WO2010126627A2 - Processes for the preparation of carbon nanotubes layers coated on a flexible substrate and carbon nanotubes fibers made therefrom - Google Patents

Abstract

A method of making a carbon nanotube fiber by combining a carbon nanotube and a non-surfactant organic solvent to form carbon nanotubes dispersed in the nanotube solution. A substrate is contacted with the nanotube solution to form a nanotube coated substrate and the nanotube coated substrate may be recoated numerous times to apply additional nanotube coatings to the substrate. The nanotube coated substrate is contacted with an acid solution, aqueous solution and an alcohol source and dried. The nanotube fiber is drawn from the nanotube coated substrate. In some instances, the nanotube fiber is twisted as it is drawn. The carbon nanotube may be a single-walled nanotube, double-walled nanotube, multi-walled nanotube, or a mixture thereof with less than 100 Ohm per sq and/or about 90% transmittance or less than 90% transmittance at about 400-700nm wavelength.

Description

PROCESSES FOR THE PREPARATION OF CARBON NANOTUBES LAYERS COATED ON A FLEXIBLE SUBSTRATE AND CARBON NANOTUBES FIBERS

MADE THEREFROM

Technical Field of the Invention The present invention relates in general to the field of making carbon nanotubes and more specifically, compositions and methods of making fibers from single-walled nanotubes, double- walled nanotubes, multi-walled nanotubes, coating compositions, and coating preparation with no use of surfactant. Methods of coating comprised single-walled nanotubes, double-walled nanotubes, or multi-walled nanotubes, or mixture thereof onto substrates. Background Art

Without limiting the scope of the invention, its background is described in connection with making carbon nanotubes. More specifically compositions and methods of making fibers from single-walled nanotubes, double-walled nanotubes, or multi-walled nanotubes.

Generally, carbon nanotubes (CNTs) are allotropes of carbon with a nanostructure that can have an extremely high length-to-diameter ratio. Carbon nanotubes are members of the fullerene structural family and their name is derived from their size. Since the diameter of a nanotube is in the order of a few nanometers, while they can be up to several millimeters in length and may be categorized as single-walled nanotubes (SWNTs) and multi-walled nanotubes (MWNTs).

Generally, carbon nanotubes are one of the strongest and stiffest materials, in terms of tensile strength and elastic modulus. This strength results from the covalent sp² bonds formed between the individual carbon atoms. These cylindrical carbon molecules have novel properties that make them potentially useful in many applications in nanotechnology, electronics, optics, and other fields of material science, as well as, potential use in architectural fields. They exhibit extraordinary strength and unique electrical properties, and are efficient conductors of heat. Their final usage, however, may be limited by their potential toxicity.

For example, it has been shown that carbon nanotubes can cross the membrane barriers and suggests that if raw materials reach the organs they can induce harmful effects as inflammation, epithelioid granulomas (microscopic nodules), fibrosis, and biochemical/toxicological changes in the lungs. Disclosure of the Invention

The present invention provides compositions and methods of manufacturing a carbon nanotube by combining a carbon nanotube and a non-surfactant organic solvent to form a nanotube solution; dispersing the carbon nanotubes in the nanotube solution; contacting a substrate with the nanotube solution to form a nanotube coated substrate; optionally re-contacting the nanotube coated substrate to apply additional coatings to the nanotube coated substrate; and drying the nanotube coated substrate.

The present invention provides compositions and methods of coating carbon nanotubes on a substrate by combining a carbon nanotube and a non-surfactant organic solvent to form a nanotube solution; dispersing the carbon nanotubes in the nanotube solution; contacting a substrate with the nanotube solution to form a nanotube coated substrate; optionally re- contacting the nanotube coated substrate to apply additional coatings to the nanotube coated substrate; and drying the nanotube coated substrate.

The present invention provides a novel, versatile and robust process for the production of CNT coated film/substrate from single-walled nanotubes (SWNTs), double-walled nanotubes

(DWNTs), or multi-walled nanotubes (MWNTs), or mixture thereof. For example, the present invention provides flexible transparent conductor with between 30 and 150 Ω/sq with 80-100% transmittance in the wavelength range of 400-700nm on a flexible substrate. One specific example had 100 Ω/sq with 90% transmittance in the wavelength range of 400-700nm on a flexible substrate.

The present invention provides a novel, versatile, and robust process for the production of coatings from single -walled nanotubes (SWNTs), double -walled nanotubes (DWNTs), or multi- walled nanotubes (MWNTs), or mixture thereof including coating of them on a plastic substrate or film. The present invention provides a method of producing tailored substrates having specific desired physical properties.

The present invention provides a method to coat uniform CNTs layer on a substrate via dipping using a sonication. The present invention provides coating compositions and methods of making a carbon nanotube coating by combining a carbon nanotube and a non-surfactant organic solvent to form a nanotube solution that is coated onto a substrate. The carbon nanotube is dispersed in the nanotube solution by a sonication and the substrate is contacted with the nanotube solution to form a nanotube coated substrate, preferably while the solution is being sonicated. The nanotube coated substrate may be recoated numerous times to apply additional nanotube coats to the nanotube coated substrate. The carbon nanotube is a single-walled nanotube, double-walled nanotube, multi-walled nanotube or a mixture thereof and has less than 200 Ohm per sq and/or about 90% transmittance at about 400-700nm wavelength.

The present invention provides a novel, versatile, and robust process for the production of fibers from single-walled nanotubes (SWNTs), double-walled nanotubes (DWNTs), or multi-walled nanotubes (MWNTs), or mixture thereof including testing of mechanical and electrical properties of various fibers to be prepared by the process. The present invention provides a method of producing tailored fibers having specific desired physical properties.

The present invention provides a method to coat uniform CNT layer on a substrate via dipping or other methods and provides methods to process continuous CNT fibers. The present invention provides a method of producing CNTs having a desired mechanical property or a property range. In addition the present invention provides a method to prepare materials or fabrics using the long fibers to be used for various composites, e.g., ceramic, metal, polymer, and/or hybrid composites. The present invention provides compositions and methods of making a carbon nanotube fiber by combining a carbon nanotube and a non-surfactant organic solvent to form a nanotube solution. The carbon nanotube is dispersed in the nanotube solution. A substrate is contacted with the nanotube solution to form a nanotube coated substrate. The nanotube coated substrate may be recoated numerous times to apply additional nanotube coats to the nanotube coated substrate. The nanotube coated substrate is contacted with an acid solution followed by an aqueous solution and an alcohol source. The nanotube coated substrate is dried and the nanotube fibers are drawn from the nanotube coated substrate. In some instances the nanotube fibers are twisted as they are drawn. The carbon nanotube is a single-walled nanotube, double-walled nanotube, multi-walled nanotube or a mixture thereof and has less than 100 Ohm per sq and/or about 90% transmittance at about 400-700nm wavelength.

