US20140190979A1

US20140190979A1 - Container for the transport and transfer of nanomaterials

Info

Publication number: US20140190979A1
Application number: US13/736,992
Authority: US
Inventors: Yijing Yin Stehle; Xuesong Li; Yu-Ming Lin; Chun-Yung Sung
Original assignee: Bluestone Global Technology Ltd
Current assignee: BLUESTONE TECHNOLOGIES (CAYMAN) Ltd
Priority date: 2013-01-09
Filing date: 2013-01-09
Publication date: 2014-07-10

Abstract

Aspects of the invention are directed to a container comprising a tub, a basket, and a lid. The tub is adapted to hold a liquid and comprises a bottom and a tub sidewall having an upper rim defining an opening in the tub. The basket is disposed on the bottom of the tub and comprises a base and a basket sidewall. The base defines a perimeter, and the basket sidewall runs along at least a portion of this perimeter. The lid contacts the upper rim and comprises a filler piece. The filler piece occupies a volume inside the tub between the base and a plane defined by the upper rim. The container is adapted to hold a sensitive film stack without damage or degradation to the film stack. The container is further adapted to facilitate the easy transfer of the film stack to a new substrate.

Description

FIELD OF THE INVENTION

The present invention relates generally to containers, and, more particularly, to containers for use in handling sensitive materials such as nanomaterials.

BACKGROUND OF THE INVENTION

Nanomaterials are presently the target of intense study because of their many interesting and useful mechanical, optical, and electrical properties. Graphene, for example, can exhibit very high electron- and hole-mobilities and, as a result, may allow graphene-based electronic devices to display extremely high switching speeds. Moreover, because graphene is planar, it is compatible with many well-developed semiconductor processing techniques. Graphene may also be used as an electrode material in energy storage devices, as a membrane material in electromechanical systems, as a pressure sensor, as a detector for chemical or biological molecules or cells, and in a multiplicity of other such technical applications.
Presently, high quality and large area graphene can be formed by chemical vapor deposition (CVD). Such CVD processes typically involve exposing a copper foil substrate to hydrogen and methane in a CVD tube furnace reactor. Once so formed, the graphene can be transferred from the copper foil deposition substrate to another substrate for use in whatever application is of interest. That said, because of the delicate nature of graphene, such a “substrate transfer” process must be handled very carefully to avoid film damage and degradation. In fact, the transfer of the graphene from its copper deposition substrate to a new substrate is typically a multi-step process. In one methodology, for example, substrate transfer is initiated by depositing a thin polymer coating on a graphene-copper film stack and then floating the resulting polymer-graphene-copper film stack on a bath of a liquid copper etchant to remove the copper foil deposition substrate. The resultant polymer-graphene film stack is then cleaned several times by sequentially floating the film stack on several baths of deionized water. After being sufficiently cleaned, a new substrate is immersed in a water bath under the floating polymer-graphene film stack and lifted upward and out of the water bath so as to place the film stack on top of the new substrate. The polymer layer is then stripped by rinsing the polymer-graphene-substrate film stack with an appropriate etchant. After some further cleaning and drying, the desired graphene-substrate film stack is finally achieved.
Because of the above-described nature of the substrate transfer process for graphene, a recipient who buys graphene from a graphene manufacturer with the graphene still on its original copper deposition substrate must have a certain amount of expertise in wet chemical processing in order to transfer the received graphene to whatever substrate that recipient wishes to utilize. Many recipients do not have this kind of expertise, nor do they necessarily have the required wet chemical processing infrastructure. The alternative, that is, for the recipient to send its substrate to the graphene manufacturer and have the manufacturer perform the substrate transfer process at the manufacturer's site, is also not particularly attractive. Shipping substrates back and forth is burdensome and time consuming. Moreover, because of the proprietary nature of many applications, these recipients are not interested in exposing their substrates to inspection offsite.
For the foregoing reasons, there is a need for apparatus that allow a nanomaterial such as CVD graphene to be shipped to a recipient site without damage or degradation, and, once at the recipient site, facilitate the recipient in transferring that nanomaterial to whatever new substrate the recipient desires without requiring that the recipient perform numerous or complex processing steps.

