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High-Strength Single-Walled Carbon Nanotube/Permalloy Nanoparticle/Polyvinyl Alcohol Multifunctional Nanocomposite Fiber Gengheng Zhou, Yi-Qi Wang, Joon-Hyung Byun, Jin-Woo Yi, Sang-Su Yoon, Hwa-Jin Cha, Jea-Uk Lee, Youngseok Oh, Byung-Mun Jung, Ho-Jun Moon, and Tsu-Wei Chou ACS Nano, Just Accepted Manuscript • DOI: 10.1021/acsnano.5b05404 • Publication Date (Web): 02 Oct 2015 Downloaded from http://pubs.acs.org on October 8, 2015

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Strong Single-Walled Carbon Nanotube/Permalloy Nanoparticle/Polyvinyl Alcohol Multifunctional Nanocomposite Fiber Was Fabricated by Wet Spinning. 300x150mm (150 x 150 DPI)

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High-Strength Single-Walled Carbon Nanotube/Permalloy Nanoparticle/Polyvinyl Alcohol Multifunctional Nanocomposite Fiber Gengheng Zhou*,†, Yi-Qi Wang†┴, Joon-Hyung Byun*,†, Jin-Woo Yi†, Sang-Su Yoon†, HwaJin Cha†, Jea-Uk Lee†, Youngseok Oh*†, Byung-Mun Jung†, Ho-Jun Moon,‡ and Tsu-Wei Chou§ †

Korea Institute of Materials Science, 797 Changwondaero, Changwon 642-831, South Korea E-mail: [email protected], [email protected], [email protected] ‡ NanoSolution Co., Ltd., 817 Palbokdong 2-9a, Deokjin-gu, Jeonju-si, 561-844, South Korea § Department of Mechanical Engineering, University of Delaware, Newark, DE 19716, USA ┴ School of Mechanical Engineering, Dalian University of Technology, Dalian 116024, China ABSTRACT Magnetic nanocomposite fibers are a topic of intense research due to their potential breakthrough applications such as smart magnetic-field-response devices and electromagnetic interference (EMI) shielding. However, clustering of nanoparticles in a polymer matrix is a recognized challenge for obtaining a property-controllable nanocomposite fiber. Another challenge is that the strength and ductility of the nanocomposite fiber decrease significantly with increased weight loading of magnetic nanoparticles in the fiber. Here, we report highstrength single-wall carbon nanotube (SWNT)/permalloy nanoparticle (PNP)/polyvinyl alcohol (PVA) multifunctional nanocomposite fibers fabricated by wet spinning. The weight loadings of SWNT and PNP in the fiber were as high as 12.0 % and 38.0 %, respectively. The tensile strength of the fiber was as high as 700 MPa, and electrical conductivity reached 96.7 S m-1. The saturation magnetization (Ms) was as high as 24.8 emu g-1. The EMI attenuation of a fabric woven from the prepared fiber approached 100% when tested with electromagnetic waves with frequency higher than 6 GHz. The present study demonstrates that a magneticfield-response device can be designed using the fabricated multifunctional nanocomposite fiber. Keywords: Single-walled carbon nanotube, permalloy nanoparticle, polyvinyl alcohol, magnetic fiber, wet spinning, electromagnetic interference shielding