Description of the Drawings

For a more complete understanding of the features and advantages of the present invention, reference is now made to a detailed description of the invention along with the accompanying figures and in which: FIGURE 1 is an image of a photograph of transparent and conductive purified HiP co SWNT on flexible PEN substrate. FIGURE 2 is a plot of the flexibility of a SWNT/PET sample and an ITO/PET sample with two probe resistance.

FIGURES 3 A and 3B are chemical structure schematics of PEN and PET, respectively.

FIGURES 4A-4D are AFM images where FIGURE 4A is an image of PET, FIGURE 4B is an image of PEN substrates without coating, FIGURE 4C is an image of PET and FIGURE 4D is an image of PEN substrates after 3 minutes triple time coated with purified HiP co SWNTs.

FIGURES 5A-5C are AFM images of PET treated with UV-ozone where FIGURE 1OA is an image after 2 minutes, FIGURE 1OB is an image after 3 minutes and FIGURE 1OC is an image after 5 minutes. FIGURES 6A-6D are images of CNT coated plastic film and manual Preparation of fiber.

FIGURES 7A and 7B are SEMs of SWNTs coated on plastic film where FIGURE 2a is an image before acid treatment and FIGURE 2b is an image after acid treatment.

FIGURES 8A and 8B are SEMs of SWNT fiber with a 60-70 μm diameter fiber. FIGURES 9A and 9B are SEMs of MWN T fiber with a 50μm Diameter. FIGURES 1OA and 1OB are graphs of the tensile strength and Young's modulus of SWNT fiber prepared from SWNT coated on film.

Description of the Invention

While the making and using of various embodiments of the present invention are discussed in detail below, it should be appreciated that the present invention provides many applicable inventive concepts that can be embodied in a wide variety of specific contexts. The specific embodiments discussed herein are merely illustrative of specific ways to make and use the invention and do not delimit the scope of the invention.

To facilitate the understanding of this invention, a number of terms are defined below. Terms defined herein have meanings as commonly understood by a person of ordinary skill in the areas relevant to the present invention. Terms such as "a", "an" and "the" are not intended to refer to only a singular entity, but include the general class of which a specific example may be used for illustration. The terminology herein is used to describe specific embodiments of the invention, but their usage does not delimit the invention, except as outlined in the claims.

As used herein the term fiber encompasses fibers of various diameters and compositions including twisted and pulled fibers including yarns. The present invention provides a novel, versatile, and robust coating process from single-walled nanotubes (SWNTs), double-walled nanotubes (DWNTs), or multi-walled nanotubes (MWNTs), or mixture thereof on a substrate. For example, the present invention provides flexible transparent conductor with between 0.1 and 100 K Ohms /sq and any specific individual value between, e.g., between 0.4 and 1000 Ohms /sq, 100-1000 Ohms /sq, 0.26 Ohms /sq and so on. In addition, the percentage transmittance range may be between 0-99% and any specific individual value between, e.g., 1-85%, 10-90%, 50%, 0.1-5%, and so on. The wavelength will be between 400-700nm. In addition, the skilled artisan will recognize that the thickness of the substrate may affect these properties and tailor the parameters to produce a desired transparency, and conduction.

The present invention provides a method of making a CNT coating composition and CNT coated plastic substrate having less than 200 Ohm per sq with about 90% transmittance at about 400- 700nm wavelength range to be used as a component for electronic devices. For example, the present invention provides 110 Ω/sq at 88% transmittance using purified single walled nanotubes (SWNTs) coated on a polyethylene naphthalate (PEN) substrate. The present invention also simplifies the overall coating procedure; to reduce the number of steps necessary from five steps (as seen in the prior art) to three steps utilizing sonication method of the present invention and a proper selection of organic solvent, e.g., methanol, ethanol, acetic acid, acetone, acetonitrile, benzene, 1-butanol, 2-butanol, 2-butanone, t-butyl alcohol, carbon tetrachloride, chlorobenzene, chloroform, cyclohexane, 1 ,2-dichloroethane, diethyl ether, diethylene glycol, diglyme (diethylene glycol, dimethyl ether), 1 ,2-dimethoxy-ethane (glyme, DME), dimethylether, dimethyl-formamide (DMF), dimethyl sulfoxide (DMSO), dioxane, ethanol, ethyl acetate, ethylene glycol, glycerin, heptane, Hexamethylphosphoramide, (HMPA), Hexamethylphosphorous, triamide (HMPT), hexane, methanol, methyl t-butyl, ether (MTBE), methylene chloride, N-methyl-2-pyrrolidinone, (NMP), nitromethane, pentane, Petroleum ether (ligroine), 1-propanol, 2-propanol, pyridine, tetrahydrofuran (THF), toluene, triethyl amine, water, water, o-xylene, m-xylene, and p-xylene.

In addition, the use of metallic SWNTs can significantly improve the conductivity and transmittance compared with the use of mixed SWNTs, i.e., unseparated SWNTs. The present invention provides an adhesion mechanism between SWNTs and the surface of a polyethylene naphthalate (PEN) substrate. The π - π stacking effect and hydrophobic interaction are the major contributing factors for CNTs to adhere on the surface of the substrate. Numerous flexible electronic devices require electrically conductive flexible films which are optically transparent to visible light (e.g., 400-700nm wavelength range) (1). Films have been prepared using several coating materials and methods, including semiconducting oxides of: tin indium (2), zinc (3), cadmium (4), or metals such as silver (5). Transparent and electrically conductive coatings on flexible films will be useful for electronic device fabrications particularly for flat panel displays, touch screen panels, solar cells, and polymer light emitting diodes (LEDs) (6-15).

Current transparent conductive coating mainly utilizes Indium Tin oxide (ITO) material which is deposited by chemical vapor deposition (CVD) (16), sputtering or others methods on a substrate, followed by an annealing. ITO films on flexible substrates are inferior in terms of flexibility. Hence, there is a need to find a novel alternative for ITO. Carbon nanotubes (CNTs) are the material of ever-increasing interest due to their excellent electronic, physical, and chemical properties (17-20). The high electrical conductivity of SWNTs is associated only with metallic SWNTs, but all of the available synthesis methods for SWNTs yield mixtures of metallic and semiconducting nanotubes. Moreover, metallic SWNTs generally represent the minority fraction in the mixture (21-22) except the one synthesized from a laser ablation method.