SUMMARY OF THE INVENTION

Embodiments of the present invention address the above-identified needs by providing a container that both serves to protect a film stack containing a nanomaterial during transport, and to ease the transfer of the nanomaterial in the film stack to a new substrate after the nanomaterial reaches its destination.
Aspects of the invention are directed to a container comprising a tub, a basket, and a lid. The tub is adapted to hold a liquid and comprises a bottom and a tub sidewall having an upper rim defining an opening in the tub. The basket, in turn, is disposed on the bottom of the tub and comprises a base and a basket sidewall. The base defines a perimeter, and the basket sidewall runs along at least a portion of this perimeter. The lid contacts the upper rim and comprises a filler piece. The filler piece occupies a volume inside the tub between the base and a plane defined by the upper rim.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings where:

FIG. 1 shows a perspective view of a container enclosing a film stack, in accordance with an illustrative embodiment of the invention;

FIG. 2 shows a perspective view of the FIG. 1 container and film stack with the lid removed;

FIG. 3 shows an exploded perspective view of the FIG. 1 container and film stack;

FIG. 4 shows a perspective view the FIG. 1 film stack on the basket of the FIG. 1 container;

FIG. 5 shows a sectional view of the FIG. 1 film stack on the basket of the FIG. 1 container;

FIG. 6 shows a perspective view of one of the tabs of the basket of the FIG. 1 container;

FIG. 7 shows a perspective view of the lid of the FIG. 1 container;

FIG. 8 shows a sectional view of the lower surface of the lid of the FIG. 1 container;

FIG. 9 shows another exploded perspective view of the FIG. 1 container and film stack;

FIG. 10 shows a sectional view of the FIG. 1 container and film stack with the container in its closed state;

FIG. 11 shows a magnified sectional view of a lower corner of the FIG. 1 container and film stack with the container in its closed state;

FIG. 12 shows a magnified sectional view of a lower central region of the FIG. 1 container and film stack with the container in its closed state;

FIG. 13 shows a perspective view of the FIG. 1 container and film stack with the lid, cover sheet, basket, and film stack removed from the tub, and the tub being filled with water;

FIG. 14 shows a partially cutaway perspective view of the FIG. 1 film stack and the basket of the FIG. 1 container being placed into the water-filled tub of the FIG. 1 container;

FIG. 15 shows a sectional view of the FIG. 1 film stack rising to float on water in the tub of the FIG. 1 container;

FIG. 16 shows a magnified sectional view of the FIG. 1 film stack floating on water in the tub of the FIG. 1 container;

FIG. 17 shows a perspective view of a recipient's substrate being inserted into the basket of the FIG. 1 container below the floating FIG. 1 film stack;

FIG. 18 shows a perspective view of the recipient's substrate resting on the basket of the FIG. 1 container below the floating FIG. 1 film stack;

FIG. 19 shows a perspective view of the basket of the FIG. 1 container being removed from the tub of the FIG. 1 container such that the FIG. 1 film stack becomes positioned onto the recipient's substrate;

FIG. 20 shows a sectional view of the FIG. 1 film stack disposed on the recipient's substrate on the basket of the FIG. 1 container; and

