The present disclosure relates to silicon membranes with nano to microscale pores/slits. More particularly, the present disclosure relates to methods of preparing and methods of using silicon membranes with nano to microscale pores/slits.
There is a need for precision filtration membranes bearing functionalization (i.e., surface coatings) in order to improve their utility in an application-specific manner. Such filtration membranes should offer high permeability and well-defined solute permeation characteristics (i.e., a large capacity to permeate specifically sized solutes, while retaining other specifically sized solutes). The functionalization of such membranes should not therefore reduce such solute permeability or selectivity. Further, the functionalization should promote the intended application; e.g., prevent fouling, promote selective solute permeation or retention, etc.
Silicon nanomembranes are one class of such high capacity and selective permeability filtration membranes. However, there is yet no practical, scalable, and industrially manufacturable means for stable (i.e., non-hydrolyzable) functionalization of silicon nanomembranes. Further, no such present functionalization method fulfills the application-specific utility needs nor the need to maintain permeability characteristics. For example, functionalization using only silane chemistries (e.g., to form Si—O—Si bonds) is prone to hydrolysis and removal from the surface due to incomplete surface functionalization. Adventurous molecules are able to approach within van der Waals interaction radii of silanes at low surface density (i.e., incomplete surface functionalization), and thus promote their hydrolysis. Such adventurous molecules may be solution components (H+, −OH, or other acids and bases) or other proximal silane molecules. For instance, Meller and Wanunu describe in U.S. Pat. No. 9,121,843 silane-based modifications of porous silicon nitride membranes. However, such silanes lack the requisite hydrolytic stability as is known to those skilled in the art. Therefore, there is a need to improve the density of surface functionalization.
Other possible means for modifying silicon nanomembranes have been described. For example, carbene precursors have been used to modify silicon nitride. However, the light-sensitive nature of carbenes and practical difficulties in obtaining highly purified carbenes makes this process unsuitable for industrial-scale manufacturing. As another example, alkylation-based methods for functionalizing bulk silicon nitride layers have been described. However, the harsh processing conditions associated with such methods makes them unsuitable for freely suspended silicon nanomembranes. As another example, grafted polymer brushes of zwitterionic materials (e.g., sulfobetaine methylacrylate) offer non-fouling surface grafts. However, the harsh free radical processing conditions and the resultant excess thickness of such polymer brushes makes them unsuitable for processing freely suspended silicon nanomembranes and for maintaining the permeability of such membranes.
There is an ongoing and unmet need for methods to better modify silicon nanomembranes.
In particular, the present disclosure describes methods for combinations of one or more surface modification processes that may yield highly dense surface monolayers that are not prone to hydrolysis nor significantly reduce membrane permeability. Such combination processes rely on multiple, distinct, and inherent reactive surface groups within silicon membranes, such that distinct chemical processes may be carried out using these one or more distinct surface reactive groups in order to functionalize membranes to a greater extent. Thus, multiple means for modifying silicon membranes may be possible with the methods of the present disclosure, which form the necessary dense surface monolayers that are required for hydrolytic stability. Further, one class of chemical process and functionalization, that yield more hydrolytically stable derivatives, may be used in combination with another class of chemical process and functionalization, that may suffer from hydrolysis, in order to promote the hydrolytic stability of the second class. Such a combination yields an overall higher surface density of functionalized groups, thus reducing attack by adventurous molecules that may displace them.
The present disclosure describes methods and uses of functionalized silicon membranes. In various examples, the methods disclosed herein describe membrane (e.g., nanomembrane) functionalization which may be used to functionalize silicon membranes (e.g., nanomembranes) with industrially scalable processes. In particular, the present disclosure describes methods for combinations of one or more surface modification processes that can yield highly dense surface monolayers that are not prone to hydrolysis nor significantly reduce membrane (e.g., nanomembrane) permeability.
In an aspect, the present disclosure provides functionalized silicon membranes. The functionalized silicon membranes (e.g., nanomembrane) are stable (i.e., non-hydrolyzable). In various examples, a functionalized silicon membrane (e.g., nanomembrane) is made by a method of the present disclosure.
In an aspect, the present disclosure provides methods of functionalizing a silicon membrane (e.g., nanomembrane). The methods are based on reaction of a reactive surface group on a surface of silicon nanomembrane (i.e., a substrate surface group) with a functional group on a functionalizing group precursor compound. In various examples, the methods can improve the hydrolytic stability of present (e.g., silane-based), as well as other, functionalization methodologies.
In an aspect, the present disclosure describes fluidic devices incorporating at least one functionalized silicon membrane (e.g., nanomembrane) and uses of such fluidic devices. For example, a fluidic device is used for filtration applications or methods.
For a fuller understanding of the nature and objects of the disclosure, reference should be made to the following detailed description taken in conjunction with the accompanying figures.
Although the disclosed subject matter will be described in terms of certain embodiments, other embodiments, including embodiments that do not provide all of the benefits and features set forth herein, are also within the scope of this disclosure. Various structural, logical, and process step changes may be made without departing from the scope of the disclosure.
Ranges of values are disclosed herein. The ranges set out a lower limit value and an upper limit value. Unless otherwise stated, the ranges include all values to the magnitude of the smallest value (either lower limit value or upper limit value) and ranges between the values of the stated range.
The present disclosure describes methods for functionalization of silicon membranes. The present disclosure further describes functionalized silicon membranes and uses thereof.
As used herein, unless otherwise stated, the term “group” refers to a chemical entity that has one terminus or two or more termini that can be covalently bonded to other chemical species. Examples of groups include, but are not limited to:
The term “group” includes radicals.
As used herein, unless otherwise indicated, the term “aliphatic” refers to branched or unbranched hydrocarbon groups that, optionally, contain one or more degrees of unsaturation. Degrees of unsaturation include, but are not limited to, alkenyl groups/moieties, alkynyl groups/moieties, and cyclic aliphatic groups/moieties. For example, the aliphatic group can be a C1 to C18 aliphatic group, including all integer numbers of carbons and ranges of numbers of carbons therebetween. The aliphatic group can be unsubstituted or substituted with one or more substituent. Examples of substituents include, but are not limited to, various substituents such as, for example, halogens (—F, —Cl, —Br, and —I), additional aliphatic groups (e.g., alkenes, alkynes), aryl groups, alkoxides, carboxylates, carboxylic acids, ether groups, silane groups, amine groups, thiol/sulfhydryl groups, isothiocyanate groups, epoxide groups, maleimide groups, succinimidyl groups, anhydride groups, mercaptan groups, hydrazine groups, N-glycan groups, O-glycan groups, and the like, and combinations thereof.
As used herein, unless otherwise indicated, the term “alkyl” refers to branched or unbranched saturated hydrocarbon groups. Examples of alkyl groups include, but are not limited to, methyl groups, ethyl groups, propyl groups, butyl groups, isopropyl groups, tert-butyl groups, and the like. For example, the alkyl group can be a C1 to C18 alkyl group, including all integer numbers of carbons and ranges of numbers of carbons therebetween,. The alkyl group can be unsubstituted or substituted with one or more substituent. Examples of substituents include, but are not limited to, various substituents such as, for example, halogens (—F, —Cl, —Br, and —I), aliphatic groups (e.g., alkyl groups, alkenyl groups, alkynyl groups), aryl groups, alkoxide groups, carboxylate groups, carboxylic acids, ether groups, silane groups, amine groups, thiol/sulfhydryl groups, isothiocyanate groups, epoxide groups, maleimide groups, succinimidyl groups, anhydride groups, mercaptan groups, hydrazine groups, N-glycan groups, O-glycan groups, and the like, and combinations thereof.
In particular, the present disclosure describes methods for combinations of one or more surface modification processes that may yield highly dense surface monolayers that are not prone to hydrolysis nor significantly reduce membrane permeability. Such combination processes rely on multiple, distinct, and inherent reactive surface groups within silicon membranes, such that distinct chemical processes may be carried out using these one or more distinct surface reactive groups in order to functionalize membranes to a greater extent. Thus, multiple means for modifying silicon membranes may be possible with the methods of the present disclosure, which form the necessary dense surface monolayers that are required for hydrolytic stability. Further, one class of chemical process and functionalization, that yield more hydrolytically stable derivatives, may be used in combination with another class of chemical process and functionalization, that may suffer from hydrolysis, in order to promote the hydrolytic stability of the second class. Such a combination yields an overall higher surface density of functionalized groups, thus reducing attack by adventurous molecules that may displace them.
The present disclosure describes methods and uses of functionalized silicon membranes. In various examples, the methods disclosed herein describe membrane (e.g., nanomembrane) functionalization, which may be used to functionalize silicon membranes (e.g., nanomembranes) with industrially scalable processes. In particular, the present disclosure describes methods for combinations of one or more surface modification processes that can yield highly dense surface monolayers that are not prone to hydrolysis nor significantly reduce membrane (e.g., nanomembrane) permeability.
In an aspect, the present disclosure provides functionalized silicon membranes. The functionalized silicon membranes (e.g., nanomembrane) are stable (i.e., non-hydrolyzable). In various examples, a functionalized silicon membrane (e.g., nanomembrane) is made by a method of the present disclosure. A silicon membrane may be referred to as a nanomembrane and may comprise a plurality of nanopores, micropores, or microslits, where a plurality of nanopores, micropores, or microslits may fluidically connect one or more membrane surface to an opposing one or more membrane surface and, optionally, at least one aperture.