Certain polymeric substrates are much lighter and more flexible than glass substrate while being transparent and are therefore preferred for use over glass substrate for light weight and flexible electronic devices. Recently, polyethylene terephthalate (PET) (23-25) and polyethylene naphthalate (PEN) (26-27) substrates have been reported as potential substrates for the fabrication of polymeric transistors. The two types of polymer films have relatively high optical transmittance at 400-700nm wavelengths which render them suitable as substrate for optical display and plastic electronics applications. In previous published work (23, 28-42), CNTs were dispersed in an aqueous solution using a surfactant (TritonX-100 or SDS) to make a stable solution; however, the surfactant adsorbed on the surface of CNTs will decrease the conductivity since the surfactant will act as an insulator: the surfactant is likely to obstruct the contact among nanotubes and hence prevent them from contacting one another (43). Therefore, removing the surfactant makes the transparent conductive coatings more conductive.

Geng et al made a flexible transparent conductive film on PET substrate using SDS dispersed SWNTs (44). When the film further immersed in various acids, they observed an improvement in the conductivity with a negligible change in transparency. They attributed this enhancement to the removal of surfactant, resulting in a dense film which improved the cross-junction between SWNT networks. The densification of SWNT film improved the conductivity by 25%. To date, however, no convincing results have been reported meeting the performance needed for flexible electronic devices. Sheet resistances in the range of 1,000-30 Ω/sq with a wide range of transmittance 90-50% have been reported (28-42). Part of the variability in results is due not only to the varying sample characteristics of the SWNTs but also the different synthesis methods and purification methods. In addition, there is a trade -off between conductivity and transmittance. When the conductivity goes up, the transmittance goes down, and every research group studies a different system and reports results in different emphasis. Therefore, it is very difficult to refer to published results and draw a firm conclusion.

The present invention provides single walled carbon nanotubes synthesized by different methods and tested to investigate the best candidate SWNT without using surfactant with the flexible substrates. The nanotubes were dispersed in methanol without using surfactant with sonication. A flexible substrate was then dipped into the solution while sonicating to coat SWNTs on film. Several factors, such as purity, type of carbon nanotube, metallic and semiconducting SWNT and different substrates, were evaluated to find the best performance. The present invention provides metallic, purified HiPco SWNTs on a PEN substrate with no surfactant use to achieve the best performance in considering both electrical conductivity and transmittance in the 400-700 nm wavelength range.

A 25 mg sample of SWNTs in 15 mL methanol was prepared without using any surfactant. The mixture was then sonicated with a probe sonicator. This SWNT dispersed solution was then added to a beaker with a 100 mL of methanol. The solution was kept under a continuous bath sonication while dipping a piece of PET (thickness: 175μm) or PEN (125μm) into the solution. The dipping can be repeated or extended for different time to obtain thicker SWNT coating on a film. The coated film was then dried at ambient temperature for 5min.

The present invention provides a composition with high transmittance and high electrical conductivity while using various SWNTs: Purified SWNTs (HiP co), purified SWNTs synthesized from laser ablation, and as-synthesized SWNT from arc discharge and two additional SWNTs samples. Preparations of coated samples were done by coating the substrate on both sides with no surfactant using a dip coating method using PET substrate. The comparison of 4-probe sheet resistance and transmittance for samples prepared using various CNTs with up to three coatings are shown in Table 1.

Sample One coating I Double coatings Triple coatings

Substrate used: PET (control); T %=85 CNI, ^2' Rice University, ^3' Zyvex, ^4' Iljin, Korea and ^5' Clemson University

The SWNTs made by laser ablation gave the lowest sheet resistivity, i.e., the highest conductivity: 185 Ω/sq. This performance is probably due to the fact that it has the highest content of metallic CNT (70%) among the different SWNTs. However, the laser CNT is not commercially available. Therefore, we choose to use the commercially available purified HiPco SWNT in our work. For example, one embodiment of the instant invention provided both side coating with 110 Ω/sq at 88% transmittance using purified single walled nanotubes (SWNTs) coated on a polyethylene naphthalate (PEN) substrate see Table 2.

Substrate used: PEN (control); T %=95.

As the number of coatings on the PET or PEN substrate increase, the conductivity increases but the transmittance decreases. Thus, there is a trade-off between conductivity and transmittance. FIGURE 1 is a photo image of a transparent and conductive purified HiPco SWNT on a flexible PEN substrate. A sheet of paper with printed "UTD" was placed underneath the coated film to illustrate the transparency of the coating. PEN substrate was dipped in the solution while the solution was being bath-sonicated to coat CNTs onto the film. The longer dipping time gave the thicker coating of CNTs (Table 2). This simple coating method was achieved by the proper use of both probe and bath sonication with a good selection of solvent such as methanol. Unlike prior art approaches which require the use of a surfactant (28-42), here we use only a low boiling point solvent such as methanol to coat SWNTs on a flexible substrate.

As mentioned before, the high electrical conductivity should be associated only with metallic SWNTs, and all of the available production methods for SWNTs yield a mixture of metallic and semiconducting carbon nanotubes. Moreover, metallic SWNTs generally represent the minority fraction in the mixtures (statistically 1 :2 for metallic/semiconducting) except SWNT synthesized by the laser ablation method (2:1, respectively). Wang et al (45) demonstrated that semiconducting SWNTs could be extracted from the purified SWNT sample through their preferential interactions with 1-docosyloxymethyl pyrene (DomP) as the planar aromatic agent yields substantially enriched metallic SWNTs. They also reported that when the separated metallic fraction was dispersed in thin conductive polymer film and the metallic SWNTs enhanced electrical conductivity of the resulting nanocomposites significantly, compared with the film made using non-separated purified nanotube sample. The electrical conductivity for the unseparated sample was 2.3.10^"2 S/cm and that for the separated sample 10^"2 S/cm.

The present invention also uses a metallic enriched sample known in the art (e.g., Prof. Sun of Clemson University) for sample preparations. The unseparated SWNT was produced from an arc-discharge method, and both separated metallic and semiconducting nanotube samples were coated on a PET substrate and compared their performances. The comparison in Table 3 clearly shows that the film coated with the metallic SWNT is more conductive than the semiconducting as well as the mixture of SWNTs at the same transmittance level.