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Stimuli-responsive materials have drawn increasing interest in the past few decades due to their potential applications in smart devices.1, 2 Magnetic stimuli-responsive triggers which changed the shape under magnetic field, are one of the most common applications.3 Among these applications, a magnetic composite fiber is a unique type of material made of magnetic nanoparticles (MNPs) in a polymer matrix.3, 4 The magnetic properties are determined by the implemented magnetic fillers and their content in the fiber.5, 6 However, clustering of nanoparticles in a polymer matrix is a recognized challenge in obtaining property-controllable MNP/polymer nanocomposites.7 Another challenge is that the strength and ductility of the nanocomposite fiber decrease significantly with increased MNP loading in the fiber.8, 9 Considerable efforts have been devoted to solve these problems. One approach employs a surface modification process wherein silk fibers were coated by magnetic nanoparticles.10 However, the magnetic property was not presented in this work. Another route applies a wet spinning process, in which iron oxide was synthesized and mixed with a polymer solution and a fiber was fabricated by wet spinning.5, 11 The maximum loading of iron oxide in the composite fiber can reach 15 wt.%. A third route adopts an electrospinning method, wherein CoFe2O4 or Fe3O4 nanoparticles were mixed with a polymer solution using sonication, and magnetic nanofibers were fabricated by electrospinning.7, 12-14 Although great improvement has been achieved, the magnetic and mechanical properties are far from satisfactory, and these challenges remain key issues for fabricating advanced functional nanocomposite fibers. Better magnetic properties are required for applications such as shielding the magnetic field using magnetic composite fiber textiles and smart devices. In addition to their functional properties, advanced nanocomposites have attracted extensive interest for their light weight and high strength. SWNT are one of the most promising nanofillers as reinforcements in nanocomposites due to their exceptional mechanical properties.14, 15-19 To utilize these outstanding properties of SWNTs on a macroscopic scale, considerable efforts have been made to fabricate neat SWNT fibers and SWNT/polymer 2 ACS Paragon Plus Environment

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fibers.20-34 However, the purification process of SWNTs through the removal of amorphous carbons (ACs) and catalyst particles makes the costs extremely high, which severely hampers their large-scale application.35 Generally, the catalysts used in SWNT fabrication are transition metals with magnetic properties, such as iron, cobalt and nickel. Instead of removing the catalysts, we have developed a novel approach to take advantage of their magnetic properties. In this communication, we report a strong SWNT/permalloy/PVA multifunctional nanocomposite fibers, which overcomes all of the challenges mentioned above. To optimize the magnetic properties of the SWNT and MNP powders, permalloy particles with high magnetic permeability were selected for use as a catalyst in the SWNT fabrication by an arcdischarge method.36 Nanopowders consisting of uniformly dispersed permalloy nanoparticles (PNPs), SWNTs and ACs were obtained. A heat treatment at 400 °C in air for two hours was applied to remove the AC. Then, a further reduction treatment at 730 °C in H2 for another two hours was carried out to obtain SWNT and PNP nanopowders. The prepared nanopowders were then used as nanofillers in a PVA solution with sodium dodecyl sulfate (SDS) as a surfactant.37 Finally, a strong multifunctional SWNT/PNP/PVA nanocomposite fiber was fabricated by wet spinning from the prepared solution. The weight ratios of SWNTs and PNPs in the fiber were up to 12.0 wt.% and 38.0 wt.%, respectively, which were by far higher than those previously reported. 5-14 Due to the high SWNT content, the SWNT/PNP/PVA fiber achieved a tensile strength up to 700 MPa, and an electrical conductivity of 96.7 S m-1. Because of the high loading of PNP, the saturation magnetization (Ms) of the fiber was up to 24.8 emu g-1. Magnetic stimuli-responsive triggers have been designed by using the multifunctional fiber. In addition, the EMI attenuation of the fabric woven from the prepared fiber approached 100% when tested by electromagnetic waves with frequencies higher than 6 GHz. RESULTS AND DISCUSSION


