Nanotechnology generally refers to a field of technology that controls matter on an atomic or molecular scale (typically 100 nanometers or smaller). Nanotechnology is used for the fabrication of devices or materials that lie within the scale.
Nanotechnology has been recently developed rapidly for various applications in a number of technology fields. Examples of such fields include, but are not limited to, applied physics, materials science, interface and colloid science, device physics, molecular chemistry, self-replicating machines and robotics, chemical engineering, mechanical engineering, biological engineering, and electrical engineering. In certain instances, a structure or material made by nanotechnology can be used in a number of different technology fields.
An aspect by way of non-limiting example includes a method of making a membrane structure. The method includes: providing a substrate and forming a first layer over the substrate. The first layer is formed of a metallic material. The method also includes providing a second layer of oxide particles over the first layer; and pressing the second layer against the first layer such that at least a portion of the first layer is inserted into gaps between the oxide particles.
Another aspect by way of non-limiting example includes an apparatus that includes a membrane comprising pores formed in a first surface thereof, wherein the pores are distributed in the first surface. The membrane is formed of a metallic material. The membrane has a thickness between about 1 nm and about 100 nm. The pores have an average size between about 3 nm and about 500 nm.
Yet another aspect by way of non-limiting example includes a method of catalyzing a water gas shift reaction. The method can include providing the apparatus described above, and contacting the apparatus with a gas and water.
Yet another aspect by way of non-limiting example includes a method of catalyzing an alcohol-aldehyde reaction. The method can include providing the apparatus described above and contacting the apparatus with an alcohol for a period of time sufficient to convert the alcohol to an aldehyde.
Yet another aspect by way of non-limiting example includes an electronic or electrical device that includes the apparatus described above. Yet another aspect by way of non-limiting example includes a method of sensing biomolecules. The method can include providing the apparatus described above and detecting signals from the apparatus. Another aspect by way of non-limiting example relates to electronic or electrical devices that include an apparatus as described above or elsewhere herein.
The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.
The embodiments will be better understood from the Detailed Description and from the appended drawings, which are meant to illustrate and not to limit the embodiments.
In the following detailed description, reference is made to the accompanying drawings, which form a part hereof In the drawings, similar symbols typically identify similar components, unless context dictates otherwise. The illustrative embodiments described in the detailed description, drawings, and claims are not meant to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented here.
The following detailed description is directed to certain specific embodiments. However, the embodiments can be varied in a multitude of different ways. As will be apparent from the following description, the embodiments may be implemented in or associated with a variety of devices and methods.
In one aspect, a method of making a porous membrane or porous membrane structure is provided. One such method includes forming a first layer with a metallic material over a substrate. The first layer may have a thickness between about 1 nm and several hundred nanometers. Then, a second layer of oxide particles is provided over the first layer. The oxide particles can have an average size between about 10 nm and about 1 μm. The second layer is pressed against the first layer such that at least a portion of the first layer is inserted into gaps between the oxide particles. During this process, the second layer may serve as a mold in forming pores in the first layer.
The porous membrane or membrane structure have various applications. The membrane or membrane structure can be used as a catalyst in, for example, electrochemical reactions, water gas shift reactions, or alcohol-aldehyde reactions. The porous membrane or membrane structure can also be used as a stand-alone electrode or conductive line in various fields. The porous membrane or membrane structure may also form a part of a filter, such as an antibiotic filter. The porous membrane or membrane structure may be used as a component of a magnetic memory device. In other instances, the porous membrane or membrane structure can be used for mass manufacturing of composite materials. A skilled artisan will appreciate that the porous membrane or membrane structure can be used for various other applications.
Referring to
In one embodiment, the substrate 110 may be a silicon substrate. The substrate 110 can also include a naturally-formed silicon oxide (SiO2) layer or film 114 that forms the top surface 111. The substrate may have a thickness between about 1 mm and about 10 mm, optionally between about 1 mm and about 5 mm. The thickness can be, for example, about 2 mm or about 3 mm. Such silicon oxide may be referred to as “native silicon oxide,” and may be formed by exposure of the silicon substrate to air. The silicon oxide layer 114 may have a thickness between about 0.5 nm and about 100 nm, or optionally between about 10 nm and about 20 nm. The thickness of the silicon oxide layer 114 may be, for example, about 3 nm, or about 15 nm. A substantial portion 112 of the substrate 110 under the silicon oxide layer 114 is not converted to silicon oxide, and may be referred to as a silicon portion in the context of this document.