FIG. 21 shows a side elevational view of the FIG. 1 film stack disposed on the recipient's substrate with the protective film being removed by acetone.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will be described with reference to illustrative embodiments. For this reason, numerous modifications can be made to these embodiments and the results will still come within the scope of the invention. No limitations with respect to the specific embodiments described herein are intended or should be inferred.
FIGS. 1-8 show various aspects of a container 100 enclosing a nanomaterial-containing film stack 200, in accordance with an illustrative embodiment of the invention. The container 100 can be conceptually separated into four base elements: a tub 105, a basket 110, a cover sheet 115, and a lid 120. When the container 100 is in its closed state, these four base elements nest to form a unified structure in which the film stack 200 can be shipped to a remote recipient without damage or degradation. Once at the recipient's site, the container 100 is adapted to come apart to form a “kit” that facilitates the recipient in transferring the nanomaterial from the film stack 200 to whatever new substrate the recipient desires. The illustrative container 100 thereby serves at least two separate functions: 1) safe transport of the film stack 200; and 2) eased transfer of the nanomaterial in the film stack 200 to a new substrate.
FIG. 1 shows a perspective view of the container 100 and the film stack 200 while the container 100 is in its closed state. In addition, FIG. 2 shows a perspective view of the container 100 and the film stack 200 with the lid 120 removed, and FIG. 3 shows an exploded perspective view of the container 100 and the film stack 200. In the present illustrative embodiment, the tub 105 comprises a bottom 125 that is substantially square in shape. A tub sidewall 130 is attached to the bottom 125 and forms a watertight volume therewith, which allows the tub 105 to hold a liquid (e.g., water) without leakage. An upper rim 135 at the top of the tub sidewall 130 defines an opening 140 in the tub 105. The tub 105 is preferably transparent. The tub 105 may be formed, for example, from a transparent thermoplastic polymer such as polycarbonate, polyvinyl chloride, polyamide, polypropylene, and a multiplicity of other materials.
The basket 110 is perhaps the most complex element of the container 100 because it comes into direct contact with the film stack 200 during transport and also serves several functions during the subsequent substrate transfer process. In a manner similar to the tub 105, the basket 110 includes a base 145 that is in the shape of a square. Nevertheless, the base 145 has dimensions (i.e., width and length) somewhat smaller than the bottom 125 of the tub 105 so that the basket 110 can rest on the bottom 125 of the tub 105 when the container 100 is in its closed state. A basket sidewall 150 runs along three of the four sides of the base 145, leaving one side of the basket 110 without the sidewall and open. In so doing, the basket sidewall 150 can be described as running along only a portion of the perimeter of the base 145. The basket sidewall 150, moreover, defines a plurality of apertures 155 therein. Like the tub 105, the basket sidewall 150 may comprise a clear thermoplastic polymer. The base 145 of the basket 110, in contrast, preferably comprises a fabric comprising, for example, polyester thread. The dissimilar materials of the plastic basket sidewall 150 and the fabric base 145 may be attached to one another by, for example, an adhesive strip (not specifically shown). FIG. 4 shows a perspective view of the basket 110 and the film stack 200 with the film stack 200 sitting on the base 145 of the basket 110, as it would be during transport. FIG. 5 shows a sectional view of the film stack 200 resting in this position.
In addition to the base 145 and the basket sidewall 150, the basket 110 also includes two tabs 160. FIG. 6 shows a perspective view of one of these two tabs 160. Each of the tabs 160 is rotatably coupled to a respective side of the basket sidewall 150 via a respective screw 165. Each of the tabs 160 is thereby able to be rotated so that it aligns with its respective sidewall portion or projects outward from its respective sidewall portion. In this manner, the tabs 160 allow the basket 110 to be suspended from the upper rim 135 of the tub 105, which, as will be detailed below, is a useful function during substrate transfer.
The cover sheet 115 in the present illustrative embodiment is merely a sheet of fabric that acts to protect the upper surface of the film stack 200. It may, as a result, be formed of the same material as the base 145 of the basket 110 (e.g., a fabric formed of polyester thread).