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Figure 1a shows a sketch of the fabrication process for the SWNT/PNP powders by the arc-discharge method. Permalloy particles were selected as a catalyst and embedded in a graphite cathode. The anode material was pure graphite and a voltage (35-40 V) was applied between the two electrodes under a vacuum condition (80-120 torr). SWNT/PNP nanopowders shown in Figure 1b were collected between the electrodes. The high-resolution transmission electron microscope (HRTEM) image in Figure 1b1 shows that PNPs of 20 nm in diameter, which were wrapped by spherical ACs, were uniformly dispersed with SWNTs, as denoted by arrows (See the detailed analysis in the Supporting Information). Figure 1c shows the morphology of the fabricated nanopowders after heat treatment at 400 °C in air for two hours. A corresponding HRTEM image in Figure 1c1 illustrates that the ACs were removed during the heat treatment. The PNPs changed to permalloy oxide nanoparticles (PONP) during this process. Figure 1d shows the morphology of the nanopowder with a further heat treatment at 730 °C in H2 for two hours. It can be seen that ACs were completely removed, and that the PNPs were uniformly dispersed with the SWNTs. The HRTEM image in Figure 1d1 indicates that the size of the PNPs increased from 20 nm to about 50 nm. The as-fabricated nanopowders and the heat-treated powders under these two conditions (heat treatment at 400 °C and further treatment at 730 °C) were defined as powders A, B and C, respectively. To quantitatively analyze the component of these powders, thermogravimetrical analysis (TGA) was performed under air at 5 °C min-1 in the range of 30 to 1000 °C. The TGA curves of the powders A, B and C are shown in Figure 1e. The weight losses of powders A, B and C illustrates that the ACs were completely removed in the case of the two-step heat treatment (powder C). The quantitative weight ratios of SWNT and PNP in powder C were 24.0% and 76.0%, respectively (Table S1). Figure 2a shows the wet spinning process of the SWNT/PNP/PVA nanocomposite fibers. First, SDS was dissolved in distilled water by sonication for two minutes. The fabricated powder C (SWNT/PNP powder) was dispersed in the solution by sonication for one hour. Next, PVA 4 ACS Paragon Plus Environment

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particles were added into the solution, and the solution was heated to 95 °C under sonication for thirty minutes. Finally, the prepared suspension was extruded into a coagulation solution by a syringe through a spinneret with diameter of 160 µm, and continuous filament was collected on a paper drum (Movie S1). Acetone was selected as the coagulation solution to replace water and remove the SDS surfactant. Figure 2b shows the cross-sectional morphology of the fiber and the surface morphology, respectively. The diameter of the fiber is about 18 µm, with a smooth and uniform surface. Significant shrinkage of the failure cross section illustrates good plasticity. To evaluate the mechanical property of the fiber, failure strength of the fiber was measured by a single filament tensile test method;38 the detailed process can be found in the Supporting Information. A typical stress- strain curve is shown in Figure 2c. The failure strength was up to 700 MPa. The magnetic property of the fiber was measured by a vibrating-sample magnetometer (VSM) as shown in Figure 2d. Due to high PNP content (38.0 wt.%), the Ms of the fiber reaches to 24.8 emu g-1. The performance of our fiber is compared with the values reported in the literature for magnetic composite fibers made by different methods and shown in Figure 2e. Compared to the PVA/MNP fibers, 11 the failure strength of our SWNT/PNP/PVA nanocomposite fiber is improved by three times due to the reinforcement of SWNTs. Because of the high content of PNPs (38.0% wt.%) with superior magnetic property, the Ms of the fiber is about four times higher than the similar PVA/MNP nanocomposite fibers.11-14 To investigate the EMI shielding performance of the nanocomposite fiber, a preliminary test was conducted. The EMI shielding effectiveness (SE) of a material, which is the ability to reflect and/or absorb the EM radiation, can be expressed in terms of the ratio of incoming to outgoing power. The EMI SE of a material depends on three mechanisms: reflection of the EM wave from the front face of the shield; absorption of the wave when it passes through the shield and multiple reflections of the wave. It can be expressed by Equation 1. 5 ACS Paragon Plus Environment

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(1)