In other embodiments, the substrate may be formed of any other suitable material, such as alumina. In such embodiments, the substrate may include a thin layer deposited or naturally formed on a surface thereof The thin layer may have a thickness between about 0.5 nm and about 100 nm, optionally between about 10 nm and about 20 nm. The thin layer may be formed of a material (for example, silicon oxide) that can be removed by a method different from a method for removing the material of the substrate. In certain embodiments, the substrate may not include a thin layer as described above.
A thin metallic layer 120 can be deposited on the silicon oxide layer 114, as shown in
Oxide particles 130 are provided over the metallic layer 120 such that the oxide particles are closely packed, as shown in
The oxide particles 130 are pressed against the metallic layer 120. In one embodiment, the structure resulting from the step shown in
During this step, the metal or alloy of the metallic layer 120 may be in a molten state or mollified state, and may at least partially fill cavities between the oxide particles 130. Such cavities can also be referred to as gaps or spaces. In addition, at least a portion of remnant organic compounds (e.g., a surfactant, such as citrate) that have been used for depositing the oxide particles 130 may be removed. For instance, the organic compounds may be removed by thermal decomposition while the structure of
The structure resulting from the step described above in connection with
The silicon oxide layer 114 is removed, as shown in
A portion of the resulting metallic porous membrane is shown in
Referring to
A metallic layer 320 can be formed with metallic nanoparticles 322 on the silicon oxide layer 314, as shown in
Optionally, the structure shown in
Oxide particles 330 are provided over the metallic layer 320 such that the oxide particles are closely packed, as shown in
The oxide particles 330 are pressed against the metallic layer 320. The details of this step can be as described above in connection with
The silicon oxide layer 314 is removed. In one embodiment, the silicon oxide layer 314 may be etched by an etchant, such as hydrogen fluoride (HF). In some embodiments, the oxide particles are also removed, thereby leaving a free-standing membrane having pores. The details of this step can be as described above in connection with
Referring to
A metallic layer 420 can be formed on the silicon oxide layer 414. In one embodiment, the metallic layer 420 may be deposited by an atomic layer deposition (ALD) process, as described above in connection with
Oxide particles 430 can be provided over a carrier substrate 450 such that the oxide particles are closely packed, as shown in
The structure shown in
Then, the two structures of
The carrier substrate 450 is removed from the structure. In an embodiment where the carrier substrate 450 is formed of PDMS, it can be lifted off from the oxide particles 430. In other embodiments, the carrier substrate 450 can be etched. Subsequently, the silicon portion 412 of the substrate 410 is removed by, for example, plasma etching. The details of this step can be as described above in connection with
The silicon oxide layer 414 is removed. In one embodiment, the silicon oxide layer 414 may be removed by an etchant, such as hydrogen fluoride (HF). In some embodiments, the oxide particles may also be removed, thereby leaving a free-standing membrane having pores. The details of this step can be as described above in connection with
Methods of making a porous membrane structure according to one or more embodiments will be described below. In one embodiment, a structure can be prepared to include a substrate (which includes, for example, a silicon portion and a silicon oxide layer, a metallic layer, and oxide particles, as described above in connection with
Parts of the silicon portion of the substrate are removed by, for example, plasma etching, such that one or more openings” are formed through the silicon portion of the substrate. The openings may be uniformly or semi-uniformly distributed on a surface of the substrate. The openings may have an average diameter of several to several hundred microns, for example, about 50 μm to about 1 mm, or optionally about 200 μm to about 500 μm. The average diameter of the openings may be, for example, about 200 μm or about 500 μm. A skilled artisan will, however, appreciate that the size and shape of the openings can vary widely, depending on the application of the porous membrane structure. As a result, portions of the silicon oxide layer are exposed through the openings. This step can be carried out using any suitable lithographic process.
The exposed portions of the silicon oxide layer are removed, thereby exposing portions of the metallic layer. The portions of the silicon oxide layer may be etched by an etchant, such as hydrogen fluoride (HF). In some embodiments, the oxide particles may also be removed, thereby leaving the porous membrane structure shown in
In the illustrated embodiment, the structure 500 includes a substrate 510 (which includes a silicon portion 512 and a silicon oxide layer 514) and a metallic layer 520.
The substrate 510 including the openings can serve as a support structure of the porous membrane 520. This configuration provides structural stability in various applications, as will be described below. Further, the configuration allows the porous membrane 520 to be easily handled in such applications.