Substrate used: PET (control); T %=85

Moreover, the increase in conductivity is about 7 fold between the use of metallic and that of semiconducting one by looking at the conductivity values at 82% transmittance (Table 3 above).

The conductivity of the metallic CNT gives the lowest sheet resistivity (130 Ω/sq) with 80% transmittance with PET (control has 85% transmittance) with both side coatings. The results show that it is a significant challenge to take full advantage of the separated metallic SWNTs for making excellent transparent conductive film with the highest conductivity.

ITO is the preferred choice for conductive coating material on glass substrate. However, ITO has some limitations with flexible substrates: the film coated with ITO is brittle due to inorganic material; therefore, it is a great concern for flexible display applications. It is known that CNTs can resist mechanical test such as bending or crumpling with little loss of conductivity (28). The abuse test with SWNT coated PET showed a slight increase sheet resistivity even after severe bending and crumpling even up to 90° bending.

FIGURE 2 is a graph of the flexibility study of SWNT/PET vs. ITO/PET with two probes resistance. The ITO coated on PET becomes essentially no conductivity upon a 30° bending. As seen in FIGURE 2. We believe the flexibility provided by the use of SWNTs leads to open opportunities for the construction of flexible electronic circuits and devices. The present invention uses PEN and PET substrates, PEN provides better optical transmittance and conductivity with CNT coating than PET does which will be most likely due to the thickness difference. One embodiment of the instant invention provided better CNTs adhesion with PEN. The properties of PEN film are similar to PET but PEN film offers improved performance over PET in the areas of dimensional stability, stiffness, UV weathering resistance, low oligomer content, tensile strength, hydrolysis resistance, and chemical resistance (46).

In addition, the present invention provides a difference of surface energy between PEN and PET by a contact angle measurement. The contact angles for PEN and PET film were measured using a manual goniometer ACEI (Rame-Hart, Inc, model # 50-00-115). With DI water, three droplets at different regions of the same piece of film were used for the measurement, and at least two pieces of films were used in order to obtain reliable contact angle measurement. The PEN film is more hydrophobic with a contact angle of 85 degree compared with the PET film having the angle of 69 degree, and the standard deviation of this measurement was less than 3 degree. The higher hydrophobicity with PEN film is due to the difference in chemical composition between the two substrates. FIGURE 3 is an image of the structures of PEN (left) and PET (right). PEN has more aromatic rings than PET in a unit surface area as seen in Figure 3. In order to further understand the differences shown by the two substrates, AFM surface image study of the substrates coated with SWNT was conducted.

FIGURES 4A-4D are AFM images of PET (FIGURE 4A) and PEN substrates without coating (FIGURE 4B)and (FIGURE 4C) PET and (FIGURE 4D) PEN substrates after 3 minutes of triple time coated with purified HiPco SWNTs. FIGURES 4A and 4B show morphology and roughness of a PET and PEN, respectively. FIGURES 4C and 4D show morphology and roughness of a PET and PEN, respectively after 3min triple time coated with purified HiPco SWNTs. The comparative surface roughness study showed that PEN (4.4 nm) gives less than PET (9.4 nm). This trend does not correlate with the crystallinity of the polymers, i.e., PET and PEN are semi-crystalline with PEN having a higher degree of crystallinity compared to PET due to its more rigid backbone structure. A higher degree of crystallinity often results in a rougher surface (46). The higher surface roughness of the polymer substrate does not favor the adhesion of SWNT but it does in this case. Aromatic compounds are known to interact with graphite, and consequently with the graphitic sidewalls of CNTs (47). This kind of physisorption and noncovalent functionalization of CNT with organic molecules does not significantly perturb the atomic structure of the CNT. In order for a molecule to interact with the nanotube surface, it should contain π bonds to form π stacks and/or it should be able to form a molecular complex also called a π-complex with the electron rich nanotube surface (48). Thus, it is understood that aromatic rings in substrate adheres to the surface of CNT better. In addition, it is believed that the adhesion is strengthened by a hydrophobic interaction as well. To verify this hypothesis, a commercially available microscope glass slide was rinsed with deionized water and then dipped into a mixture of 50 ml concentrated sulfuric acid and 25 ml 30% hydrogen peroxide ('piranha solution') overnight. This generates hydroxyl groups on the surface of the glass and the hydrophilic glass surface yielded no adhering CNT. The fresh hydrophilic surface was thoroughly rinsed with deionized water, and dried. Hydrophobic glass surface was then obtained by immersing the substrate in a 0.1 wt% solution of 1, 8-bistriethoxysilyloctane in hexane for 1 hour and dried. The hydrophobic glass surface generated from the immersion yielded a good adhesion to the film of CNTs. The results indicated that hydrophobic interactions between CNTs and non aromatic hydrophobic surface were weak. The SWNTs were adhered to the surface of aromatic ring containing substrate, is the good compatibility of the hydrophobic SWNTs to the hydrophobic polymer surface of the film. The surface of the PET film was modified to become hydrophilic by a process known as hydrophilization. Surface modification to increase the hydrophilicity of PET surface can be done by either introducing oxygen-containing radical groups or coating hydrophilic polymer chains to the surface of PET. The hydrophilic surface generated on the surface of PET should reduce adhesion between the PET surface and hydrophobic SWNTs. Hydrophilization can be conducted by using one of the several known methods: UV-ozone treatment, chemical oxidation, organic chemical Functionalization, and radiation induced surface grafting. The UV-ozone treatment method uses UV Light and Ozone to both clean and modify the molecular level surface of the solid substrate (49). The chemical oxidation method involves the use of oxidants such as chromic acid, nitric acid, and potassium permanganate to oxidize polymer surface, introducing oxygen-containing groups onto the polymer surface. Ton-That el al have studied the effects of ultraviolet-ozone (UVO) oxidation of polyethylene terephthalate (PET) surface (49). They reported that surface oxygen increases from 26% (untreated) to 37% for the most oxidized surfaces produced. Ultraviolet-ozone (UVO) treatment of PET films was carried out in a SAMCO UV-ozone dry stripper Model UV 1. The reactor contains a quartz high intensity low pressure mercury vapor grid lamp which emits UV light at 185 and 254 nm wavelengths, which are known to excite oxygen to form ozone and atomic oxygen, and also to photosensitize polymer surfaces(50-52).