SE=R+A+B

Here, R is the reflection loss, and A is the absorption loss. B is the multiple reflection loss, which is negligible compared to R and A.39 Figure 3a shows SWNT/PNP/PVA fabrics woven from the nanocomposite fiber bundles of 25 filaments. A dense or sparse fabric structure can be obtained by using a laboratory-scale weaving machine. The dense fabric and the sparse fabric were 42×9 fiber bundles/cm2 and 8 ×9 fiber bundles/cm2 respectively. A small magnet (1.5 g) tightly stuck on a small SWNT/PNP/PVA fabric (0.5 g) in Figure 3b shows superior magnetic performance of the fabric (Movie S2). To examine the EMI performance of the multifunctional fiber, a dense fabric structure (50×50 mm2) was selected and measured by a micro-strip line method.40 A vector network analyzer was used to measure the scattering parameters of the nanocomposite fabric (Figure 3c and d).The incident signal parallel to the wave direction is denoted by an arrow. The frequency range was set from 0 to 10 GHz. The EMI attenuation was calculated from the measured scattering parameters (Figure 3d) by the ratio of power loss (Ploss) shielded by the nanocomposite fabric to the incident power (P0) of the electromagnetic wave. To make a comparison, we tested another type of fabric, which was woven from normal nanocomposite fibers using commercial SWNT powders as nanofillers (denoted as SWNT/MNP/PVA in Figure 3e). Figure 3e shows the power loss ratio of the incident signal with different frequency. It can be seen that the SWNT/PNP/PVA fabric has a much better EMI shielding performance than that of the SWNT/MNP/PVA fabric. The power loss approaches 100 percent at frequencies higher than 6 GHz. This excellent performance of EMI SE of the fabricated SWNT/PNP/PVA nanocomposite fabric can be attributed to the following reasons. Firstly, a uniform dispersion and distribution of highly conducting SWNTs with a high loading (12.0 wt.%) in the PVA matrix was achieved. Therefore, an electrically conducting 3D network was formed in the fiber, and the electrical 6 ACS Paragon Plus Environment

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conductivity was up to 96.7 S m-1, which resulted in significant enhancement of the reflection loss. Secondly, due to our special treatment of nanopowders, the high loading (38.0 wt.%) of PNPs was uniformly dispersed in the fiber. Since permalloy possesses a high magnetic permeability,36 the EM energy absorption and dissipation capability were greatly improved, resulting in the enhancement of microwave shielding effectiveness. Finally, it is also worthwhile to point out that the incorporation of SWNTs and PNPs into the PVA matrix improved not only the electrical conductivity but also the dielectric properties via interfacial polarization (due to the significant difference in electrical conductivity of the SWNTs, PNPs and PVA). The polarization and relaxation phenomenon would also contributed to the absorption loss, which further improved the shielding performance of the fabric. It is important to note that the thickness of the SWNT/PNP/PVA fabric (~370.0 µm) is sufficiently thin to provide a desired level of EM attenuation. These findings are of particular interest in designing a shielding material in high-tech areas such as defense, aerospace or medical care. The conductive network formation by the high SWNT content in the fiber provides a good electrical conductivity.16, 19 A simple device was designed to demonstrate the magnetic response and the electrical conductive performance of the fiber as shown in Figure 4. To obtain a helix structure, twenty filaments were simultaneously extruded into the coagulation solution and collected on a screw and then dried in air at room temperature. The helical fiber spring was fixed on one end of a copper wire by silver paste in an open circuit as shown in Figure 4a (top view) and 4b (side view). The circuit will close if the fiber spring deforms and is in contact with the copper plate as shown in Figure 4c (top view) and 4d (side view). A LED lamp was connected in series to demonstrate the opening or closing of the circuit. Two small magnets, which were fixed on a pivoting steel bar, were used to generate a magnetic field. By rotation, these magnets can be positioned to be under the fiber spring or move away from it and a relatively strong and weak magnetic field can be generated near the fiber spring. The magnetic fields near the fiber spring surface were measured by a Gauss/Teslameter and 7 ACS Paragon Plus Environment