Description of silicon membranes (e.g., nanomembranes) may also refer to description of functionalized silicon membranes (e.g., nanomembranes) and the term silicon membrane may be used when referring to functionalized silicon membrane (e.g., nanomembrane), including singular and plural forms.
A functionalized silicon membrane (e.g., nanomembrane) has a plurality of functionalizing groups disposed on at least a portion of a surface of a silicon membrane (e.g., nanomembrane). The groups comprise one or more terminal functional groups. The functionalized silicon membranes (e.g., nanomembranes) with one or more terminal functional groups exhibit one or more desirable properties. Without intending to be bound by any particular theory, it is considered that the terminal functional groups provide one or more desirable properties of a functionalized silicon membrane (e.g., nanomembrane).
The terminal functionalizing groups can be covalently bonded directly to a surface of a functionalized silicon membrane (e.g., nanomembrane) or covalently bonded to a surface of a functionalized silicon membrane (e.g., nanomembrane) via one or more linking groups. For the purposes of this disclosure, the terms terminal group, terminal group forming compound, and terminal moiety (in both singular and plural forms) are used synonymously. Terminal groups are not passively coated (e.g., physisorbed and/or chemisorbed) on the silicon membrane (e.g., nanomembrane).
The functionalization (e.g., individual functionalizing groups) is of appropriate atomic length and molecular size such that it does not significantly reduce the permeability of silicon membranes (e.g., nanomembranes). For example, a nanoporous silicon nitride membrane comprises a mean pore diameter of 50 nm. Functionalization of such a membrane (e.g., nanomembrane) with, for example, a three-carbon, five-carbon, or twenty-carbon alkane reduces mean pore diameter by 0.92 nm, 1.5 nm, and 6.2 nm, respectively. In the former two examples, the reduction in mean pore size will not significantly reduce permeability. However, the latter example will significantly reduce permeability (due to a greater than 10% reduction in mean pore diameter). In various examples, the functionalization does not reduce the mean of the longest pore dimension parallel to the longest axis of the pore (e.g., mean pore diameter) of at least a portion of the silicon membrane (e.g., nanomembrane) pores by greater than 10%, greater than 15%, or greater than 20%. Thus, it is desirable that the functionalization of silicon membranes (e.g., nanomembranes) be of limited atomic length and molecular size in order to prevent a decrease in membrane (e.g., nanomembrane) permeability. For the purposes of this disclosure, a significant reduction in permeability should be considered one that reduces mean pore size by more than 20%.
For purposes of this disclosure, surface density should be considered the number of, for example, surface reactive groups or resultant surface groups on silicon membranes (e.g., nanomembranes) that are covalently bonded to a silicon membrane (e.g., nanomembrane) surface, and thus, should be considered the extent of silicon membrane (e.g., nanomembrane) covered by such groups (i.e., surface coverage extent). The multiple, distinct reactive surface groups may be functionalized using one or more individual chemical processes that form covalently bonded linker and/or terminal groups on silicon membranes (e.g., nanomembranes). Surface density should be empirically determined buy one of the several metrology methods disclosed herein.
In an example, the surface coverage extent of functionalized surface density of reactive hydroxyl surface groups is 100% (i.e., such groups comprise complete reaction with either the epoxide or the silane functionalization methods described herein). As another example, the surface coverage extent of functionalized surface density of reactive amine surface groups is 100% (i.e., such groups comprise complete reaction with the aldehyde functionalization methods described herein). As another example, the surface coverage extent of functionalized surface density of reactive hydroxyl surface groups is 100% and the surface coverage extent of functionalized surface density of reactive amine surface groups is 100% (i.e., the hydroxyl groups comprise complete reaction with the silane functionalization methods described herein and the amine groups comprises complete reaction with the aldehyde functionalization methods described herein). Without intending to be bound by any particular theory, the extent of chemical activation of surface reactive groups, time, temperature, and concentration of epoxide, silane, and aldehyde reactants may all affect the extent of functionalization surface density. In various examples, the surface coverage extent of functionalized surface density of reactive surface groups (e.g., hydroxyl surface groups, amine groups, silane groups, and the like) is 95, 96, 97, 98, 99, 99.5, 99.9%. In various examples, the surface coverage extent of functionalized surface density is 20% to 100%, including all 0.1% values and ranges therebetween. In another example, the surface coverage extent of functionalized surface density is 40% to 80%, including all 0.1% values and ranges therebetween, where such a range provides a useful surface coverage extent. By “useful surface coverage extent,” it is meant that the range of surface coverage forms a biomolecule, non-fouling, and/or surface property modifying functionalized membrane for the uses disclosed herein. Examples of such uses may include, but are not limited to, hemodialysis, routine separations, or sterile filtration.
The functionalization is stable in hydrolytic environments. For example, high (e.g., ≥8) or low (e.g., ≤6) pH, high salt (e.g., ≥500 mM total salt), elevated temperature (e.g., ≥37° C.), and/or prolonged exposure duration may all promote hydrolysis of functional groups used to derivatize silicon membranes (e.g., nanomembranes). In examples disclosed herein, amine bonds (i.e., C—N bonds) are preferred due to their increased hydrolytic stability over silane bonds (i.e., Si—O—Si bonds). In further examples disclosed herein, amide-based derivatization of silicon membranes (e.g., nanomembranes) is combined with silane-based derivatization of silicon membranes (e.g., nanomembranes), such that the combination increases the density and surface coverage, and thus, promotes the hydrolytic stability of both functional derivatives. In an example disclosed herein, the functionalized silicon membranes (e.g., nanomembranes) are used for hemodialysis and the required hydrolytic stability is from several hours (e.g., ≥3 hours) to multiple days (e.g., ≥2 days). In another example disclosed herein, the functionalized silicon membranes (e.g., nanomembranes) are used for routine separations and the required hydrolytic stability is from several hours (e.g., ≥2 hours) to multiple days (e.g., ≥1 day). In another example disclosed herein, the functionalized silicon membranes (e.g., nanomembranes) are used for sterile filtration and the required hydrolytic stability is from several hours (e.g., ≥2 hours) to multiple days (e.g., ≥1 day).
For purposes of this disclosure, hydrolytic stability, hydrolytically stable, and non-hydrolyzable should be considered synonymous terms. Such terms refer to the extent of surface modification coverage that resists hydrolysis for the exemplary time-courses described herein. By “resistance” and “stability,” it is meant that the extent of surface coverage is unchanged (i.e., no detectable loss of covalently bonded groups) when comparing modified membranes (e.g., nanomembranes) exposed to hydrolytic conditions versus similarly modified membranes (e.g., nanomembranes) not exposed to hydrolyzing conditions, wherein the comparison to determine changes in extent of surface coverage is performed by one or more of the metrology techniques disclosed herein.
The silicon membranes (e.g., nanomembranes) may be nanoporous, microporous, or microslit membranes. For porous or slit membranes (e.g., nanomembranes), it is desirable that the addition of surface functionalization be of appropriate atomic length so as to not significantly reduce pore or width sizes, porosity, and/or permeability. Further, it is desirable that such surface functionalization exhibits practically no rate of hydrolysis (i.e., comprises covalently stable bonds) within a wide range of chemical and solution environments. In an example, the surface functionalization exhibits no observable rate of hydrolysis (i.e., comprises covalently stable bonds). The rate of hydrolysis can be determined by methods known in the art. For example, the rate of hydrolysis is determined by a metrology method disclosed herein.
In an example, the silicon membrane (e.g., nanomembrane) is a nanoporous silicon nitride membrane (NPN). Examples of NPN membranes and the fabrication of such membranes are disclosed in U.S. Pat. No. 9,789,239 (Striemer et al. “Nanoporous Silicon Nitride Membranes, and Methods for Making and Using Such Membranes”), the disclosure of which with regard to NPN membranes is incorporated herein by reference.
In another example, the silicon membrane (e.g., nanomembrane) is a microporous silicon nitride membrane (MP SiN). Examples of MP SiN membranes and the fabrication of such membranes are known in the related art.
In yet another example, the silicon membrane (e.g., nanomembrane) is a microslit silicon nitride membrane (MS SiN). Examples of MS SiN membranes and the fabrication of such membranes are disclosed in U.S. Application No. 62/546,299 (Roussie et al. “Devices, Methods, and Kits for Isolation and Detection of Analytes Using Microslit Filters”), the disclosure of which with regard to NPN membranes is incorporated herein by reference.
In yet another example, the silicon membrane (e.g., nanomembrane) is a microporous flat tensile silicon oxide membrane (MP SiO2). Examples of MP SiO2 membranes and the fabrication of such membranes are disclosed in U.S. Pat. No. 9,945,030 (Striemer et al. “Free-Standing Silicon Oxide Membranes, and Methods of Making and Using Same”), the disclosure of which with regard to MP SiO2 membranes is incorporated herein by reference.