Lastly, the lid 120 comprises a cover 170 and a filler piece 175, and may be formed from the same material as the tub 105 (e.g., a transparent thermoplastic polymer). When the container 100 is closed, the cover 170 is adapted to contact the upper rim 135 of the tub 105 and thereby act to close the opening 140 in the tub 105. So positioned, the cover 170 may be removably fixated to the tub 105 by one of several temporary fixation means such as a relatively weak adhesive (e.g., rubber cement), elastic straps (e.g., rubber bands), or external wrapping (e.g., cellophane) (none of which is specifically shown in the figures). The filler piece 175 of the lid 120 defines a hollow square block that protrudes downward from the cover 170. The filler piece 175 is dimensioned so that, when the tub 105 is closed by the lid 120 with the basket 110 in place, the filler piece 175 occupies most of the volume inside the tub 105 between the base 145 of the basket 110 and a plane 180 defined by the upper rim 135 of the tub 105 (shown in FIG. 3). That is, the filler piece 175 has a width and length slightly smaller than the base 145 of the basket 110, while having a height slightly smaller than the distance between the base 145 and the plane 180. In this position, a lower surface 185 of the filler piece 175 faces the bottom 125 of the tub 105. FIG. 7 shows a perspective view of the lid 120 alone with the lower surface 185 clearly visible, while FIG. 8 shows a sectional view of the lower surface 185 of the lid 120. In the present embodiment, the lower surface 185 is not entirely flat but has beveled edges 190 that cause the lower surface 185 to appear somewhat recessed or concave when viewed looking up from the bottom 125 of the tub 105.
The above-described container 100 is suitable for handling many different types of nanomaterials with different morphologies (e.g., films, particles, rods, pills, cages, fibers, shells). Nevertheless, for purposes of describing aspects of the invention, the film stack 200 is assumed to comprise one or more layers of graphene 205 coated by a protective coating 210 of poly(methylmethacrylate) (PMMA), a type of transparent thermoplastic polymer easily stripped by acetone ((CH₃)₂CO). These constituent members of the film stack 200 are explicitly labeled in the magnified sectional view in FIG. 5. Graphene, as that term is used herein, refers to a planar sheet of sp²-bonded carbon atoms that are densely packed in a honeycomb crystal lattice. High quality and large-area graphene films (both single layer and multi-layer) can be synthesized by CVD on metal substrates such as copper foil. U.S. Patent Publication No. 2011/0091647, to Colombo et al. and entitled “Graphene Synthesis by Chemical Vapor Deposition,” hereby incorporated by reference herein, for example, teaches the CVD of graphene on metal substrates using hydrogen (H₂) and methane (CH₄) in an otherwise largely conventional CVD tube furnace reactor. A copper foil substrate is loaded into the CVD tube furnace and hydrogen gas is introduced at a rate between 1 to 100 standard cubic centimeters per minute (sccm) while heating the substrate to a temperature between 400 degrees Celsius (° C.) and 1,400° C. These conditions are maintained for a duration of time between 0.1 to 60 minutes. Next methane is introduced into the CVD tube furnace at a flow rate between 1 to 5,000 sccm at between 10 mTorr to 780 Torr of pressure while reducing the flow rate of hydrogen gas to less than 10 sccm. Graphene is synthesized on the copper foil substrate over a period of time between 0.001 to 10 minutes following the introduction of the methane.
Once synthesized on a copper foil, the one or more layers of graphene 205 can be coated by the PMMA protective coating 210 utilizing conventional spray coating or spin coating techniques. The copper foil can then be selectively removed by floating the polymer-graphene-copper film stack with the PMMA facing up on a bath of copper etchant comprising, for example, ferric chloride (FeCl₃), hydrochloric acid (HCl), and water. With the copper foil removed, the polymer-graphene film stack 200 can be washed by floating it on one or more baths of deionized water (H₂O).
The resultant film stack 200 (i.e., PMMA-graphene) is then in condition for placement in the container 100 and shipment to its intended location. FIGS. 9-12 show various aspects of the container 100 and the film stack 200 during such transport. More particularly, FIG. 9 shows an exploded perspective view of the container 100 and the film stack 200, while FIG. 10 shows a sectional view of the container 100 and the film stack 200 with the container 100 in its closed state. In addition, FIGS. 11 and 12 show magnified sectional views of a lower corner region and a lower central region, respectively, of the film stack 200 and the container 100 in its closed state. In preparation for transport, the film stack 200 is first placed on the base 145 of the basket 110 with the PMMA protective coating 210 facing up, and the basket 110 is then placed on the bottom 125 of the tub 105. The cover sheet 115 is then placed on the film stack 200 and the base 145, and finally, the lid 120 is removably attached to the upper rim 135 of the tub 105 so as to close the container 100. Configured in this manner, the filler piece 175 of the lid 120 presses down on the cover sheet 115 which, in turn, presses the base 145 of the basket 110 against the bottom 125 of the tub 105. At the same time, the film stack 200 is firmly sandwiched between the cover sheet 115 and the base 145 of the basket 110, where it is held immobile. Advantageously, the slightly recessed shape of the lower surface 185 of the filler piece 175 causes the filler piece 175 to place more of its pressing force on the peripheries of the cover sheet 115 and the base 145 of the basket 110, while placing less pressure on the center of the cover sheet 115 and the base 145 where the film stack 200 is located. Although the film stack 200 is still firmly held in place, the chance of mechanical damage to the film stack 200 caused by its enclosure in the container 100 is thereby reduced.