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were shown in Figure S5. The SWNT/PNP/PVA fiber spring deforms under the magnetic field (690 Gauss) when one of the magnets moves below it. When the deformed fiber spring is in contact with the copper plate, a closed circuit is formed, and the lamp is lit (See Figure 4c and 4d). Once the magnetic field is removed, the magnetic field decreased to be 77.0 Gauss and the fiber spring recovers and the circuit is in an open state, and the lamp is turned off. A detailed demonstration video was supplied in the Supporting Information (Movie S3). Owing to the fiber flexibility, the tunable mechanical properties and the quick response to external stimuli, it is expected that smart stimuli-responsive designs may be achieved. CONCLUSIONS In summary, we have developed a simple and effective wet spinning process to fabricate a continuous multifunctional SWNT/PNP/PVA composite fiber. Uniformly dispersed PNPs with SWNTs were achieved by an arc-discharge process using permalloy particles as a catalyst. TEM observations confirmed that the PNPs and SWNTs were uniformly dispersed in the PVA solution using SDS as a surfactant. Scanning electron microscopy images revealed that the nanocomposite fiber possesses a smooth surface and uniform morphology. As a multifunctional material, the SWNT/PNP/PVA fiber achieved a high tensile strength, up to 700 MPa, an electrical conductivity of 96.7 S m-1 and magnetic property with an Ms of 24.8 emu g-1. The EMI attenuation of the fabric, which was woven from the prepared fiber, approached to 100% when tested by electromagnetic wave with frequencies higher than 6 GHz. These properties can be accurately tailored by adjusting the loading of the SWNTs and PNPs. Success in the development of the multifunctional nanocomposite fibers by wet spinning with specially designed suspension showed a promising pathway to connect nanoscale effects to macrostructure performance. Combining the fiber’s high strength with functional characteristics such as electrical conductivity and magnetic properties, one can therefore anticipate future development of smart stimuli-responsive devices, multifunctional textiles for EMI shielding and other novel applications. 8 ACS Paragon Plus Environment

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METHODS Synthesis of SWNT/PNP powder: SWNT/PNP powders were produced by the arc-discharge method with permalloy particles embedded in a graphite cathode as a catalyst. Another graphite electrode was selected, and a voltage (35-40 V) was applied between two electrodes under a vacuum condition (80-120 torr). SWNT/PNP nano-powders were collected between the electrodes. To remove amorphous carbons, as-produced powders were heat treated at 400 °C in air for two hours. A reduction process was then carried out with further heat treatment at 730 °C in H2 for two hours to obtain SWNT/PNP powders. The SWNT and PNP contents were determined by TGA (TA Q500) with a heating rate of 5 °C/min from 25 °C to 1000 °C in air. Suspension preparation and wet spinning: SDS (Sigma-Aldrich) was used as a surfactant to obtain uniformly dispersed SWNT/PNP powders. The weight ratio of SDS to SWNT/PNP powders was optimized to be 4:1. Firstly, SDS (2 g) was dissolved in distilled water (50 ml) by sonication for two minutes. Then, the fabricated SWNT/PNP powders (0.5 g) were dispersed in the SDS solution by sonication for 1 hr. After that, PVA (Sigma-Aldrich, molecular weight: 146,000~186,000; 99+% hydrolyze) particles with desired weight were added into the prepared solution and heated to 95 °C under sonication for thirty minutes. To obtain different weight ratios of SWNT/PNP powders to PVA, different amounts of PVA (0.8 g, 0.5 g and 0.3 g) were added into the suspensions, which were previously prepared with the same amount of SWNT/PNP (0.5 g) and distilled water (50 ml) as mentioned before. The weight ratios of SWNT/PNP powders to PVA of the prepared suspensions were 1:1.6, 1:1 and 1:0.6, respectively. Detailed contents of the SWNT/PNP powders and PVA in the suspensions are summarized in Supporting Information Table 2. Finally, the prepared suspension was extruded into a coagulation solution by a syringe through a spinneret of 160.0 µm in diameter. Acetone was selected as a coagulation solution, and the SDS surfactant was removed by