Silicon membranes (e.g., nanomembranes) can be chips or dies. In various examples, the silicon membrane (e.g., nanomembrane) structure is a chip or die, where the chip or die is derived from a portion of or the entirety of a silicon wafer substrate. The structures can be monolithic structures, where the chip or die comprises at least one functionalized silicon membrane disposed on a portion or all of the silicon wafer substrate. The membrane comprises a plurality of surfaces (e.g., a first membrane surface, second membrane surface, etc.), one or more aperture, and a plurality of nanopores, micropores, or microslits within the silicon membrane (e.g., nanomembrane). For purposes of this disclosure, the terms substrate, chip, or die refer to silicon membranes (e.g., nanomembranes). One or more of these structures, chips, or dies may be incorporated into fluidic devices of the present disclosure.
In the various examples, the silicon membranes (e.g., nanomembranes) have a nanopore, a micropore, or a microslit density of 102 to 1010 pores/mm2, including all integer pores/mm2 values and ranges therebetween. In the various examples, the silicon membranes (e.g., nanomembranes) have a nanopore or a micropore diameter, or a microslit width of 11 nm to 10 μm, including all integer nm values and ranges therebetween. For NPN membranes, the mean nanopore diameter is, for example, at least 11 nm. The nanopore or a micropore diameter, or the microslit width, is not ≤10 nm. The porous or slit layer is disposed on a silicon wafer substrate of <100> or <110> crystal orientation. Further, one or more aperture extends through the thickness of the silicon wafer, such that a plurality of membrane surfaces are formed (e.g., a first membrane surface and a second (i.e., opposing) membrane surface) by the one or more aperture, and the plurality of nanopores, micropores, or microslits, are fluidically connected to the one or more aperture. The aperture surface comprises internal sidewalls within the substrate. The plurality of nanopores, micropores, microslits, and apertures all contribute to the surface area of the membrane chip or die. The aperture of the substrate can be formed by standard photolithographic patterning, reactive ion etching of a masking layer, wet chemical through-substrate etching, and other methods known to those skilled in the art. Through-substrate etching forms apertures connected with each first and each second membrane surface (i.e., formed by the one or more aperture) and the plurality of nanopores, micropores, or microslits, are fluidically connected to the one or more aperture.
In various examples, an aperture extends through the thickness of the silicon substrate such that a first membrane surface is formed by the aperture, and at least some of the plurality of nanopores, micropores, or microslits are fluidically connected to the aperture at the first membrane surface. In additional examples, one or more additional apertures extend through the thickness of the silicon substrate such that a corresponding one or more additional membrane surfaces are formed by the one or more aperture.
The silicon membranes (e.g., nanomembranes) can have a range of membrane thickness. In various examples, the nanoporous, microporous, or microslit membrane (e.g., nanomembrane) have a thickness of 20 nm to 10 μm, including all integer nm values and ranges therebetween.
In an example, an aperture has a longest dimension (e.g., a diameter) greater than or equal to 50 μm. In another example, an aperture has a longest dimension (e.g., diameter) of greater than or equal to 100 μm. In various examples, apertures can have dimensions of 100 μm by 100 μm, of 1 mm by 1 mm, of 1 mm by 10's of mm, or the like.
The functionalization can comprise various functionalizing groups. In an example, all of the functionalizing groups are the same. In another example, a functionalized silicon membrane (e.g., nanomembrane) comprises a combination of at least two different functionalizing groups. In various examples, the functionalized silicon membrane (e.g., nanomembrane) comprises two or more selectively functionalized membrane surfaces, one or more selectively functionalized aperture, one or more selectively functionalized intra-pore or intra-slit surface, and/or a combination thereof.
The functionalization may be non-fouling groups and/or surface property modifying groups. Examples of functionalizing groups are described herein. Such groups may be referred to as terminal forming compounds.
In an aspect, the present disclosure provides methods of functionalizing a silicon membrane (e.g., nanomembrane). The methods are based on reaction of a reactive surface group on a surface of silicon nanomembrane (i.e., a substrate surface group) with a functional group on a functionalizing group precursor compound. In various examples, the methods can improve the hydrolytic stability of present (e.g., silane-based), as well as other, functionalization methodologies.
In various examples, the disclosure describes covalent reaction chemistries for the modification of silicon membranes (e.g., nanomembranes). The functionalization may be non-fouling groups and/or surface property modifying groups. The functionalization may also be referred to as modification or as derivatization.
In an example, the methods disclosed herein for functionalizing silicon membranes (e.g., nanomembranes) comprise one or more selective chemistries which react with unique classes of functional groups of the silicon membranes (e.g., nanomembranes) (e.g., substrate surface groups). Thus, one selective chemistry may be used to functionalize a first substrate surface group, while a second selective chemistry may be used to functionalize a second substrate functional group, and the one or more selective chemistries may comprise distinct bonds linking to the silicon membrane (e.g., nanomembrane) substrate. For example, epoxidation or silanization is used to react with substrate surface hydroxyl groups to form Si—O—C or Si—O—Si bonds, respectively. As another example, aldehylation followed by reductive amination, is used to react with substrate surface amine groups to form Si—N—C bonds. In such examples, the first instance of “Si” refers to the Si of the silicon membrane (e.g., nanomembrane), the second instance of “O” or “N” refers to the atom derived from the substrate surface group, and the final instance of “C” or “Si” refers to the atom of the derivatizing molecule.
In various examples, functionalization methods disclosed herein are combined such that a greater extent of surface coverage and surface functionalization is achieved in comparison to use of only one functionalization method. Further, the combined functionalization may rely on amide bonds (which are less prone to hydrolysis) to protect silane bonds (which are more prone to hydrolysis). Thus, the amide bonds may provide a means for greater surface functionalization that can overcome the well-known problem of incomplete surface coverage of silanes (which promotes their hydrolysis and removal from the substrate surface).
In various examples, a method for the functionalization of silicon membranes (e.g., nanomembranes) using covalent reaction chemistries comprises activation or treatment of the membrane surface by solution-phase chemistries, such that reactive surface groups are formed (e.g., substrate surface hydroxyl or amine groups). Such substrate surface groups may be further reacted with a first molecule comprising at least one first reactive group that selectively reacts with substrate surface groups. Examples of such first molecules include, but are not limited to, epihalohydrins, aldehydes, and/or silanes, and the like. The first molecules may further comprise at least one second reactive group for further derivatization with one or more second molecules. These second molecules may include terminal groups (e.g., a non-fouling group, a surface modifying group, or combinations thereof). Alternatively, the first molecules may be cross-linked or covalently reacted to one another, and thus comprise at least two or more reactive groups for such cross-linking. Alternatively, the first molecules may comprise a first reactive group that reacts with substrate surface groups and one or more terminal groups as disclosed herein (i.e., intrinsic terminal groups). Alternatively, the second molecules may comprise a spacer of varying length (e.g., C1-C18 aliphatic groups, such as, but not limited to, alkyl groups), a first reactive group that reacts with the first molecule's reactive group, and at least one or more second reactive group that can react with any terminal group and/or can cross-link to any other second molecules.
Means for bonding first molecules (e.g., first compound) to terminal groups, first molecules (e.g., first compounds) to second molecules (e.g., second compounds), second molecules (e.g., second compounds) to terminal groups, cross-linking first molecules (e.g., first compounds) to first molecules (e.g., first compounds), and/or cross-linking second molecules (e.g., second compounds) to second molecules (e.g., second compounds) include substitution reactions (e.g., nucleophilic attack where a group (e.g., a halogen or other suitable leaving group) is displaced), click reactions (i.e., a 3+2 reaction between an azide moiety and alkynyl moiety), other reactions between a nucleophile (e.g., an amine, a thiol, an alkoxide, and the like) and electrophile (e.g., a maleimide, anhydride, epoxide, and the like), cross-coupling reactions (e.g., a Heck reaction and the like), and other strategies known in the art. For example, spacer groups are present between first molecules (e.g., first compounds) and terminal groups. In such an example, the spacer group (e.g., spacer compound) is covalently bonded to the first molecule (e.g., first compound) using methods described herein or known in the art, and the terminal group is covalently bonded to the spacer molecule (e.g., spacer compound) also using methods described herein or known in the art. Non-limiting examples of functional groups and or reaction partners include silane, amino, carboxyl, thiol/sulfhydryl, isothiocyanate, epoxide, iodo-, alkane, maleimide, succinimidyl, anhydride, mercaptan, hydrazine, N-glycan, or O-glycan, and the like. In an example, these groups are used for bonding first molecules (e.g., first compounds) to terminal groups, first molecules (e.g., first compounds) to spacer molecules (e.g., spacer compounds), spacer molecules (e.g., spacer compounds) to terminal groups, cross-linking first molecules (e.g., first compounds) to first molecules (e.g., first compounds), and/or cross-linking spacer molecules (e.g., spacer compounds) to spacer molecules (e.g., spacer compounds).
For purposes of this disclosure, the terms “spacer molecule,” “spacer compound,” and “linker” molecules (i.e., second molecules) are used synonymously.
For the purposes of this disclosure, the terms “terminal groups” or “terminal moieties” can refer to such groups that are derived from listed examples. For example, where ethanolamine is referred to as a terminal group, the terminal group can also be referred to as an ethoxyaminyl group or an aminoethoxyl group. Additionally, “terminal group” or “terminal moiety” is synonymous with “terminal moiety forming molecule.”
