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Natural Fiber Welding (NFW) is an Ionic Liquids (IL) based engineering process that can manipulate biopolymer matrices without destroying their underlying structure. It can be used to incorporate functional materials into the biopolymer matrix. In this study, we evaluate how NFW can be used to improve the thermal stability of natural textile fibers. First, a variety of synthesized and/or commercially available flame-retardant micro/nanomaterials are welded onto the surface of the fibers. Then, using thermogravimetric (TG) analysis, we demonstrate how each coating can enhance the thermal stability of the textile yarn. In some cases, thermal stability improves by as much as 25 °C, primarily through delays in the onset of thermal decomposition and increased char yield. Our data reveal strong potential for NFW to be used to deliver fiber-welded textile yarns with improved thermal stability.

Ionic liquids (IL) have been shown to be effective solvents for the dissolution of a wide variety of natural polymers, and new materials can be created from these natural feedstocks by processes that involve their full dissolution and subsequent reconstitution. Yet, the dissolution and reconstitution processes eliminates the native polymer structure often resulting in materials with significantly degraded physical properties when compared to the native material. However, if only the surface layers of these natural materials are mobilized through an ionic liquid facilitated process called Natural Fiber Welding (NFW), the underlying material retains its native character and mechanical properties while still allowing for significant material modification. Furthermore, the addition of functional materials (e.g. magnetic, optical, conductive) into the IL welding solution, allows for these substances to be entrained in and on the surface of the substrate imparting unique properties to the natural materials. In this work metallic nanoparticles were synthesized in linen powders by the process of incipient wetness impregnation. The linen containing nanoparticles were added to an IL and then welded to the surface of a natural polymer substrate (e.g., cotton yarn) via NFW. The morphology of the welded materials and the distribution of nanoparticles was characterized with TEM, SEM, and fluorescent imagery. Raman and infrared spectroscopies were used to evaluate the impact of the nanomaterials on the spectroscopic properties of the biocomposites, and atomic force microscopy and tensile strength testing were used to evaluate the mechanical properties of prepared composites. Using a variety of magnetic measurement techniques, we explored how nanoparticle composition and structure relate to each systems observed magnetic properties, and how some show nanomagnetic behavior at low temperature. Overall, the prepared composites maintained many of the attractive properties of the native substrates, while still exhibiting the functional properties of the entrained materials.

Throughout history humankind has exploited the remarkable properties of natural polymers such as silk and cellulose. In modern times, these natural materials still possess properties that rival the most advanced synthetic polymers. Recent work has shown ionic liquids (IL) to be effective solvents for the dissolution of a wide variety of natural polymers, and new materials can be created from these natural feedstocks by processes that involve their full dissolution and subsequent reconstitution. However, many reports show that the dissolution and reconstitution processes eliminate the native polymer structure, often with negative consequences to the physical properties of the resulting materials. Alternatively, if only the surface layers of these natural materials are mobilized through an ionic liquid facilitated process called Natural Fiber Welding (NFW), the underlying material retains its native character and mechanical properties while still allowing for significant material modification. Furthermore, the addition of functional materials (e.g. magnetic, conductive, antimicrobial) into the IL welding solution, allows for these substances to be entrained in and on the surface of the substrate imparting unique properties to the natural materials. Our group has endeavored to utilize NFW to modify natural materials to introduce novel functionalities. This work has encompassed the incorporation of a wide variety of polymeric, organic and inorganic materials into natural fiber matrices. Through the introduction of the appropriate materials we have been able to impart capacitive, conductive, catalytic, magnetic, optical, antimicrobial, and/or fire retardant functionalites into natural polymeric materials. In this presentation we will show our most recent efforts utilizing NFW to prepare novel functional natural materials.

We will present data for experiments that probe structure and dynamics at ionic liquid (IL) and ionic liquid-based (IL-based) systems with electrode interfaces. IL-based electrolytes have been investigated for applications ranging from energy conversion devices (e.g., capacitors, batteries, fuel cells, and solar cells) to sensors. Fundamental characterizations of IL-based electrolyte/electrode systems can contribute toward engineered progress for these enterprises since adsorbed species and their associated interfacial dynamics play critical roles in determining device efficiencies. Our studies utilize surface enhanced infrared absorption (SEIRA) spectroscopy. In particular, we demonstrate hyperspectral imaging at an attenuated total reflectance crystal that has been modified with a nanostructured gold electrode. Imaging experiments characterize interfacial structure and dynamics between several ionic liquid media (compositions) at the electrode surface simultaneously during electrochemical perturbation. Our initial spectral imaging studies explore ILs composed of imidazolium-based cations with alkylsulfate, tetrafluoroborate, thiocyanate, dicyanamide, and bis(trifluoromethylsulfonyl)imide anions.

Natural fiber welding (NFW) is a process that uses controlled amounts of ionic liquid and molecular co-solvent(s) to swell and mobilize portions of a natural polymer substrate. By carefully selecting factors controlling NFW such as time, temperature and solvent system composition, partial dissolution occurs, mobilizing and redistributing only a small portion of the natural polymer and leaving much of the underlying substrate intact. The NFW process results in fibers with a shell of dissolved/mobilized polymer, permanently adhered to both the outer diameter of the fiber and (depending on the extent of welding) to the surface of adjacent fibers. When polymeric and/or particulate materials are added during the NFW process, these substances can be integrated into the natural polymer matrix and modify its properties to include novel functionalities. In the present work we have applied the NFW process to the modification of natural polymer yarns. We have studied the processing conditions that impact the NFW of natural polymer yarns and the accompanied incorporation of functional materials (e.g., magnetic, conductive, and capacitive). We will discuss the preparation these functionalized yarns, and we will show data for their analysis using tensile testing, infrared spectroscopy, and scanning electron and con-focal fluorescence microscopies.