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acetone simutaneously. Then, continuous filament was collected on a paper drum (Supporting Information Movie S1). Characterization: A JSM-5800 scanning electron microscopy was used to observe the morphology of the SWNT/PNP/PVA fiber. Morphologies of SWNT/PNP powders were observed by a high-resolution transmission electron microscope (JEOL 2100F) operated at 200 kV. Crystal structures of the PNPs were studied by selected area electron diffraction patterns. Morphologies of the SWNTs and PNPs were observed by low-magnification and high-resolution TEM images. TEM samples were prepared as follows. SWNT/PNP powders were dispersed in distilled water with SDS as a surfactant. Then, a small drop of the prepared suspension was extracted by a pair of tweezers with a sharp tip and dropped on a TEM copper grid. Magnetic property characterization: The saturation magnetization of the fiber was measured by a VSM (Quantum Design Versalab) at room temperature. Fiber was first chopped into small sections and put into a plastic tube. Then hysteresis loop was measured by VSM and saturation magnetization was calculated. Magnetic field measurement: The magnetic fields near the fiber spring surface were measured by a Gauss/Teslameter. Detailed information was given in the Supporting Information. Tensile test: Stress-strain curves of the composite fiber were obtained from TA Instruments Q800 Dynamic Mechanical Analyzer (DMA). Detailed information can be found in the Supporting Information. Magnetic fields measurement: The magnetic fields near the fiber spring with different distance to the magnet were measured by a Gauss/Teslameter (Model 6010, F.W. Bell). Detailed information can be found in the Supporting Information. Conflict of Interest: The authors declare no competing financial interest. Acknowledgements. This research was supported by Global Research Lab Program and Basic Science Research Program through the National Research Foundation of Korea (NRF) funded 10 ACS Paragon Plus Environment

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by the Ministry of Science, ICT & Future Planning (NRF-2007-00017 and NRF2015R1C1A1A02037139). J. Byun, G. Zhou and Y. Oh designed the project. G. Zhou conducted the experiments as well as collected and analyzed data. G. Zhou, J. Byun and Y. Oh wrote the manuscript. H. Moon fabricated the SWNT/PNP powder; J. Yi carried out the EMI test; Y. Wang, S. Yoon, H. Cha, J. Lee, B. Jung and T. Chou provided valuable technical and conceptual advice. Supporting Information Available: The Supporting Information is available free of charge on the ACS Publications website at http://pubs.acs.org REFERENCES AND NOTES [1] Huang, C.; Soenen, S. J.; Rejman, J.; Lucas, B.; Braeckmans, K.; Demeester, J.; De Smedt, S. C. Stimuli-Responsive Electrospun Fibers and Their Applications. Chem. Soc. Rev. 2011, 40, 2417-2434. [2] Ghosh, S.; Puri, I. K. Soft Polymer Magnetic Nanocomposites: Microstructure Patterning by Magnetophoretic Transport and Self-Assembly. Soft. Matter. 2013, 9, 2024-2029. [3] Thévenot, J.; Oliveira, H.; Sandre, O. Lecommandoux, S. Magnetic Responsive Polymer Composite Materials. Chem. Soc. Rev. 2013, 42, 7099-7116. [4] Hernández, R.; López, G.; López, D.; Vázquez, M.; Mijangos, C. Magnetic Characterization of Polyvinyl Alcohol Ferrogels and Films. J. Mater. Res. 2007, 22, 22112216. [5] Chien, A. T.; Newcomb, B. A.; Sabo, D.; Robbins, J.; Zhang, Z. J.; Kumar, S. HighStrength Superparamagnetic Composite Fibers. Polymer 2004, 55, 4116-4124. [6] Longo, A.; Wang, X. L.; Ruotolo, A.; Peluso, A.; Carotenuto, G.; Lortz, R. Effect of The Polymeric Matrix on The Structural and Magnetic Properties of Hematite/Polymer Composites. J. Nanopart. Res. 2012, 14, 1-8. [7] Reddy, K. R.; Park, W.; Sin, B. C.; Noh, J.; Lee, Y. Synthesis of Electrically Conductive 11 ACS Paragon Plus Environment