In various examples, the functionalization of silicon membranes (e.g., nanomembranes) modifies the membrane (e.g., nanomembrane) surface properties for particular applications. For example, the terminal group is a group that promotes non-fouling of the membrane by maintaining a hydration layer (e.g., hydroxyl groups or zwitterionic groups) or by a hydrophobic surface (e.g., perfluorinated groups), wherein either terminal groups prevent non-specific absorption of molecules or blood components. Further, the chemical properties of the hydration layer may reduce surface tension, thus promoting the wetting ability of functionalized membranes.
As an example of functionalization of a silicon membrane (e.g., nanomembrane) with a non-fouling terminal group, a membrane (e.g., nanomembrane) is chemically oxidized, reacted with epichlorohydrin, and then reacted with ethanolamine to provide a functionalized silicon membrane (e.g., nanomembrane). As another example, a membrane (e.g., nanomembrane) is chemically oxidized, reacted with epichlorohydrin, and then reacted with amine-polyethyleneglycol (PEG) to provide a functionalized silicon membrane (e.g., nanomembrane). As another example, a membrane (e.g., nanomembrane) is hydrofluoric acid (HF) treated and then reacted with glyceraldehyde to provide a functionalized silicon membrane (e.g., nanomembrane). As another example, a membrane (e.g., nanomembrane) is HF treated, reacted with glutaraldehyde, and then reacted with ethanolamine to provide a functionalized silicon membrane (e.g., nanomembrane). In all such examples, the terminal group comprises one or more hydroxyl groups. In these examples, use of any required acid/base catalyst or reductive amination agent is assumed. Of course, many other examples are possible.
In an example, the non-fouling group has a range of linear or branched groups. Such linear or branch groups (e.g., aliphatic groups) are homogenous (e.g., containing only carbon and hydrogen) or heterogeneous (e.g., containing carbon, hydrogen, and other heteroatoms (e.g., oxygen, sulfur, nitrogen, and the like)) in composition and structural arrangement, and comprises, for example, one or more linear or branch chains (e.g., aliphatic chains). Further, such non-fouling groups may be terminated or substituted with one or more functional groups that endow non-fouling properties (e.g., hydroxyl groups, zwitterions, hydrophobic, and the like) and should not decrease mean pore diameter or slit width by more than 10% (i.e., for every 50 nm of pore diameter or slit width, the linear or branched aliphatic (e.g., alkyl) chains should be less than 20 carbons in length). Non-limiting examples of non-fouling groups include ethanolamine, ethylene and polyethylene glycols and co-polymers thereof, vinyl alcohols or pyridines and polymers thereof, perfluorinated or other terminal fluorine presenting groups and polymers thereof, and the like. Additional non-limiting examples of non-fouling groups include sulfobetaine and analogs and derivatives thereof, Fmoc-lysine, hydroxylamine-O-sulfonic acid, 3-(amidinothio)-1-propanesulfonic acid, 6-carbon to 8-carbon long terminal aldehydes with heavily fluorinated aliphatic (e.g., alkyl) chains, or perfluorooctanesulfonamide. Fmoc-lysine comprises a fluorenylmethyloxycarbonyl (i.e., Fmoc) protective group at the C1 (alpha) position amine such that reaction to the modified reactive surface groups may occur at the C5 (epsilon) amine group of lysine (e.g., Fmoc subsequently deprotected in N, N-dimethylformamide with piperidine). Another example zwitterionic terminal group may be H2N-Lys-Glu-Lys-CO2H tripeptide (where the C5 (epsilon) lysine side-chains and C-terminus are functionalized with protecting groups) as a larger zwitterion and hydrogen bonding moiety.
In an example, the non-fouling coating prevents surface adsorption of interfering species via a gradual release of the one or more compounds (e.g. anticoagulants such as sodium heparin or citrate, and the like) by, for example, selective degradation of the film or structural rearrangement of the film to achieve dissipation of incorporated species by one or more mechanisms (e.g. dissolution, depolymerization, temperature or pH-induced structural changes, or other mechanisms).
For purposes of this disclosure, the functionalization of membranes (e.g., nanomembranes) with aliphatic (e.g., alkyl) containing terminal groups should be considered indirect covalent bonding via any of the functionalization reactions described herein. The modification with aliphatic (e.g., alkyl) containing terminal groups is not direct but rather indirect, wherein any aliphatic or alkyl containing group is reacted with the functionalization groups disclosed herein (e.g., epihalohydrin or bifunctional aldehyde or silane) and not reacted directly with chemically-activated membrane (e.g., nanomembrane) surface reactive groups (e.g., —OH, —NH2, and the like).
In other examples, the optional terminal group is also a surface property modifying group, such as a charged, non-polar, or amphiphilic group, such that the functionalization of silicon membranes with such terminal groups forms a coating wherein the surface properties of the silicon membrane correspond to those of these additional terminal group examples. These additional terminal groups can be linear, branched, or possess one or more charged, non-polar, or amphiphilic groups. Non-limiting examples of such groups may include linear and branched aliphatic groups (e.g., alkyl, alkenyl, and the like), primary, secondary, and tertiary amines having various aliphatic linear or branched groups covalently bonded thereto, carboxylates or sulfonates having various aliphatic linear or branched groups covalently bonded thereto, canonical amino acids such as alanine, leucine, isoleucine, valine, histidine, arginine, lysine, glutamate, aspartate, and the like, and non-canonical amino acids, such as, for example, ornithine, selenocysteine, fluorinated phenylalanine (e.g., pentafluorophenylalanine, p-fluorophenylalanine, and the like), and the like.
In various examples, the terminal groups are a mixture of non-fouling and surface property modifying groups.
In various examples, performing any of the reactions disclosed herein comprises contacting the membrane (e.g., nanomembrane) with either solution-phase and/or gas-phase reactant molecules, solutions comprising one or more reactants, or any combinations thereof.
The activation or treatment of the membrane surface by solution-phase chemistries, where reactive surface groups are formed, may be selected such that they are compatible with one or both silicon nitride (SiN) and/or silicon oxide (SiO2) membranes (e.g., nanomembranes), as disclosed herein.
In an example, the functionalization methods are performed selectively, such that the entirety of a silicon membrane (e.g., nanomembrane) surface (e.g., on two (e.g., both) of its sides) are modified. In another example, only one of the membrane's (e.g., nanomembrane's) surfaces is selectively modified, while the opposing membrane surface remains unmodified. Further, the nanoporous, microporous, or microslit features of the membranes (e.g., nanomembranes) can be selectively functionalized within their intra-pore or intra-slit surfaces (e.g., the internal surface of a cylindrical nanopore and a micropore or the internal walls of a cubic prism microslit), while any other surface of the membrane (e.g., nanomembrane) remains unmodified or is selectively modified on one or more such surfaces. As a further alternative, the surface walls of the substrate aperture are selectively modified, while the other features of the membranes (e.g., nanomembranes) remain unmodified. Such functionalization methods may be performed on monolithic membranes (e.g., nanomembranes) as described herein.
As an example, any surface, pore, or slit feature is selectively masked such that the masking prevents functionalization, while unmasked surfaces are functionalized. For example, the masking comprises use of a photoresist, where the photoresist is disposed onto the first membrane surface of a microporous or microslit membranes (e.g., nanomembranes), such that any pore or slit features are not masked; i.e., the porous or slit features remain open and are not disposed by these coatings on their intra-pore or intra-slit surfaces. Subsequent to the disposition of the photoresist, any one of the functionalization methods disclosed herein may be used to modify the intra-pore or intra-slit surfaces, followed by removal of the photoresist in an appropriate solvent (e.g., acetone, developer solution, or toluene). The functionalization method would be selective for the unmasked membrane (e.g., nanomembrane) features such that it does not modify the photoresist. Alternatively, if the functionalization method should happen to modify the photoresist, such modified photoresist would be removed post-functionalization to expose an unmodified first membrane surface. Further, the photoresist can be selectively removed without disrupting the functionalized surface, pore or slit. Of course, other possible combinations of selective masking and/or functionalization may be carried out with any degree of iteration of surface, pore, and/or slit, and the above example has been provided for exemplary purposes only.
In an example, a method for functionalizing a silicon membrane (e.g., nanomembrane) comprises: contacting a membrane (e.g., nanomembrane) with a chemical oxidation solution; contacting the membrane (e.g., nanomembrane) with gas-phase epihalohydrin molecules; contacting the membrane (e.g., nanomembrane) with solution-phase acid or base catalysts; and contacting the membrane (e.g., nanomembrane) with gas-phase and/or solution-phase terminal moieties.