FIGURE 5 is an AFM image of PET treated with UV-ozone after various times: FIGURE 5 A is an image after 2 minutes, FIGURE 5B is an image after 3 minutes and FIGURE 5C is an image after 5 minutes. PET films were typically treated at a constant distance of approximately 10 cm from the lamp for a range of exposure times (1 to 5 minutes) under atmospheric conditions. The effect of UV-Ozone treatment time vs. PET morphology as measured by AFM is shown in FIGURE 5. There is an increase in mean surface roughness Ra from 3.6 nm on the 2 minutes to 7.3 nm on the 5 minutes treated surface. The contact angle of DI water at the treated PET surface decreases from approximately 76° with increasing irradiation time until it reaches a saturation value at about 30°, which proves an increase of the hydrophilic behavior of the surface with longer irradiation time. UV-ozone treated PET film samples having different treatment time were coated with purified HiPco SWNT for a total of 4 minutes (2 minutes + dry + 2 minutes) and the sheet resistances (4 probe measurement) as well as transmittance of each sample were measured (as seen in Table 4).

The results clearly show that as the treatment of the substrate time increases, sheet resistance as well as transmittance increase. This means that as the treatment time increases, hydrophilicity of PET surface increases so it attracts less hydrophobic CNTs to deposit on PET film. The results support our hypothesis of the adhesion of SWNTs on PET (or PEN) surface due to hydrophobic- hydrophobic interaction.

Thus, a possible mechanism is the good compatibility of the hydrophobic SWNT to the hydrophobic polymer surface of the PET (or PEN). In order for an aromatic compound to interact with the nanotube surface, it should include π bonds to form π stacks and/or to form a molecular complex also called a π-complex with the electron rich nanotube surface. PEN with more aromatic ring in unit surface area vs. PET will give more π stacking with CNTs than PET will. Therefore combining π - π stacking or π- complex plus hydrophobic-hydrophobic interaction are the main contribution factors that provide a good adhesion between SWNTs and

PEN with a little or no effect from the surface roughness.

The present invention provides a coating procedure that reduces the number of steps from five steps to three steps by eliminating the use of a surfactant with a good solvent selection using sonication. For example, many prior art methods use five steps due to the use of a surfactant for CNT dispersion where the need of its removal after coating is necessary since surfactant acts as an insulator. The present invention uses transparent conductive thin films made with various SWNTs and substrates. Transparency and conductivity of different carbon nanotubes after coating on a substrate using dip coating were also evaluated. One embodiment, provides HOΩ/sq at 88% transmittance using a purified SWNT (HiPco) sample with PEN film, and 130Ω/sq at 80% transmittance using metallic enriched SWNT (arc discharge) with PET film. The performance data were measured with both sides coated samples, so once only one side is coated; then its transmittance will be higher than we reported.

In addition, the PEN substrate gave better performance considering both optical transmittance and conductivity than the PET substrate. The better performance with PEN is due to the fact that PEN has higher transmittance and is more hydrophobic than PET and has more π-π stacking effect between SWNTs and its surface in addition to its higher surface smoothness with thinner thickness (125μm vs. 175 μm).

Therefore, based on our study about a possible adhesion mechanism between SWNTs and the substrate, we concluded that π-π stacking effect and hydrophobic-to-hydrophobic interactions are the main factors to have CNTs adhere on the surface of the substrate.

Lastly, the carbon nanotube coated films exhibit good mechanical flexibility that exceeds ITO coated films when films were bent or folded. The flexibility makes CNT coated films be an attractive alternative for constructing flexible electronic devices such as solar cell, OLED and touch panel.

The CNT is a material with a cylindrical shape obtained by rolling up a layer of graphite in which six-membered rings of carbon are linked. A diameter of the CNT is about 1 nm to several tens of nm. In addition, the CNT is classified into a single-walled CNT (SWCNT) including only a single layer, double-walled nanotubes (DWNTs) and a multi-walled CNT (MWCNT) in which multiple layers are formed in a concentric cylindrical shape. As used herein, double- walled nanotubes (DWNTs) and multi-walled nanotubes (MWNT) consist of multiple layers of graphite rolled in on themselves to form a tube shape. Double-walled nanotubes (DWNTs) and multi-walled nanotubes (MWNT) provide similar morphology and properties as compared to SWNT, while improving significantly their resistance to chemicals. SWNTs have a unique property of electrical conductivity and current-carrying capability similar to copper (1, 2), thermal conductivity higher than diamond (3, 4), and mechanical strength higher than any naturally occurring or man-made material (5, 6). Baughman et al. estimate a theoretical elastic modulus of 640 GPa and a tensile strength of 37 GPa (7).

Coating CNT on a substrate: A 25 mg sample of SWNTs (alternatively SWNTs, DWNTs, MWNTs and/or mixtures thereof may be used) was mixed in 25 ml of methanol (or other organic solvent) without using any surfactant. The mixture was then sonicated to disperse the carbon nanotubes with a probe sonicator for 25 minutes at power output of about 45%. This SWNTs dispersed solution was then added to a beaker with 100 ml of methanol. The solution was kept under continuous bath sonication while dipping a piece of a plastic film. This process can be repeated for several times to obtain thicker films. The coated film was dried under ambient conditions. The present invention provides a novel and versatile process for the preparation of carbon nanotubes fibers from various carbon nanotubes layer coated on substrates, e.g., plastic film. This process can be used for the production of various fibers not only from single-walled nanotubes (SWNTs), double-walled nanotubes (DWNTs), or multi-walled nanotubes (MWNTs), but also from the mixtures. Thereof this process can also use both synthesized and purified CNTs. Thus, this robust process of the present invention provides a great potential as a new versatile fabrication method of different CNT fibers and mixtures.

The present invention provides a method of making and a CNT composition and CNT devices having less than 100 Ohm per sq with about 90% transmittance at about 400-700nm wavelength range to be used as a component for electronic devices The performance characteristics of the fibers made by the present invention dependent on the type of carbon nanotubes used and the process conditions. The present invention provides fibers having high mechanical (and electrical) property but also to find a process and formulation with which can be capable to tailor the property of each fiber to be made. With no optimization work, SWNT fibers manually prepared gave as high as 109 MPa of tensile strength and 2.2 GPa of modulus and MWNT fibers gave as high as 89.6 MPa and 6.3 GPa, respectively.