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The Mechanical Properties of Carbon Nanotube-Polymer Composites. Carbon 2006, 44, 1624-1652. [18] Minus, M. L.; Chae, H. G.; Kumar, S. Single Wall Carbon Nanotube Templated Oriented Crystallization of Poly(Vinyl Alcohol). Polymer 2006, 47: 3705-3710. [19] De Volder, M. F. L.; Tawfick, S. H.; Baughman, R. H.; Hart, A. J. Carbon Nanotubes: Present and Future Commercial Applications. Science 2013, 339, 535-539. [20] Vigolo, B.; Pénicaud, A.; Coulon, C.; Sauder, C.; Pailler, R.; Journet, C.; Bernier, P.; Poulin, P. Macroscopic Fibers and Ribbons of Oriented Carbon Nanotubes. Science 2000, 290, 1331-1334. [21] Ericson, L. M.; Fan, H.; Peng, H.; Davis, V. A.; Zhou, W.; Sulpizio, J.; Wang, Y.; Booker, R.; Vavro, J.; Guthy, C. et al. Macroscopic, Neat, Single-Walled Carbon Nanotube Fibers. Science 2004, 305, 1447-1450. [22] Zhang, X.; Li, Q.; Holesinger, T. G.; Arendt, P. N.; Huang, J.; Kirven, P. D.; Clapp, T. G.; DePaula, R. F.; Liao, X.; Zhao, Y. et al. Ultrastrong, Stiff, and Lightweight CarbonNanotube Fibers. Adv. Mater. 2007, 19, 4198-4201. [23] Behabtu, N.; Green, M. J.; Pasquali, M. Carbon Nanotube-Based Neat Fibers. Nano Today. 2008, 3, 25-34. [24] Behabtu, N.; Young, C. C.; Tsentalovich, D. E.; Kleinerman, O.; Wang, X.; Ma, A. W. K.; Bengio, E. A.; ter Waarbeek, R. F.; de Jong, J. J.; Hoogerwerf, R. E. et al. Strong, Light, Multifunctional Fibers of Carbon Nanotubes with Ultrahigh Conductivity. Science 2013, 339, 182-185. [25] Ryu, S.; Lee, P.; Chou, J. B.; Xu, R.; Zhao, R.; Hart, A. J.; Kim, S. G. Extremely Elastic Wearable Carbon Nanotube Fiber Strain Sensor for Monitoring of Human Motion. ACS nano 2015, 9, 5929-5936. [26] Podsiadlo, P.; Kaushik, A. K.; Arruda, E. M.; Waas, A. M.; Shim, B. S.; Xu, J.; Nandivada, H.; Pumplin, B. G.; Lahann, J.; Ramamoorthy, A. et al. Ultrastrong and Stiff 13 ACS Paragon Plus Environment