Referring to
Subsequently, the oxide particles 630 are pressed against the metallic layer 620. The details of this step can be as described above in connection with
Next, a support substrate 660 is attached (by, for example, contacting and heating) to the structure 601 such that a surface of the support substrate 660 faces and contacts the oxide particles 630 and/or the metallic layer 620, as shown in
Subsequently, the silicon portion 612 of the substrate 610 is removed by, for example, plasma etching. The details of this step can be as described above in connection with
The porous membranes or membrane structures described above can have various applications. Referring to
The porous membrane 710 can be formed by any method described above in connection with
In one embodiment, the porous membrane structure 700 can be used in an electrochemical reaction. The electrochemical reaction can be used to amplify signals for sensing biomolecules, such as DNA, RNA, protein, or the like. The porous membrane 710 serves as a catalyst in the reaction while the electrode 720 serves as an anode or cathode in the reaction, as described below.
In another embodiment, the porous membrane structure 700 can be used in a water gas shift (WGS) reaction. In such an embodiment, the porous membrane structure described above in connection with
In yet another embodiment, the porous membrane structure 700 can be used in an alcohol-aldehyde reaction. In such an embodiment, the porous membrane structure described above in connection with
In yet another embodiment, a porous membrane formed of gold can be made by the methods described above. In such an embodiment, biomolecules may be attached onto the membrane. The porous membrane may be used in detecting molecules by enhancing the fluorescence of a dye molecule. Details about fluorescence enhancement is disclosed in Ganesh et al., “Enhanced Fluorescence Emission From Quantum Dots On a Photonic Crystal Surface,” Nature Nanotechnology, 2, 515-520 (2007), the disclosure of which is incorporated here by reference.
In some embodiments, the porous membrane described above can be used as a free-standing electrode, as shown in
In other embodiments, the porous membrane described above can be used as a conductor in an electronic or electrical device. In such embodiments, the metallic layer used for the making the porous membrane is formed of electrically conductive material, such as, but not limited to, gold, silver, or copper, or an alloy thereof, for example. The porous membrane can be made very thin and narrow such that it is substantially transparent while providing desired electrical conductivity. In one embodiment, the porous membrane can have a pore size greater than about 100 nm and a thickness of less than about 50 nm. Such porous membranes can be used on a vehicle window as, for example, an antenna component.
In certain embodiments, the porous membrane described above can be used as a component of a filter. Referring to
In another embodiment, the porous membrane described above can be used as a component of a memory device, for example, a magnetic memory device. In such an embodiment, the porous membrane may be formed of an Ru—Pt alloy, or the like for example. A skilled artisan will appreciate that any suitable materials can be used for making the porous membrane for use as a magnetic memory component.
In other embodiments, the porous membrane described above can be used for making a noble metal-metal oxide composite. As described above with respect to
In at least some of the aforesaid embodiments, any element used in an embodiment can interchangeably be used in another embodiment unless such a replacement is not feasible. It will be appreciated that the steps of the methods described above can be combined, divided, or omitted or that additional steps can be added. It will also be appreciated by those skilled in the art that various other omissions, additions and modifications may be made to the methods and structures described above without departing from the scope of the embodiments.
For purposes of this disclosure, certain aspects, advantages, and novel features of the embodiments are described herein. It is to be understood that not necessarily all such advantages may be achieved in accordance with any particular embodiment. Thus, for example, those skilled in the art will recognize that some embodiments may be embodied or carried out in a manner that achieves one advantage or group of advantages as taught herein without necessarily achieving other advantages as may be taught or suggested herein.
The herein described subject matter sometimes illustrates different components contained within, or connected with, different other components. It is to be understood that such depicted architectures are merely illustrative, and that in fact many other architectures can be implemented which achieve the same functionality. In a conceptual sense, any arrangement of components to achieve the same functionality is effectively “associated” such that the desired functionality is achieved. Hence, any two components herein combined to achieve a particular functionality can be seen as “associated with” each other such that the desired functionality is achieved, irrespective of architectures or intermedial components. Likewise, any two components so associated can also be viewed as being “operably connected,” or “operably coupled,” to each other to achieve the desired functionality, and any two components capable of being so associated can also be viewed as being “operably couplable,” to each other to achieve the desired functionality. Specific examples of operably couplable include but are not limited to physically mateable and/or physically interacting components and/or wirelessly interactable and/or wirelessly interacting components and/or logically interacting and/or logically interactable components.
With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. The various singular/plural permutations may be expressly set forth herein for sake of clarity.
It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases “at least one” and “one or more” to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles “a” or “an” limits any particular claim containing such introduced claim recitation to embodiments containing only one such recitation, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an” (e.g., “a” and/or “an” should typically be interpreted to mean “at least one” or “one or more”); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of “two recitations,” without other modifiers, typically means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogous to “at least one of A, B, and C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, and C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). In those instances where a convention analogous to “at least one of A, B, or C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, or C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). It will be further understood by those within the art that virtually any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase “A or B” will be understood to include the possibilities of “A” or “B” or “A and B.”
While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.