The present invention provides continuous fibers with at least 80-90% of current state-of-the-art fiber's mechanical performance. Additionally, the present invention includes methods of making prepregs and fabrics with the fibers, which can be used for the preparations of nano composites with ceramic, metal and engineering polymer matrix. SWNTs have a unique property of electrical conductivity and current-carrying capability similar to copper (53, 54), thermal conductivity higher than diamond (55, 56), and mechanical strength higher than any naturally occurring or man-made material (57, 58). Baughman et al. estimate a theoretical elastic modulus of 640 GPa and a tensile strength of 37 GPa (59). Technologies for processing CNTs into macroscopic materials are still at a much earlier stage. Macroscopic carbon nanotube fibers have the potential to form high-strength, lightweight, thermally, and electrically conducting structural material at lower cost (60). Some applications such as the space elevator will require ultra-strong SWNT fibers; other applications will require supplementary multifunctional properties and not such high mechanical strength (61). The electrical properties may be use for highly efficient transmission of electricity over long distance. Thermal properties can be exploited in microelectronic applications where thermal management is an increasing problem as miniaturization progress (62). Early studies of CNT -reinforced nano-composites showed that CNTs were effective fillers to enhance the mechanical properties of polymer matrixes (63, 64) but the reinforcement was limited by the quality of dispersion, CNT alignment, and load-transfer efficiency between the CNT and the matrix. Thus, it has been a challenge to make macroscale CNT structures and to fully utilize the outstanding mechanical and other physical properties of CNTs. There are three main types of commercial fiber spinning: melt spinning, dry spinning, and wet solution spinning (65). However, melt spinning CNTs is difficult since CNTs decompose before melting. Most SWNTs fibers have been produced by the solution spinning process. The starting CNTs must be dispersed into a solvent, and the solvent must be extracted after the extrusion to form the solid fiber. Solution spinning can be considered as four steps process: (53) dispersion or dissolution of the fiber material into a solvent, (54) mixing and spinning the dispersion, (55) coagulation and drawing into a solid fiber, and (56) post processing of the fiber through washing, drying, or annealing steps. Fibers of carbon nanotubes micrometers to millimeters long have been produced by variations of chemical vapor deposition (CVD) (64-69).

The first macro-scale CNT structure was in the form of a film called bucky-paper, which displayed relatively high electrical and thermal conductivity, but low mechanical properties (66). For the purpose of obtaining superior mechanical performance, researchers have recently focused on CNT fibers. Gommans et al. have spun fibers electrophoretically from purified laser vaporization grown SWNTs dispersed in N, N-dimethylformamide (DMF) at concentration of about 0.01mg/ml (71). CNTs fiber was successfully prepared through spinning a CNT homogeneous dispersion into a polyvinyl alcohol (PVA) coagulation bath (72). This approach was modified by Baughman's group to make SWCNT composite fibers with very high strength (73, 74). The major issues with this approach include a relatively high fraction of remaining polymer volume and random alignment of CNTs, which limits the fiber's strength, electrical and thermal conductivity (75). Recently, new approaches have been reported in which pure CNT fibers were spun without a matrix. For example, pure CNT fibers were spun from a CNT-fuming sulfuric acid solution (76). A continuous MWCNT yarn was pulled from a high-quality array without twisting (77). SWCNT fibers were spun from an aero-gel in the chemical vapor deposition synthesis zone (78, 79) and MWCNT fibers were spun from CNT arrays with twisting and other techniques (80, 81). These CNT fibers usually have strength of ≤ 1.5 GPa and Young's modulus of ≤ 30 GPa. Miaudet et al (82) prepared CNT/PVA fibers and then stretched them at higher temperature than glass transition temperature of PVA. The drawn fibers possess 1.8 GPa of tensile strength, and 45 GPa of modulus. Dalton et al. (73) modified coagulation-based method. They spun mechanically strong SWNT/PVA gel fiber using co-flowing PVA coagulant pipe. These fibers reach 1.8 GPa of strength and 80 GPa of modulus. These fibers, however, show too low electrical conductivity (0.1-10 S/cm). Because PVA is non-conductive polymer, CNT fibers containing PVA should show low thermal and electrical conductivity. Munoz et al. (83) replaced the PVA coagulant with a polyethlyeneimine (PEI) coagulant. As a result, these fibers can possess 100 ~ 200 S/cm of electrical conductivity, although they have ordinary mechanical properties. Ericson et al. (84) reported that SWNT fiber could be spun using super acid. SWNTs in 102% of sulfuric acid were mixed in the tube and formed themselves into rod-like structure under certain pressure. Mixture was spun into coagulation bath (diethyl ether, 5 wt% aqueous sulfuric acid, or water) and then washed several times. These SWNT fibers possess good mechanical properties, with 120 GPa of modulus, 116 MPa of tensile strength, 21 W/km of thermal conductivity and 5.0 x 10 S/cm of electrical conductivity. Another process to spin SWNT fibers without polymer was introduced by Kozlov et al. (85). This process utilized flocculation principle that dispersed SWNT bundles with anionic surfactant (lithium dodecyl sulfate (LDS)) in the water were aggregated in the strong acid. In contrast to Vigolo's works, flocculation-based process used 37% HCl bath as a flocculation agent. SWNT fibers spun this method have 65 MPag^cm^"3 of a density-normalized specific stress, 12 GPag^cm^"3 of modulus and 140 S/cm of electrical conductivity after annealing at 1000⁰C in flowing argon. All of the literatures published so far show that each process can produce either SWNT fibers or MWNT fibers. In general SWNT fibers were prepared with/without polymer (dispersant) binder from solution process, and MWNT fibers from similar process or dry harvesting from MWNTs forest or solution with dispersant with/without polymer binder use.

The present invention provides a method, with no dispersant/binder, that can produce various fibers not only from single-walled nanotubes (SWNTs), double -walled nanotubes (DWNTs), or multi-walled nanotubes (MWNTs) but also from the mixtures thereof with both as-synthesized and purified form of CNTs. Thus, the fibers prepared from the present invention provide new composition based fibers having outstanding mechanical and other intrinsic physical properties of CN f s, especially, electrical properties since the process does not use either dispersant or polymer binder.

Coating CNT on plastic substrate: A 25 mg sample of SWNTs (alternatively SWNTs, DWNTs,

MWNTs and/or mixtures thereof may be used) was mixed in 25 ml of methanol (or other organic solvent) without using any surfactant. The mixture was then sonicated to disperse the carbon nanotubes with a probe sonicator for 25 minutes at power output of about 45%. This

SWNTs dispersed solution was then added to a beaker with 100 ml of methanol. The solution was kept under continuous bath sonication while dipping a piece of a plastic film. This process can be repeated for several times to obtain thicker films. The coated film was dried under ambient conditions.

