orientation of click chemical groups on ends of the first and/or second feedstock elements 1110, 1150 and/or by the shape of the linker elements 1135 and/or orientation of click chemical groups on the linker elements 1135. Bonding angles between different click chemical groups may also influence the orientation of the bond between the first and second feedstock elements 1110, 1150. Multiple feedstock elements of the second set of feedstock elements 1150 may be bonded in this manner to individual ends of individual ones of the first set of feedstock elements 1110. The bonded pattern of first and second feedstock elements 1110, 1150 may be considered a mesostructure pattern, a pattern that has characteristic dimensions, for example, dimensions of repeating patterns of bonded feedstock elements, in the meso-scale region between nano-scale and micro-scale dimensional regions.
At least one additional side of at least some of the linker elements 1135 are left free and include click chemical groups 1145 to which additional feedstock elements may be joined. The additional sides of the linker elements 1135 may serve the same function as the click chemical groups bonded to the substrate 1100, providing for additional layers of first and second feedstock elements and linker elements to be joined. Additional layers of first and second feedstock elements and linker elements may be subsequently be joined to build a lattice or truss structure having a desired size. For example, multiple layers of feedstock elements may be joined in accordance with the above disclosed method to form an octet truss as illustrated in
In some embodiments, mesostructured unit cells that would have linker elements, feedstock elements bonded between linker elements, and open click bonds could be assembled as described in the above paragraph then assembled onto a substrate in layers as described above, or assembled into a superstructure without a substrate.
It should be appreciated that in some embodiments, the linker elements 1135 may be omitted and the various feedstock elements may be joined directly to one another to form a lattice or truss structure. Different portions and/or sides of the feedstock elements may be functionalized with different click chemical groups to control the orientation of bonded feedstock elements. Multiple feedstock elements of one set of feedstock elements may bond to individual functionalized portions of individual feedstock elements of a second set of feedstock elements.
The substrate 1100 may not be necessary in all embodiments. In some embodiments, different feedstock elements may be introduced concurrently with one another in solution and may bond together via complimentary click chemical groups (and/or complimentary DNA strands) to form a lattice or truss structure without the feedstock elements needing to be supported on a substrate. A second set of feedstock elements may bond to both first and second ends of a first set of feedstock elements in solution (or to linker elements on the first and second ends of a first set of feedstock elements) to form at least a portion of a three dimensional lattice or truss structure. Additional feedstock elements may bond to other portions of the linker elements of the first or second feedstock elements to build the lattice or truss structure. This process may be repeated until the lattice or truss structure achieves a desired size.
Further, it should be appreciated that bonding sites including click chemical groups may be present not only on end portions of feedstock elements used to form a lattice or truss structure, but may also be present on intermediate portions or sides of the feedstock elements so that feedstock elements may bond to one another not only at their first and second portions on their ends but also at third portions displaced from their ends.
In another aspect, micro or nano-sized prisms may be utilized to form three dimensional structures with useful properties, for example, electronic structures. In one specific example, rectangular prisms, blocks, or cube-shaped feedstock elements fabricated in accordance with methods disclosed herein may be utilized to form an inductor. The inductor is formed from two different types of feedstock elements—feedstock elements comprising or consisting of an insulator, for example SiO2, and feedstock elements comprising or consisting of a conductive material, for example, copper or aluminum. The feedstock elements may be approximate 1 μm in height, length, and width, although smaller dimensions may be used and the feedstock elements need not necessarily have equal height, length, and width dimensions. The feedstock elements are functionalized with different click chemical groups on different faces to control what other feedstock elements they bond to. As illustrated in
The feedstock elements include insulative feedstock elements 1155 and conductive feedstock elements 1160. In one embodiment, the feedstock elements may be introduced into a fluid medium and moved into contact with one another by one of the directed fluid assembly methods disclosed above or are permitted to diffuse through the fluid until the complimentary click chemical groups on faces of the different feedstock elements contact one another and bond the feedstock elements together. Additional layers of feedstock elements may be added to build up the inductor layer by layer as illustrated in
Many different types of lattice or truss structures may be formed from micro or nano-scale feedstock elements as disclosed herein. The types of the lattice or truss structures may be determined based on factors including, for example, the shape and size of the different micro or nano-scale feedstock elements that may be utilized, the orientation of click chemical groups on the micro or nano-scale feedstock elements, the shape and size of the linker elements, and the orientation of different click chemical groups on the linker elements.
One type of lattice that may be formed from micro or nano-scale feedstock elements as described herein is an octet truss structure. An octet truss has a unit cell A as illustrated in
Another type of lattice that may be formed from micro or nano-scale feedstock elements as described herein include auxetic material lattices. Auxetic materials are materials that have a negative Poisson ratio and that expand in a widthwise direction when pulled on and strained in a lengthwise direction as illustrated in
Auxetic material lattices that may be formed from micro or nano-scale feedstock elements as described herein may include chiral material lattices. Chiral units in chiral structures include ligaments that are attached to nodes with rotational symmetry. The structures may be left handed or right handed. If the nodes are on opposite sides of the ligaments, the structure is considered chiral. If the nodes are on the same sides of the ligaments the structures is considered anti-chiral (racemic). “Meta-chiral” structures are those which include ligaments attached to nodes but with degrees of rotational symmetry that are different from the number of ligaments attached to each node. An example of a trichiral structure is illustrated in
Auxetic material lattices that may be formed from micro or nano-scale feedstock elements as described herein may include rotating units. Micro or nano-scale units may be joined with rotating bonds such that the units rotate with applied strain as illustrated in
Further auxetic structures that may be formed from micro or nano-scale feedstock elements as described herein may include nodules joined by fibrils. As illustrated in
Having thus described several aspects of at least one embodiment of this invention, it is to be appreciated various alterations, modifications, and improvements will readily occur to those skilled in the art. Such alterations, modifications, and improvements are intended to be part of this disclosure, and are intended to be within the spirit and scope of the invention. Accordingly, the foregoing description and drawings are by way of example only.
This application claims priority under 35 U.S.C. § 119(e) to U.S. Provisional Application Ser. No. 62/172,315 titled “METHOD OF ASSEMBLING NANOSCALE AND MICROSCALE OBJECTS,” filed Jun. 8, 2015, which is incorporated herein by reference in its entirety for all purposes.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US16/36456 | 6/8/2016 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 62172315 | Jun 2015 | US |