The chemical oxidation solution may comprise a solution of 80% w/v sulfuric acid (H2SO4) and 30% v/v hydrogen peroxide (H2O2), at a mixed ratio, respectively, of 3:1 to 20:1, including all integer ratio values and ranges therebetween. Such a mixed solution may be referred to as piranha solution. Alternatively, the chemical oxidation solution may comprise an aqueous solution of deionized water, 29% w/v ammonium hydroxide (NH4OH), and 30% v/v (H2O2, at a mixed ratio, respectively, of 5:1:1 to 8:0.5:1, including all integer ratio values and ranges therebetween. Such a solution may be referred to as RCA SC1 solution. Such chemical oxidation solutions likely form hydroxyl surface groups on SiN and SiO2 membranes (e.g., nanomembranes) (i.e., Si—OH bonds). Contact with the chemical oxidation solution may be performed at a range of temperature and time duration. For example, contact with the solution may be from 25° to 150° C., including all 0.1° C. and ranges therebetween. The time duration may be from 1 to 20 minutes, including all 0.01 minute values and ranges therebetween. Concentration of any solution component, temperature, and time duration are likely to affect the extent of surface hydroxyl group formation.
The epihalohydrin molecules (i.e., epihalohydrins) may comprise epichlorohydrin or epibromohydrin molecules. The epoxide group of such epihalohydrins may react with the hydroxyl groups of the chemically oxidized membrane (e.g., nanomembrane), the reaction mechanism of which is known in the art. Gaseous epihalohydrin may be formed at a range of vapor pressure and/or temperature. For example, the vapor pressure may be 1.3 to 2666.5 Pascal, or any 0.01 Pascal value and range therebetween. The temperature may be 25° to 100° C., including all 0.1° C. and ranges therebetween. Contact of the membrane (e.g., nanomembrane) with the gaseous epihalohydrin may also be performed at a range of time duration; e.g., from 1 minute to 16 hours, including all 0.01 minute values and ranges therebetween. Vapor pressure, temperature, and time duration may likely affect the extent to which the membrane (e.g., nanomembrane) is derivative by the epihalohydrin.
The solution-phase acid or base catalysts may comprise an aqueous solution of a Lewis acid or Lewis base at a range of concentration and may promote the re-closure of the epoxide ring and removal of the halogen leaving group For example, the acid or base catalyst may comprise deionized water, 0.1% to 10% v/v hydrochloric acid (HCl), including all 0.1% values and ranges therebetween, 0.1% to 10% v/v sodium hydroxide (NaOH) or potassium hydroxide (KOH), including all 0.1% values and ranges therebetween. The acid or base catalysis may comprise a range of temperature and time duration. For example, the temperature is from 25° to 100° C., including all 0.1° C. and ranges therebetween, and the time duration may be from 1 minute to 60 minutes, including all 0.01 minute values and ranges therebetween. Such catalysts are likely to promote the removal of the halogen leaving group and re-closing of the epoxide ring, as known to those skilled in the art.
In some examples, a solution-phase or gas-phase spacer molecule is reacted with the epihalohydrin-reacted membrane (e.g., nanomembrane) prior to reacting said membrane (e.g., nanomembrane) with terminal moieties. The spacer molecule may comprise at least one amine group that reacts with the epoxide functional group of said treated membrane (e.g., nanomembrane) and at least one additional reactive group that reacts with one or more terminal moieties. In an example, the spacer molecule is glutaraldehyde, but many other possible spacer molecules could be used.
In another example, a method for functionalizing a silicon membrane (e.g., nanomembrane) comprises:
The chemical oxide etchant solution may comprise an aqueous solution of hydrofluoric acid (HF) or buffered-oxide etchant (BOE, either of which selectively etches native surface SiO2 on SiN and further forms surface amine groups (i.e., Si—NH2). The aqueous solution of HF may comprise a range of concentration (e.g., 48% v/v HF may be diluted in deionized water to 0.1% to 10%, including all 0.1% values and ranges therebetween). Alternatively, BOE solutions may comprise a solution of deionized water, 40% v/v ammonium fluoride (NH4F) and 48% v/v HF, at a mixed ratio, respectively, of 5:1:1 to 50:1:1, including all ratio values and ranges therebetween. As appreciated by those skilled in the art, such chemical oxide etchants would be incompatible with SiO2 membranes (e.g., nanomembranes), and thus, this exemplary functionalization method is intended for SiN membranes (e.g., nanomembranes). Contact with the chemical oxide etchant solution may be performed at a range of temperature and time duration. For example, contact with the solution may be from 25° to 60° C., including all 0.1° C. and ranges therebetween. The time duration may be from 30 seconds to 3 minutes, including all 0.01 minute values and ranges therebetween. Concentration of solution components, temperature, and time duration are likely to promote extent of native oxide removal and amine group formation.
The aldehyde molecules (i.e., aldehydes) may comprise linear or branched aliphatic (e.g., alkyl) groups with 1-18 carbons with any degree of branching, and one or more terminal aldehyde groups (e.g., glutaraldehyde, or halogenated or hydroxylated substitutions and one or more terminal aldehyde groups (e.g., glyceraldehyde or other aliphatic groups (e.g., alkyl groups) that are terminated with at least one aldehyde and one or more hydroxyl substituents)). Reaction of the aldehyde groups with surface amine groups likely follows a reaction mechanism well-known to those skilled in the art; e.g., a reaction of the aldehyde and amine likely produces a Schiff base imine. The imine may be further reduced in order to promote its hydrolytic stability in the form of an amine that is linked to the membrane (e.g., nanomembrane) surface (i.e., Si—N—C bonds).
The gas-phase aldehydes may be formed at a range of vapor pressure and/or temperature. In various examples, the vapor pressure is 1.3 to 2666.5 Pascal, including all 0.1 Pascal values and ranges therebetween, and/or the temperature is 25° to 200° C., including all 0.1° C. values and ranges therebetween. Contact of the membrane (e.g., nanomembrane) with solution-phase aldehydes may comprise a range of concentration and/or temperature. For example, the aldehyde concentration is 1 μM to 10 M, including all integer μM values and ranges therebetween, and/or the temperature is from 25° to 100° C., including all 0.1° C. values and ranges therebetween. For both solution-phase and gas-phase aldehydes, the contact may be performed at a range of time duration; e.g., from 1 minute to 16 hours, including all second and minute values and ranges therebetween. Vapor pressure, concentration, temperature, and time duration may likely affect the extent to which the membrane (e.g., nanomembrane) is derivatized by the aldehyde.
The contact with the aldehydes may further comprise use of a dehydrating agent; e.g., a molecular sieve, magnesium sulfate, tris(2,2,2-trifluoroethyl)borate, or titanium ethoxide, and the like. Such dehydrating agents may promote formation of the Schiff base amine, as the equilibrium of amine formation from aldehydes and amines may favor the carbonyl compound and the amine reactants.
The solution-phase reductive amination agents may comprise an aqueous solution of, for example, sodium borohydride (NaBH4), sodium cyanoborohydride (NaBH3CN), or sodium triacetoxyborohydride (NaBH(OCOCH3)3), and the like. Such agents may be at a range of concentration; e.g., 1 μm to 1 mM, including all 0.1 μM values and ranges therebetween. The reductive amination may be performed at a range of temperature (e.g., 25° to 100° C., including all 0.1° C. values and ranges therebetween) and/or for a range of time duration (e.g., 1 minute to 60 minutes, including all integer second values and ranges therebetween).
In a further example, a method disclosed herein is combined with well-known silane functionalization methods, such that the combination improves the density of surface functionalization coverage, and therefore, may improve the hydrolytic stability of the silane-functionalized surface. Such combined functionalization methods may rely upon selective mechanisms and reactive groups for the one or more functionalization methods. For example, the method disclosed herein for amine group functionalization (e.g., aldehyde reactions) may be combined with a method for hydroxyl group functionalization (e.g., silane reactions).
In various examples of the combined functionalization method, the molecular size of the aldehyde derivative should be specified such that it does not sterically hinder further surface derivatization with the silane derivative. Further, it is desirable that the size of the silane derivative be specified such that it is not sterically hindered by the preceding derivatization of the membrane (e.g., nanomembrane) with the aldehyde derivative. Thus, the number of atoms (e.g., number of atoms in an aliphatic group (e.g., methylene groups (e.g., carbons)) in a chain), number of reactive functional groups, and/or extent of chain branching may be specified for both the aldehyde and silane derivatives. For example, the aldehyde comprises two reactive groups and a five-carbon aliphatic (e.g., alkyl) chain, while the silane comprises one reactive group, two leaving groups, and a two-carbon aliphatic (e.g., alkyl) chain that further branches at the terminal carbon with two methyl groups. Other combinations of which are known in the art. In an example, the silicon membrane (e.g., nanomembrane) is not functionalized solely with a silane.
In a further example, a method for a combined functionalization of a silicon membrane (e.g., nanomembrane) comprises: contacting a membrane (e.g., nanomembrane) with a chemical oxide etchant solution; contacting the membrane (e.g., nanomembrane) with solution-phase or gas-phase aldehyde molecules; contacting the membrane (e.g., nanomembrane) with solution-phase reductive amination agents; contacting the membrane (e.g., nanomembrane) with solution-phase or gas-phase silane molecules; and optionally, contacting the membrane (e.g., nanomembrane) with gas-phase and/or solution-phase terminal moieties.
In examples of a combined functionalization, the method for contacting a membrane (e.g., nanomembrane) with solution-phase and/or gas-phase chemical oxide etchants, aldehydes, and reductive amination agents comprises the steps disclosed herein for such contacting steps when only aldehyde-based functionalization is been performed.