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Layered Polymer Nanocomposites. Science. 2007, 318, 80-83. [27] Paukner, C.; Koziol, K. K. K. Ultra-Pure Single Wall Carbon Nanotube Fibers Continuously Spun Without Promoter. Sci. Rep. 2014, 4, 03903. [28] Koziol, K.; Vilatela, J.; Moisala, A.; Motta, M.; Cunniff, P.; Sennett, M.; Windle, A.; High-Performance Carbon Nanotube Fiber. Science 2007, 318, 1891-1895. [29] Mercader, C.; Denis-Lutard, V.; Jestin, S.; Maugey, M.; Derré, A.; Zakri, C.; Poulin, P. Scalable Process for The Spinning of PVA-Carbon Nanotube Composite Fibers. J. Appl. Polym. Sci. 2012, 125, E191-E196. [30] Dalton, A. B.; Collins, S.; Muñoz, E.; Razal, J. M.; Ebron, V. H.; Ferraris, J. P.; Coleman, J. N.; Kim, B. G.; Baughman, R. H. Super-Tough Carbon-Nanotube Fibres. Nature 2002, 423, 703. [31] Dalton, A. B.; Collins, S.; Razal, J.; Munoz, E.; Ebron, V. H.; Kim, B. G.; Coleman, J. N.; Ferraris, J. P.; Baughman, R. H. Cotinuous Carbon Nanotube Composite Fibers: Properties, Potential Applications, and Problems. J. Mater. Chem. 2004, 14, 1-3. [32] Zhang, X. ; Liu, T. ; Sreekumar, T. V.; Kumar, S.; Hu, X.; Smith, K. Gel Spinning of PVA/SWNT Composite Fiber. Polymer 2004, 45, 8801-8807. [33] Wu, A. S.; Chou, T. W. Carbon Nanotube Fibers for Advanced Composites. Mater Today. 2012, 15, 302-310. [34] Lu, W.; Zu, M.; Byun, J. H.; Kim, B. S.; Chou, T. W. State of The Art of Carbon Nanotube Fibers: Opportunities and Challenges. Adv. Mater 2012, 24, 1805-1833. [35] Haddon, R. C.; Sippel, J.; Rinzler, A. G.; Papadimitrakopoulos, F. Purification and Separation of Carbon Nanotubes. Mater. Res. Bull. 2004, 29, 252–259. [36] Dastagir, T.; Xu, W.; Sinha, S.; Wu, H.; Cao, Y.; Yu, H. Tuning The Permeability of Permalloy Films for On-Chip Inductor Applications. Appl. Phys. Lett. 2010, 97, 162506. [37] Vaisman, L.; Wagner, H. D.; Marom, D. The Role of Surfactants in Dispersion of Carbon Nanotubes. Adv. Colloid. Interfac. 2006, 128, 37-46. 14 ACS Paragon Plus Environment

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Figure 1. a) Schematic of the arc-discharge setup for the fabrication process of SWNT/PNP nanopowder: graphite was used as electrodes with permalloy particles embedded in the cathode. b)-d), Low-magnification bright field TEM images of the as-prepared SWNT/PNP powders, which were heat treated in air at 400 °C for two hours and heat treated in H2 at 730 °C for two hours, respectively. b1)-d1) HRTEM images corresponding to b)-d). e) TGA curves of the powders.


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Figure 2. a) Wet spinning process of a SWNT/PNP/PVA fiber. b) Failed cross-sectional morphology and surface morphology of a SWNT/PNP/PVA fiber. c) Typical stress-strain curve of the fiber. d) Typical magnetization hysteresis loop of the fiber. e) The tensile strength and saturation magnetization of SWNT/PNP/PVA fibers as compared with the literature data for other magnetic polymer composites and fibers. The numbers in parentheses denote the reference number.


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Figure 3. a) Different types of fabric (dense or sparse) can be woven from the fabricated SWNT/PNP/PVA fibers by a weaving machine. b) A small magnet (1.5 g) was stuck on the fabric (0.5 g). c) Sketch of micro-strip line test method of the EMI attenuation: the signal line direction is indicated by the arrow. d) Scattering parameters were measured by a vector network analyzer. e) Comparison of the EMI attenuation performance between the SWNT/PNP/PVA fabric and the SWNT/MNP/PVA fabric. EMI attenuation, the ratio of the power loss (PLOSS) of the outgoing signal to the power of the incident signal (PIN), was calculated from scattering parameters.


ACS Nano

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Figure 4. Demonstration of electrical conductive property and magnetic field response of the SWNT/PNP/PVA fiber. A battery pack, a LED lamp, a small piece of copper plate and a SWNT/PNP/PVA fiber spring were connected in series to demonstrate the opening or closing of the circuit. a) and b) Top and side view of disconnected fiber and copper in the initial state showing the open state of the circuit. c) and d), Top and side view of a closed circuit by deformation of the fiber spring under a magnetic field (690 Gauss).


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Permalloy

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