Once safely received by the recipient, the container 100 is then able to serve its second function, that is, to serve as a kit for the easy transfer of the enclosed film stack 200 to a substrate of the recipient's choosing (hereinafter, the “recipient's substrate” 300). FIGS. 13-21 go on to show aspects of various intermediate steps of this transfer process. In describing this processing, the film stack 200 continues to be assumed for illustrative purposes to be the graphene 205 coated with the PMMA protective coating 210. The graphene 205 faces the base 145 of the basket 110, and the PMMA protective coating 210 faces upward.
The initial step of the substrate transfer process has the recipient remove the lid 120 from the tub 105, and, with the lid 120 no longer in place, remove the cover sheet 115 and the basket 110 from the tub 105. The recipient is then instructed to deploy the two tabs 160 on the basket 110 so that the tabs 160 extend outward from the basket sidewall 150. The recipient is further instructed to fill the tub 105 with deionized water 195. The performance of these steps is shown by the perspective view of FIG. 13.
Next, the recipient is instructed to suspend the basket 110 from the upper rim 135 of the tub 105 (using the deployed tabs 160), as shown in in the partially cutaway perspective view in FIG. 14. This, in turn, causes the PMMA-graphene film stack 200 to float off of the base 145 of the basket 110 to the surface of the water 195. Such a condition is shown in FIGS. 15 and 16, where FIG. 15 shows a sectional view of the film stack 200 rising to float on the water 195 of the tub 105, and FIG. 16 shows a magnified sectional view of the film stack 200 floating on the water 195 in the tub 105.
The recipient is then further instructed to place the recipient's substrate 300 into the basket 110 so that the recipient's substrate 300, which does not float, ultimately falls onto the base 145 of the basket 110 below the floating PMMA-graphene film stack 200. This insertion is facilitated by the “missing” sidewall portion of the basket 110. FIG. 17 shows a perspective view of the insertion of the recipient's substrate 300 into the basket 110 below the floating film stack 200. FIG. 18, in turn, shows a perspective view of the recipient's substrate 300 positioned in the basket 110 below the floating film stack 200.
With the recipient's substrate 300 positioned in the basket 110 below the floating PMMA-graphene film stack 200, the recipient is then instructed to lift the basket 110 from the tub 105 so that the film stack 200 becomes positioned onto the recipient's substrate 300. Venting of the water 195 while the basket 110 is being lifted from the tub 105 is facilitated by the apertures 155 in the basket sidewall 150. The raising of the basket 110 in this manner is illustrated in the perspective view in FIG. 19. The resultant placement of the film stack 200 on the recipient's substrate 300 is shown in the sectional view in FIG. 20.
Finally, the recipient is instructed to remove the recipient's substrate 300 (on which is deposited the PMMA-graphene film stack 200) from the basket 110 and to strip off the PMMA protective coating 210 with an appropriate solvent. PMMA is, for example, readily removed by acetone. FIG. 21 shows a side elevational view of this processing step. In so doing, the substrate transfer is completed and the recipient is left with the bare graphene 205 on the recipient's substrate 300.
In this manner, the container 100, when combined with an appropriately configured nanomaterial-containing film stack like the film stack 200, serves dual functions. When in its closed state, the container 100 forms a unified structure in which a sensitive film stack can be shipped without degradation or damage. Once at the recipient's site, the container 100 comes apart to form a kit that facilitates the recipient in transferring the nanomaterial to whatever new substrate the recipient desires. The recipient needs have no special expertise in the transfer processing but, instead, needs only follow simple instructions and utilize readily available chemicals such as deionized water and acetone. There is no need for the recipient to send its substrate to the graphene manufacturer's site. Shipping times are saved and, perhaps more importantly, the recipient's often-proprietary substrate is not open to inspection offsite.
In closing, it should again be emphasized that the above-described embodiments of the invention are intended to be illustrative only. Other embodiments can use different types and arrangements of elements for implementing the described functionality. As just one example, while the particular embodiment of the container described above has a largely square footprint, this shape is merely illustrative and any other suitable shape (e.g., rectangular, circular, elliptical, hexagonal, etc.) would also fall within the scope of the invention. In such a manner, a container in accordance with aspects of the invention may easily be adapted to accommodate different film stack shapes and recipient substrate shapes. These numerous alternative embodiments within the scope of the appended claims will be apparent to one skilled in the art.
Moreover, all the features disclosed herein may be replaced by alternative features serving the same, equivalent, or similar purposes, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