The solution-phase or gas-phase silane molecules may comprise, for example, chloro(dimethyl)(pentafluorophenyl)silane or chloro(dimethyl)silyl trifluoromethanesulfonate, and the like, that may comprise their own inherent terminal moieties with non-fouling properties. The solution-phase or gas-phase silane molecules may further comprise a first reactive group that reacts with the substrate surface hydroxyl groups and a second reactive group that reacts with optional terminal moieties as disclosed herein, such silanes acting as spacer molecules and may include, for example, ethyl 3-[chloro(dimethyl)silyl]acrylate or (3-glycidoxypropyl)trimethoxysilane, and the like.
The gas-phase silane molecules may be formed at a range of vapor pressure and/or temperature. In various examples, the vapor pressure is 1.3 to 2666.5 Pascal, including all 0.1 Pascal values and ranges therebetween and/or the temperature is 25° to 200° C., including all 0.1° C. values and ranges therebetween. Contact of the membrane (e.g., nanomembrane) with solution-phase silane molecules may comprise a range of concentration and/or temperature. For example, the silane molecule concentration is 1 μM to 10 mM, including all 0.1 μM values and ranges therebetween and/or the temperature is from 25° to 100° C., including all 0.1° C. values and ranges therebetween. For both solution-phase and gas-phase silane molecules, the contact may be performed at a range of time duration; e.g., from 1 minute to 16 hours, including all integer second values and ranges therebetween. Vapor pressure, concentration, temperature, and time duration may likely affect the extent to which the membrane (e.g., nanomembrane) is derivatized by the silane.
In some examples of the combined functionalization method, an optional oxidation step precedes contact with the silane(s). For example, a rinse in deionized water for 1 to 10 minutes at 25° to 100° C., including all 0.1° C. values and ranges therebetween, is used to re-form substrate surface hydroxyl groups. Such hydroxyl groups may be removed by oxide etchants, thus, increasing their density may improve the extent to which silanes derivatize the membranes (e.g., nanomembranes) in subsequent reactions.
In the various examples, contact with the solution-phase and gas-phase reactants is sequentially performed or concurrently performed in any combination of the various steps. The steps are performed in suitable reaction vessels for such reactions (e.g., specified volume and surface properties, temperature control, fluidic valves for adding and removing reactants, pumps for controlling vapor pressure, and the like). Further, any of the sequentially and/or concurrently performed steps may be carried out in one common vessel (to which various reactants are added and removed as required for carrying out the method) or in a series of independent vessels (to which various reactants are added and removed and silicon membranes (e.g., nanomembranes) transferred between such vessels, to carry out the method).
In the various examples, optional rinsing or cleaning steps precede or follow any of the steps disclosed herein. Such rinsing or cleaning steps may be performed to remove any chemisorbed or physisorbed reactants and/or reaction products, and the like. The rinsing and cleaning may be carried out with a variety of polar or non-polar solutions; e.g., water, acetone, toluene, dichloromethane, hexane, ethanol, methanol, and the like. Further, an optional drying step may precede or follow any of the steps disclosed herein. For example, membranes (e.g., nanomembranes) may be functionalized by a method of the present disclosure, optionally rinsed in ultra-pure water, then dried under a stream of anhydrous nitrogen gas. Of course, many other possibilities for such optional rinsing, cleaning, and drying steps are possible.
In the various steps of the method disclosed herein, the reaction is monitored by one or more suitable metrology modalities; e.g., variable angle ellipsometry, x-ray photoelectron spectroscopy ( )PS), low-energy ion scattering (LEIS), atomic force microscopy (AFM), scanning or transmission electron microscopy (SEM or TEM), contact angel goniometry, infrared absorption spectroscopy (IRAS), and the like.
In an aspect, the present disclosure describes fluidic devices incorporating at least one functionalized silicon membrane (e.g., nanomembrane) and uses of such fluidic devices. For example, a fluidic device is used for filtration applications or methods.
In various examples, a fluidic device comprises at least one functionalized silicon membrane (e.g., nanomembrane), and further comprises a plurality of fluidic channels or chambers (e.g., a first fluidic channel or chamber, a second fluidic channel or chamber, etc.) in fluidic contact with a plurality of membrane surfaces (e.g., a first membrane, a second membrane, etc.), such as, for example, a first fluidic channel or chamber in fluidic contact with a first membrane surface and at least one second fluidic channel or chamber in fluidic contact with the at least one second membrane surface and one or more aperture, and the plurality of fluidic channels and/or chambers (e.g., a first and second fluidic channels and/or chambers) in fluid contact with each other via the aperture and the nanopores, micropores, or microslits, of the membrane.
In various examples, a fluidic devices comprises a first fluidic channel and/or chamber in fluidic contact with the silicon substrate; a second fluidic channel and/or chamber in fluid contact with the membrane (e.g., nanomembrane); and wherein the first fluidic channel and/or chamber is in fluidic communication with the second fluidic channel by way of the aperture and the plurality of nanopores, micropores, or microslits of the membrane. In various examples, a first plurality of fluidic channels and/or chambers are in fluidic contact with a silicon substrate (e.g., silicon wafer); a second plurality of fluidic channels and/or chambers are in fluidic contact with the membrane (e.g., nanomembrane), wherein the first plurality of fluidic channels and/or chambers are in fluidic communication with a second plurality of fluidic channels and/or chambers by way of an aperture and a plurality of nanopores, micropores, or microslits.
In various examples, wherein one or more additional apertures extend through the thickness of the silicon substrate, and wherein the first fluidic channel and/or chamber (or plurality thereof) is further in fluidic communication with the second fluidic channel and/or chamber (or plurality thereof) by way of the one or more additional apertures.
In various examples, a method of performing a filtration comprises: contacting an input solution with a functionalized silicon membrane, where the input solution contacts at least one first membrane surface of a membrane; and, collecting a volume of the input solution that permeates through the membrane, where the volume is collected on the opposing at least second membrane surface and/or at least one aperture.
In an example, contacting the input solution with the at least one first membrane surface comprises normal or tangential flow relative to said membrane surface, where such flow comprises one of gravity flow, hydrostatic pressure, pumping, vacuum, centrifugation, gas pressurization, or combinations thereof. In another example, the method further comprises contacting the at least one second membrane surface and/or at least one aperture with an optional second solution during collection of the permeating volume of the input solution.
In other examples, contacting the at least one second membrane surface and/or at least one aperture with an optional second solution further comprises flowing the optional second solution parallel with, perpendicular to, or counter to, the flow of the input solution. In this example, permeation of solutes from the input solution to any optional second solution or permeation of solutes from any optional second solution to the input solution may occur.
In an example, the filtration device (e.g., fluidic device) is a system configured to perform hemodialysis, where blood passes over one surface of the silicon membrane functionalized with a non-fouling coating, and a counter-flowing dialysate solution passes over the opposite surface of the silicon membrane. It is expected that such a filtration device could be part of a treatment for end-stage kidney disease. The non-fouling coating on the functionalized silicon membrane would be required for the prevention of non-specific absorption of blood constituents onto the membrane, for the prevention of clot formation, activation of platelets, and the like. Such a filtration process may be described as a tangential flow filtration process, wherein solutes permeate from blood to dialysate (and vice versa) during the course of filtration.
In an example, the filtration device (e.g., fluidic device) is a system configured to perform a routine separation, where an input solution contacts the silicon membrane functionalized with one or more coatings of the present disclosure. In routine separations, a volume of the input solution permeates through the membrane and can be collected on the opposing side of the membrane. Additionally, a dialysate or buffer can be added to either the input solution and/or the opposing side of the membrane during the course of the filtration. Such routine separations can be used to separate various solutes based on size and other physical properties (e.g., charge or hydrophilicity/hydrophobicity) and can be used to retain certain solutes, concentrate solutes, and/or exchange the buffer or other components of the input solution with those of the added dialysate or buffer.
In various examples, these routine separations are performed as a tangential flow filtration process, where solutes permeate from the input solution to any optional buffer or dialysate added to the second side of the membrane (and vice versa) during the course of filtration. As another example, the filtration device could be a dead-end or normal flow filtration device, where solutes from the input solution selectively permeate from the first side of the contacting silicon membrane to the opposing side of the contacting silicon membrane. In both tangential and normal flow examples, the one or more coating on the functionalized silicon membrane would be required for the prevention of non-specific absorption of solution constituents, promoting the wetting of the membrane, and/or modulating the selective separation properties of the membrane.
In an example of a routine separation, the tangential or normal flow filtration devices are used to perform separations of size-specific fractions of laboratory solutions, such as those comprising analytical-scale volumes and concentrations of proteins, cells, or nucleic acids (and the like). In yet another example, the tangential or normal flow filtration devices are used to perform separations of size-specific fractions of clinical solutions, such as whole blood, prepared blood products, or preparations thereof (e.g., erythrocytes, leukocytes, platelets, plasma, serum, and the like), cerebral spinal fluid, urine, and other endogenous biofluids not specifically named. In yet another example, the tangential or normal flow filtration devices are used to perform separations of industrial solutions, such as chemical, pharmaceutical, synthetic, recombinant or naturally derived proteins, viruses or cells, and food, and the like.