Fabrication of CNT fiber: The film coated with CNTs was then dipped in acid for a few seconds. Then the film was soaked in DI water for 1 minute and then in an alcohol solvent and dried at room temperature. The CNT fiber was them drawn from the CNT layer on the film with and/or without twisting. FIGURES 6A-6D are images of CNT coated plastic film and manual Preparation of fiber. FIGURE 1 shows the pictures of SWNTs coated on plastic film, and the SWNTs layer on the film after acid treatment was then used for fiber drawing with/without manual twisting. Fiber was steadily pulled from the CNTs layer with a pair of sharp tweezers. The most preferred physical state of CNTs layer on the film for fiber drawing is most likely dependent on the carbon nanotubes qualities such as kind of CNT, its purity, length, aspect ratio, defects, chirality and post treatment of fiber drawn. Fiber quality is also dependent on the degree of alignment during the drawing process and post treatment.

FIGURES 7A and 7B are SEM images of SWNTs coated on plastic film where FIGURE 7A is a SEM image before acid treatment and FIGURE 2b is a SEM image after acid treatment. FIGURES 7A and 7B show SEM images of a SWNTs coated film before and after an acid treatment, where they show that after the treatment, CNTs layer became dense.

FIGURE 8 shows the SEM images of a SWNTs fiber that was initially drawn from a SWCNT layer on film followed by manual twisting. FIGURES 3a and 3b are SEMs images of SWNT fiber with a 60-70 μm diameter fiber, ivcrs primitive hand-twisting significantly decreases the diameter of the CNT Obert, from 400μm Io 50μm level. The hatsd-twi&tmg wiSl bring the CKTs in closer contact to among adjacent CM\ and therefore enhances Van Der Waals forces, and reduces friction among CYL*>, which improves the load transfer among the CMs. It will also affect on electrical conductivity of the fiber.

FIGURE 9 shows SEM images of a MWNT fiber that were initially pulled from a MWCNT coated film followed by twisting by hands. FIGURES 4a and 4b are SEMs of MWN T fiber with a 50μm Diameter. The quality of the fiber is likely associated with the thickness of the coatings (e.g., diameter of fiber) as well. It shows that elongation property varies: 160-300% for SWNT fibers and 150-190% for MWNTs fibers as shown in Table 1.

Table 1. Diameter vs. Elongation:

FIGURE 10 shows the test results of tensile strength and Young's modulus of a SWNT fiber made from a film coated with SWNTs for 3 minute dipping. FIGURES 5a is a graph of the tensile strength and Young's modulus of SWNT fiber prepared from SWNT coated on film. Based on our limited tests with no optimization work, we found that a SWNT fiber manually prepared so far gave as high as 109MPa of tensile strength and 2.2 GPa of modulus and a MWNT fiber gave as high as 89.6 MPa and 6.3 GPa, respectively. This initial promising fiber making results with both SWNTs and MWNTs encourages us to seek for more detailed research of this new process that can be expanded for the fiber preparation of SWNTs, DWNTs, MWNTs as well as mixture thereof. The present invention provides outstanding physical properties, especially, mechanical property using this new process having the dynamic versatility of the different CNTs use. Table II: SWNT & MWNT Fibers: Mechanical Properties from Literature. Table II:

Without the use of dispersant or polymer binder, the present invention provides various fibers not only from single-walled nanotubes (SWNTs), double-walled nanotubes (DWNTs), or multi- walled nanotubes (MWNTs) but also from the mixtures thereof with both as-synthesized and purified form of the CNTs. The present invention provides a potential to prepare unique fibers having different coirsposihon and outstanding physical properties such as mechanical and/or electrical property

It is contemplated that any embodiment discussed in this specification can be implemented with respect to any method, kit, reagent, or composition of the invention, and vice versa. Furthermore, compositions of the invention can be used to achieve methods of the invention.

It will be understood that particular embodiments described herein are shown by way of illustration and not as limitations of the invention. The principal features of this invention can be employed in various embodiments without departing from the scope of the invention. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, numerous equivalents to the specific procedures described herein. Such equivalents are considered to be within the scope of this invention and are covered by the claims.

All publications and patent applications mentioned in the specification are indicative of the level of skill of those skilled in the art to which this invention pertains. All publications and patent applications are herein incorporated by reference to the same extent as if each individual publication or patent application was specifically and individually indicated to be incorporated by reference.

The use of the word "a" or "an" when used in conjunction with the term "comprising" in the claims and/or the specification may mean "one," but it is also consistent with the meaning of "one or more," "at least one," and "one or more than one." The use of the term "or" in the claims is used to mean "and/or" unless explicitly indicated to refer to alternatives only or the alternatives are mutually exclusive, although the disclosure supports a definition that refers to only alternatives and "and/or." Throughout this application, the term "about" is used to indicate that a value includes the inherent variation of error for the device, the method being employed to determine the value, or the variation that exists among the study subjects.

As used in this specification and claim(s), the words "comprising" (and any form of comprising, such as "comprise" and "comprises"), "having" (and any form of having, such as "have" and "has"), "including" (and any form of including, such as "includes" and "include") or "containing" (and any form of containing, such as "contains" and "contain") are inclusive or open-ended and do not exclude additional, unrecited elements or method steps.

The term "or combinations thereof as used herein refers to all permutations and combinations of the listed items preceding the term. For example, "A, B, C, or combinations thereof is intended to include at least one of: A, B, C, AB, AC, BC, or ABC, and if order is important in a particular context, also BA, CA, CB, CBA, BCA, ACB, BAC, or CAB. Continuing with this example, expressly included are combinations that contain repeats of one or more item or term, such as BB, AAA, MB, BBC, AAABCCCC, CBBAAA, CABABB, and so forth. The skilled artisan will understand that typically there is no limit on the number of items or terms in any combination, unless otherwise apparent from the context.

All of the compositions and/or methods disclosed and claimed herein can be made and executed without undue experimentation in light of the present disclosure. While the compositions and methods of this invention have been described in terms of preferred embodiments, it will be apparent to those of skill in the art that variations may be applied to the compositions and/or methods and in the steps or in the sequence of steps of the method described herein without departing from the concept, spirit and scope of the invention. All such similar substitutes and modifications apparent to those skilled in the art are deemed to be within the spirit, scope and concept of the invention as defined by the appended claims.