Claims

What is claimed is:

1. A container comprising:

(a) a tub, the tub adapted to hold a liquid and comprising a bottom and a tub sidewall having an upper rim defining an opening in the tub;

(b) a basket, the basket disposed on the bottom and comprising:

(i) a base, the base defining a perimeter; and

(ii) a basket sidewall, the basket sidewall running along at least a portion of the perimeter; and

(c) a lid, the lid contacting the upper rim and comprising a filler piece, the filler piece occupying a volume inside the tub between the base and a plane defined by the upper rim.

2. The container of claim 1, wherein the base comprises a fabric.

3. The container of claim 1, wherein the lid covers the opening in the tub.

4. The container of claim 1, wherein the filler piece defines a lower surface, the lower surface disposed inside the tub and facing the bottom.

5. The container of claim 4, wherein the lower surface defines a beveled edge.

6. The container of claim 1, wherein the basket sidewall runs along only a portion of the perimeter.

7. The container of claim 1, where the base describes four edges and the basket sidewall runs along only three of the four edges.

8. The container of claim 1, wherein the basket sidewall defines an aperture therein.

9. The container of claim 1, wherein the basket is adapted such that it can be suspended in the tub from the tub sidewall.

10. The container of claim 1, wherein the basket further comprises a tab, the tab adapted to be positioned such that it extends outwardly from the basket sidewall.

11. The container of claim 1, wherein the container encloses a film stack, the film stack disposed between the base and the filler piece.

12. The container of claim 11, wherein the film stack comprises a nanomaterial.

13. The container of claim 12, wherein the nanomaterial comprises graphene.

14. The container of claim 12, wherein the nanomaterial is at least partially covered by a polymer coating.

15. The container of claim 14, wherein the polymer coating is operative to be stripped by acetone.

16. The container of claim 14, wherein the polymer coating comprises poly(methyl methacrylate).

17. The container of claim 11, wherein the film stack floats when placed in the liquid.

18. The container of claim 11, further comprising a cover sheet, the cover sheet disposed between the film stack and the filler piece.

19. The container of claim 18, wherein the cover sheet comprises a fabric.

20. The container of claim 11, wherein the film stack is substantially held immobile against the base.