In an example, the filtration device (e.g., fluidic device) is a system configured to perform a sterile filtration, where an input solution contacts the silicon membrane functionalized with one or more coatings of the present disclosure. In a sterile filtration, a volume of the input solution permeates through the membrane and can be collected on the opposing side of the membrane. Additionally, a sterile dialysate or buffer can be added to either the input solution and/or the opposing side of the membrane during the course of the filtration. Of particular importance for sterile filtration, the filtration can be used to retain possible microbial contaminants (e.g., microbes, such as, for example, viruses, bacteria, fungi, and the like) from the input solution, based on physical properties (e.g., size, charge or hydrophilicity/hydrophobicity of the microbes), and further to permeate a volume of the input solution that is substantially devoid of any such microbes and thus is considered a sterilized solution. Further, solutes may co-permeate with the permeating volume of input solution that passes through the membrane and thus may be considered sterilized solutes. Such solute permeation may be based on their physical properties (e.g., size, charge or hydrophilicity/hydrophobicity).
In various examples, sterile filtration can be performed as a tangential flow filtration process, where microbes are retained and the volume and the solutes of the input solution permeate from the input solution to any optional buffer or dialysate added to the second side of the membrane during the course of filtration. As another example, the filtration device could be a dead-end or normal flow filtration device, where the volume and the solutes from the input solution selectively permeate from the first side of the contacting membrane to the opposing side of the contacting membrane, while any microbes are retained on the first side of the contacting membrane. In both tangential and normal flow examples, the one or more coating on the functionalized silicon membrane would be required for the prevention of non-specific absorption of solution constituents, promoting the wetting of the membrane, and/or modulating the selective separation properties of the membrane.
In an example of sterile filtration, the tangential or normal flow filtration devices are used to perform sterilization of laboratory solutions, such as those comprising analytical-scale volumes and concentrations of conditioned cell culture media, ascites fluid, proteins, nucleic acids, lipids, cells, viruses, extracellular vesicles, nanoparticles, and any combinations thereof, among other examples. In yet another example, the tangential or normal flow filtration devices are used to perform sterilization of clinical solutions, such as whole blood, prepared blood products, extracellular vesicles, or preparations thereof (e.g., erythrocytes, leukocytes, platelets, plasma, serum, and the like), cerebral spinal fluid, urine, and other endogenous biofluids not specifically named. In yet another example, the tangential or normal flow filtration devices are used to perform sterilization of industrial solutions, such as chemical, pharmaceutical, synthetic, recombinant or naturally derived proteins, viruses or cells, milk, food products, nanoparticles, antibody-drug conjugates, and the like. In yet other examples, one or more of the sterile filtered laboratory, clinical, and/or industrial solutions are combined as a product for various applications, purposes, and needs.
In an example of performing a sterile filtration, the solutes to be sterilized by permeation through a functionalized silicon membrane of the present disclosure may comprise a solute intended for use in clinical applications; e.g., the solute should be sterilized as part of formulating an injectable therapeutic agent. For example, the solute may be a solution of extracellular vesicles (e.g., exosomes or the like) that should be sterilized for use as a drug delivery or vaccination vehicle. In another example, the solute may be a solution of nanoparticles or antibody-drug conjugates, wherein the nanoparticles or antibody-drug conjugates have been engineered, for example, as drug delivery vehicles, therapeutics, or as genetic engineering vectors, and thus should be sterilized for use as an administrable therapeutic agent. In yet another example, the solute is a solution of one or more naturally-occurring viruses and/or one or more viruses that have been engineered, for example, as oncolytic, gene therapy, or vaccination agents, and thus should be sterilized for use as an administrable therapeutic agent. In such examples involving viruses, the desired permeating solute is the virus in monomeric form that has been filtered from possible contamination by other microbes and/or aggregates of the same virus in multimeric forms.
In a preferred example of a sterile filtration, the functionalized silicon membrane (e.g., nanomembrane) may comprise a microslit silicon nitride membrane of 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, or 0.8 μm width. In a preferred example, the functionalized silicon membrane (e.g., nanomembrane) has a microslit width of 0.2 μm to 0.4 μm, including all integer 0.01 μm values and ranges therebetween. In another example, the functionalized silicon membrane (e.g., nanomembrane) has a microslit width of 0.2 μm to 0.8 μm, including all integer 0.01 μm values and ranges therebetween. Notwithstanding these preferred examples, other nanoporous or microporous silicon membranes as disclosed herein can be used for sterile filtration. The steps of the method described in the various embodiments and examples disclosed herein are sufficient to carry out the methods of the present disclosure. Thus, in an embodiment, a method consists essentially of a combination of steps of the methods disclosed herein. In another embodiment, a method consists of such steps.
In the following Statements, various examples of the present disclosure are described:
a first fluidic channel and/or chamber in fluidic contact with the silicon substrate;
a second fluidic channel and/or chamber in fluid contact with the nanomembrane; and
where the first fluidic channel and/or chamber is in fluidic communication with the second fluidic channel by way of the aperture and the plurality of nanopores, micropores, or microslits of the membrane.
The following examples are presented to illustrate the present disclosure. They are not intended to be limiting in any matter.
This example provides a description of preparation and characterization of functionalized of silicon nanomembranes of the present disclosure.
Chemistry Deposition System development and testing. This examples describes gaseous phase surface derivatization process for low-stress SiN membrane substrates. Additionally, surface decoration will be monitored by subsequent interaction with reactive species.
Materials. Chemicals used for surface functionalization included 3-(triethoxysilyl)propyl Isocyanate, (+/−) epichlorohydrin, ethanolamine, toluene (Anhydrous), N-propanol, dimethyl sulfoxide (DMSO), and Fluorescein Isocyanate Isomer 1 were used as received from Sigma Aldrich at ASC grade or better.
Experiment Setup. A basic vacuum deposition system was fabricated from off-the-shelf components. Images of the system used are attached for reference. Briefly, a vacuum source (mid-range rotary vane pump) is connected via inline vapor trap (pre-loaded with molecular sieves) to a polycarbonate desiccator dome (Nalgene Inc.). Inside the dome was placed a sample holder (entirely polypropylene construction), elevated ˜3″ from the chamber bottom to promote ideal gas flow to the samples. The dome inlet supplies (vie straight wye) either 0.2 micron filtered atmosphere vent or chemistry vapor generated from a borosilicate glass tube (25 mL capacity). Both inlet types are individually controlled via full-port ball valves. A pressure gauge (VWR brand, NIST traceable) is used to monitor system pressure inline to the chemistry flask. After assembly the system was leak checked and is suitable for maintaining a 8 kPa vacuum for at least 24 hours.
Preparation of Substrates. A 4″ SiN coated double-side polished wafer was used as the source material for all experiments. Individual die were cleaved into ˜1 cm2 surface are substrates and held in glass dishes until use. All substrates used in deposition experiments were cleaned using a standard Piranha wash (3:1 H2SO4:H2O2) for 1 hour at RT, then rinsed in excess with nanopure 18.6 MΩ water and used immediately.
Deposition of Epichlorohydrin. Substrates (prepared as above) were placed on the sample holder in the dome, then the system was evacuated of atmosphere to at least 8 kPa. Following which 2 grams of epichlorohydrin was allowed to vaporize from the chemistry flask at RT over a period of 2 hours as follows:
During this process all of the liquid chemistry was converted to a vapor at RT conditions. Following deposition substrates were recovered from the sample holder and stored in pre-cleaned glass dishes until use.
Deposition of Isocyanate Silane. A series of substrates were prepared as above and collected in a toluene-cleaned glass dish. To these substrates a solution of 10% 3-(triethoxysilyl)propyl Isocyanate (NCO-silane) in anhydrous toluene was added and allowed to react for 2 hours at room temperate with no agitation. Following deposition sensors were rinsed extensively in the dish with fresh toluene, then transferred to a new toluene-containing dish, further rinsed with 2× fresh toluene fractions, then sonicate for 5 minutes to remove nonspecifically adsorbed silane species. After sonication, the waste toluene was displaced with N-propanol via several successive fraction rinses, then each substrate was rinsed under N-propanol stream and N2 dried. Substrates were collected in a clean glass dish until use.
Verification of Surface Chemistry Reactivity. To verify the surface reactivity of both epoxide and isocyanate derivatized substrates, solutions of ethanolamine and BSA were prepared and allowed to incubate overnight at RT with 250 RPM agitation. Ethanolamine was deposited from a 100 mM solution containing 50 mM borate pH 9.0 whereas BSA was deposited from a 1% solution in PBS pH 7.4. After deposition both solutions were displaced with a wash buffer containing PBS augmented with 0.05% Tween-20 and 5 mM EDTA pH 7.4 (PBS-ET) for 30 minutes at RT with 250 RPM agitation. After washing substrates were individually rinsed under freshly prepared nanopure water stream and N2 dried.
Fluorescent labeling of surfaces. As a verification of the presence of BSA on each surface type, the surface-bound BSA was fluorescently labeled for later quantitation. A solution of 200 μg/mL FITC isomer 1 was first prepared as a 6 mg/mL solution in DMSO then diluted into 50 mM sodium borate pH 9.0. This solution was then applied from bulk to all substrates and allowed to react for 2 hours with 250 RPM agitation. Following deposition, substrates were individually rinsed in borate buffer then nanopure water and finally dried under N2 stream.