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Claims

CLAIMS:

1. A method of making a carbon nanotubes fiber comprising the steps of: combining a carbon nanotube and a non-surfactant organic solvent to form a nanotube solution; dispersing the carbon nanotubes in the nanotube solution; contacting a substrate with the nanotube solution to form a nanotube coated substrate; optionally re-contacting the nanotube coated substrate to apply additional nanotube coats to the nanotube coated substrate; and contacting the nanotube coated substrate with an acid solution; contacting the nanotube coated substrate with water; exposing the nanotube coated substrate to an alcohol source; and drying the nanotube coated substrate; and drawing a nanotube fiber from the nanotube coated substrate.

2. The method of claim 1, further comprising the step of twisting the nanotube fiber as it is drawn.

3. The method of claim 1, wherein the carbon nanotube is a single-walled nanotube, double- walled nanotube, multi-walled nanotube or a mixture thereof.

4. The method of claim 1, wherein the carbon nanotube has less than 100 Ohm per sq

5. The method of claim 1, wherein the carbon nanotube has about 90% transmittance or less than 90% transmittance at about 400-700nm wavelength.

6. A method of manufacturing a carbon nanotube fiber comprising the steps of: combining a carbon nanotube and a non-surfactant organic solvent to form a nanotube solution; dispersing the carbon nanotubes in the nanotube solution; contacting a substrate with the nanotube solution to form a nanotube coated substrate; optionally re-contacting the nanotube coated substrate to apply additional coatings to the nanotube coated substrate; and drying the nanotube coated substrate.

7. The method of claim 6, wherein the carbon nanotube comprises a single-walled nanotube, double-walled nanotube, multi-walled nanotube or a mixture thereof.

8. The method of claim 6, wherein the substrate is a plastic substrate.

9. The method of claim 6, wherein the substrate is a plastic film.

10. The method of claim 6, wherein the dispersion occurs by sonicated.

11. The method of claim 6, wherein the carbon nanotube has less than 100 Ohm per sq

12. The method of claim 6, wherein the carbon nanotube has about 90% transmittance or less than 90% transmittance at about 400-700nm wavelength.

13. A composition made by the method of claim 6.

14. A method of coating carbon nanotubes on a substrate comprising the steps of: combining a carbon nanotube and a non-surfactant organic solvent to form a nanotube solution; dispersing the carbon nanotubes in the nanotube solution; contacting a substrate with the nanotube solution to form a nanotube coated substrate; optionally re-contacting the nanotube coated substrate to apply additional coatings to the nanotube coated substrate; and drying the nanotube coated substrate.

15. The method of claim 14, wherein the carbon nanotube is a single-walled nanotube, double- walled nanotube, multi-walled nanotube or a mixture thereof.

16. The method of claim 14, wherein the substrate is a plastic substrate.

17. The method of claim 14, wherein the substrate is a plastic film.

18. The method of claim 14, wherein the dispersion occurs by sonicated.

19. A method of coating a substrate with carbon nanotubes comprising the steps of: providing a substrate; contacting the substrate with a nanotube solution comprising one or more carbon nanotubes and a non-surfactant contained organic solvent; coating the one or more carbon nanotubes on at least a portion of the substrate to form a carbon nanotube layer on a nanotube coated substrate; and re-contacting optionally the substrate with the nanotube solution to apply additional nanotube coats to the nanotube coated substrate.

20. The method of claim 19, wherein the nanotube solution is prepared by a sonication.

21. The method of claim 19, wherein the nanotube solution is prepared without using a surfactant.

22. The method of claim 19, wherein the substrate comprises a plastic film having a hydrophobic property.

23. The method of claim 19, wherein the substrate comprises polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polycarbonate, polyolefm or thermo-plastic olefin (TPO).

24. The method of claim 19, wherein the substrate is coated on a single side.

25. The method of claim 19, wherein the substrate has one or more coating layers on each side.

26. The method of claim 19, wherein the carbon nanotube is a single-walled nanotube, double- walled nanotube, multi-walled nanotube or a mixture thereof.

27. The method of claim 19, wherein the carbon nanotube layer has less than 200 Ohm per sq.

28. The method of claim 19, wherein the carbon nanotube layer has between 0 and 99.5% transmittance at about 400-700nm wavelength.

29. A high transmittance and high electrical conductivity composition comprising: a substrate having one or more carbon nanotube layers deposited on at least a portion of a substrate surface and the carbon nanotube layer has less than 1000 Ohm per sq.

30. The composition of claim 29, wherein the carbon nanotube layer has less than 300 Ohm per sq.

31. The composition of claim 29, wherein the substrate comprises a plastic film having a hydrophobic property.

32. The composition of claim 29, wherein the substrate comprises polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polycarbonate polyolefm or thermo-plastic olefin

(TPO).

33. The composition of claim 29, wherein thermo-plastic olefin (TPO) comprises polymer/filler blends usually consisting of some fraction of PP (polypropylene), PE (polyethylene), BCPP (block copolymer polypropylene), rubber, and a reinforcing filler.

34. The composition of claim 29, wherein the carbon nanotube is a single-walled nanotube, double-walled nanotube, multi-walled nanotube or a mixture thereof.

35. The composition of claim 29, wherein the one or more carbon nanotube layers have less than 200 Ohm per sq.

36. The composition of claim 29, wherein the one or more carbon nanotube layers have between 0 and 99.5% transmittance at about 400-700nm wavelength.

37. A high transmittance and high electrical conductivity carbon nanotube layered substrate comprising the steps of: providing a substrate; contacting the substrate with a nanotube solution comprising one or more high transmittance and high electrical conductivity carbon nanotubes and a non-surfactant contained organic solvent; coating the one or more carbon nanotubes on at least a portion of the substrate to form a the nanotube coated substrate having one or more carbon nanotube layers; and re-contacting optionally the substrate with the nanotube solution to apply additional layers of the one or more high transmittance and high electrical conductivity carbon nanotubes to the one or more carbon nanotube layers.

38. The composition of claim 37, wherein the substrate comprises a plastic film having a hydrophobic property.

39. The composition of claim 37, wherein the substrate comprises polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polycarbonate or thermo-plastic olefin (TPO).

40. The composition of claim 37, wherein the carbon nanotube is a single-walled nanotube, double-walled nanotube, multi-walled nanotube or a mixture thereof.

41. The composition of claim 37, wherein the one or more carbon nanotube layers have less than 200 Ohm per sq. and between 0 and 99.5% transmittance at about 400-700nm wavelength.