Contact angle measurements. Sessile water contact angle measurements were collected in triplicate per sensor substrate via deposition of a 2 μL droplet of freshly prepared 0.2 μm filtered nanopure water, then imaged use a USB camera and MicroCapture Pro. Images were then analyzed further in image J for sessile contact angles and post processed using Microsoft Excel.
Fluorescent Intensity Measurement. Surface fluorescence profiles were collected for all conditions via mounting of substrates onto a black 384-well plate pre-coated with a 300 μm silicone gasket to prevent motion of substrates during plate manipulation. Fluorescent intensity was collected via an 13 multimode plate reader and SoftMax Pro 6.3 using a 16-point per well scan of each well, where each substrate covers ˜2.5 wells, yielding at least 32 points per substrate.
The vacuum deposition system fabricated yielded expected performance given the low-cost vacuum pump utilized. Curiously a ˜8 kPa vacuum was suitable for vaporizing the chemistry used in this work, likely due to partial pressure combined with continual evacuation of the chamber during dehalogenation through the second hour of the reaction. Initial film deposition performance was only monitored using water contact angle, a limitation of this study. The results for this assessment are presented as
As further verification of the presence of covalently tethered serum albumin, the free amines of the protein were further decorated with FITC. This process, after analysis, yielded a considerable increase in MFI for the BSA-treated substrates, with no appreciable MFI change for the ethanolamine passivated substrates relative to the native film controls.
These data demonstrate a system and process has been constructed and tested suitable for the vapor-phase functionalization of SiN surfaces by an epoxide terminal species. Additionally, the silylation of low-stress SiN has been demonstrated using a model amine-reactive alkoxy silane. Both films produced demonstrate sufficient density to affect a water contact angle change and are sufficiently reactive to amine containing compounds by measurement via the former.
This example provides a description of preparation and characterization of functionalized of silicon nanomembranes of the present disclosure.
Non-fouling demonstration of ethanolamine terminated SiN. The following describes the non-fouling potential of ethanolamine derivatized SiN using an assortment of biofluids.
Methods. SiN Preparation. This Example utilized piranha cleaned SiN for all surface derivations. An overview of the functionalization process is provided below.
Substrate Cleaning. A SiN wafer was cleaved into ˜0.75 cm2 substrates, then cleaned via a standard 3:1 piranha recipe for 1 hour at RT. Following cleaning, chips were rinsed in bulk and then individually with freshly prepared 0.2 micron filtered 18.6 mOhm water and then dried under N2 stream.
Epoxide Functionalization. Using the vacuum deposition system (previously described), cleaned SiN die were transferred to the sample holder, then further dehydrated via a 10 min desiccation at 8 kPa. After which 2 grams of (±)-epichlorohydrin (Sigma 481386) was allowed to vaporize into the desiccator dome with the vacuum source isolated for 60 minutes. Following deposition, the chamber was purged to vacuum and allowed to further desiccate for an additional 60 minutes to promote dehalogenation of the surface-bound epichlorohydrin species.
Ethanolamine Deposition. A 10 mM ethanolamine solution was prepared in pH 9.0 Sodium Borate, then exposed to chips previously epoxide-functionalized for 60 minutes at RT in a toluene-cleaned borosilicate glass dish. Following exposure chips were rinsed with NanoPure water extensively and dried under N2 stream. Contact angle measurements were conducted throughout each step in the above process to ensure consistency with past deposition results.
Biofluid Exposure. After surface treatment, at least 3 chips were exposed to the following conditions: 1% BSA in PBS pH 7.4; 10% calf serum in PBS pH 7.4; and 100% calf serum.
Exposure was conducted in pre-cleaned glass dishes and occurred at RT for 24 hours using 250 RPM orbital agitation. As controls, piranha-cleaned and native SiN die were exposed to the identical solutions as above. Following exposure, chips were briefly rinsed in PBS, then NanoPure water, and dried under N2 stream.
Surface Labeling. To visualize non-specifically adsorbed protein species, all chips were labeled using a 1 uM solution of FITC prepared in pH 8.0 sodium borate for 1 hour. Following incubation with the fluorophore, chips were rinsed with NanoPure water and dried under N2 stream. Dry chips were then collected on a 384-well plate, then read using the well-scan mode of the I3 plated reader at excitation and emission wavelengths for Fluorescein. After which raw MFI was exported to Microsoft Excel for further analysis.
Sessile water contact angle measurements collected through the surface deposition process were consistent with past results for each surface treatment including native SiN (45°±1.8°), piranha cleaned SiN (<5°±2.4°), epichlorohydrin terminated SiN (52°±1.6°), and ethanolamine terminated SiN (22°±2.2°). Surface protein adsorption after 24 hour insult by either purified BSA, dilute serum, or neat serum as monitored by fluorescent labeling by FITC indicated the ethanolamine treatment tends to repel surface fouling for all solutions tested
These data demonstrate the resistance of ethanolamine-treated SiN to biofouling using a limited subset of solution types and exposure modalities. Indirectly, the prolonged non-fouling effects of the ethanolamine treated SiN indicates the linker chemistry is reasonably stable under aqueous buffered conditions for at least 24 hours of continual exposure. Further work is necessary to fully characterize both the reproducibility of surface treatment performance as well as robustness in manufacturing technique.
This example provides a demonstration of the biofouling reduction (i.e., non-fouling) effects of the surface treatment methods detailed herein.
In this example, fluorescently labeled serum albumin and whole sheep blood are used to insult treated or untreated nanomembrane surfaces. A dialysis experiment was run through a 4-membrane 100 nm chip using a flow cell device with concurrent-tangential flow, pulling volume at a flow rate of 150 μL/min with a peristaltic pump. A 1 mg/mL solution of Rhodamine-conjugated bovine serum albumin was prepared in 0.9% NaCl (saline solution). Two different nanomembrane surface treatment conditions were tested: 1) NPN nanomembrane coated in epichlorohydrin with ethanolamine as described in Example 2; and 2); 3) NPN membrane, left nominally untreated.
Before running the experiment all tubing and each device was primed with saline solution at a flow rate of 1 mL/min for approximately 10 minutes. Once primed, the device supply was changed to a media bottle containing the BSA solution. Rhodamine-BSA solution was recirculated through the device at flow rate of 150 μL/min through the membrane-containing device system. After 1 hour of concurrent flow, the chip was then removed from the system, briefly rinsed with a fraction of PBS and then freshly prepared 18MΩ water and dried under a stream of 0.2 μm filtered nitrogen. The chip was then analyzed via fluorescent microscopy using a Nikon Eclipse TS100 inverted fluorescence microscopy equipped with a standard TRITC filter cube and using 4× magnification. Images of all membrane surfaces were captured using an Amscope MU1203-FL camera system using a consistent gain and exposure settings for all conditions. Images were analyzed in Image J for Mean Fluorescent Intensity.
This second example demonstrated cell adhesion onto three different membrane surface types from whole sheep blood passed over the membrane surface. Using a flow cell device, several 4 slot 100 nm nanomembrane chips were exposed using concurrent-tangential flow in the methods described herein.
Nanomembranes were prepared as follows. Native piranha treated NPN (where the nanomembrane is cleaned with a standard piranha solution after fabrication at the wafer scale, otherwise called a control. NPN coated in epichlorohydrin with ethanolamine (where the nanomembrane is treated as described previously in Example 2). NPN that was rendered hydrophobic by extended exposure to PDMS via passive redeposition at 60° C. for 24 hrs.
Each nanomembrane was installed in a flow cell then fluidically connected to a peristaltic pump and tubing. Before running the experiment, all tubing and the nanomembrane containing flow cell device was primed with saline solution at a flow rate of 1 mL/min for approximately 10 minutes. Once primed, the device input was transferred to heparinized Whole Sheep Blood and the outlet tubing returned to the same media bottle. Sheep Blood was recirculated at a flow rate of 150 μL/min for 1 hour using concurrent flow. Each chip was then removed from the system, briefly rinsed with PBS and dried under a stream of nitrogen. The chip was then analyzed via phase microscopy using a Nikon Eclipse TS100 at 4× magnification/Images were captured using an Amscope MU1203-FL camera system. Following which, images were analyzed via Image-J do detect cells bound to the membrane using particle analysis. This process was repeated for all three conditions.
This example provides a description of exemplary fluidic devices and methods for their use in the present disclosure
Although the disclosed subject matter will be described in terms of certain embodiments/examples, other embodiments/examples, including embodiments/examples that do not provide all of the benefits and features set forth herein, are also within the scope of the present disclosure.
This application claims priority to U.S. Provisional Application No. 62/614,232, filed on Jan. 5, 2018, and U.S. Provisional Application No. 62/710,498, filed on Feb. 16, 2018, the disclosures of which are incorporated by reference.
This invention was made with government support under contract no. IIP1660177 awarded by the National Science Foundation. The government has certain rights in the invention.
Filing Document | Filing Date | Country | Kind |
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PCT/US2019/012576 | 1/7/2019 | WO | 00 |
Number | Date | Country | |
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62614232 | Jan 2018 | US | |
62710498 | Feb 2018 | US |