Applications of novel thin film electrodes are enabling the development of new commercial products ranging from in vivo biosensors, solar cells, and lithium-ion energy storage. A critical consideration that enables informed engineering of working devices is mass transport of electro-active species (EAS) and electrolytes within porous thin film electrodes. Initially we focus on the fabrication and characterization of transport within thin film electrodes fabricated from titanium dioxide, hydrogen titantate nanotubes, and zinc oxide via a sol-gel method. Characterization data for films deposited on indium tin oxide coated glass slides by doctor blade techniques are also discussed and include bright field microscopy, powder x-ray diffraction and, mass transport properties as investigated by cyclic voltammetry. Additionally we will discuss the creation and characterization of graphene nanosheets via the reduction of graphite oxide.

The utilization of ionic liquids (ILs) for future electrochemical applications shows great promise. Recently ILs have been investigated for many electrochemical systems however, further characterization and development of ILs remains to be accomplished before they are applied to devices such as batteries, capacitors, and fuel cells. For example, data that yield understanding of the interfacial structure and dynamics of ILs at electrode surfaces are vital since these interactions ultimately allude to electrochemical device efficiency. We will present data from time resolved (TRS) FTIR spectroscopy coupled with cyclic voltammetry as a means to characterize interfaces between IL-based electrolytes and metal electrode surfaces.

Natural fiber welding (NFW) is a method whereby solvent blends and process conditions are tailored to selectively swell and mobilize the biopolymers of fibrous, natural materials for functional (chemical and physical) modification.1-4 For example, careful control of solvent to substrate ratio, solvent composition (efficacy), as well as the time, temperature, pressure, and location of solvent exposure results in robust composites composed of fibrous substrates that are fused without glues or resins. The biopolymers within the cores of individual fibers may be demonstrated to retain their native structures and thus functionalities. In addition to unique fiber blends, other materials such as conductive carbons, magnets, fire retardants, et cetera may be incorporated during processing to yield highly functional composites that are sustainably produced and exhibit low embodied energy. In this presentation, we will discuss NFW processes to create flexible carbon-containing yarns for wearable supercapacitor applications. In particular, repeatable, scalable processes that generate composites that perform on par with similar state of the art devices reported in the literature. Given that these composites are based on truly ‘green’ cellulosic and lignocellulosic substrates (cotton and bamboo) and utilizing a nonfluorinated binder (cellulose from cotton), we believe this to be a significant breakthrough for the prospects of wearable energy storage.5-8 In addition, we will discuss the prospects for large scale nonwoven bio-based electrodes produced from inexpensive agricultural wastes and suitable for any number of important applications (e.g., filtration of pollutants from air and water). Acknowledgements: Portions of this work were funded by the Air Force Office of Scientific Research. Any opinions, findings, conclusions or recommendations expressed in the material are those of the authors and do not necessarily reflect the views of the U.S Navy or U.S Air Force. K. Jost acknowledges support from the DoD National Defense Science and Engineering Graduate (NDSEG) Fellowship. References: (1) L. M. Haverhals, W. M.Reichert, H. C. De Long, P. C. Trulove, Macromol. Mater. Eng., 2010, 295, 425-430. (2) L. M. Haverhals, H. M. Sulpizio, Z. A. Fayos, M. A. Trulove, W. M. Reichert, M. P. Foley, H. C. De Long, P. C. Trulove, ECS Transactions, 2010, 33, 79-90. (3) L. M. Haverhals, H. M. Sulpizio, Z. A. Fayos, M. A. Trulove, W. M. Reichert, M. P. Foley, H. C. De Long, P. C. Trulove, Cellulose, 2012, 19, 13-22. (4) L. M. Haverhals, L. M. Nevin, M. P. Foley, E. K. Brown, H. C. De Long, P. C Trulove, Chem. Commun., 2012, 48, 6417-6419. (5) Simon, P. & Gogotsi, Y. Nature Materials, 2009, 7, 845-854; (6) Jost, K. et al. Energy and Environmental Science 2011, 4, 5060-5067. (7) Jost, K. et al. Energ Environ Sci., 2013, 6, 2698–2705. (8) K. Jost, D. P. Durkin, L. M. Haverhals, E. K. Brown, M. Langenstein, H. C. De Long, P. C. Trulove, Y. Gogotsi, G. Dion, Adv. Energy Mater., 2015, 5, 1401286.

Ionic liquids (ILs) are potentially ‘game changing’ electrolytes for energy conversion applications such as capacitors [i] ,[ii] , batteries [iii] ,[iv] , fuel cells [v] ,[vi] , and solar cells. [vii] ,[viii] Significant progress has been made towards utilizing these remarkably adaptable materials for specific applications however, much work remains to generate technologically and economically relevant devices and processes.[ix] Characterizations of interfaces between IL-based electrolyte/electrode systems are crucial to continued development for these enterprises. In specific, detailed descriptions and understanding of structure and dynamics at electrolyte/electrode interfaces are necessary to realize engineered progress because device efficiencies are often largely determined by processes that occur at the interface. [x] ,[xi] Our presentation will focus on initial efforts to employ spectroscopic techniques that characterize interfacial structure and dynamics between ionic liquid media and electrode surfaces during simultaneous electrochemical perturbation. In specific, we will present surface enhanced infrared absorption (SEIRA) spectroscopy data for ILs composed of imidazolium-based cations with bis(trifluoromethylsulfonyl)imide anions at nanostructured noble metal electrodes (i.e, Au). [i]. T. Sato, G. Masuda, K. Takagi, Electrochim. Acta, 2004, 49, 3603-3611. [ii]. A. Orita, K. Kamijima, M. Yoshida, J. Power Sources, 2010, 195, 7471-7479. [iii]. A. S. Best, A. I. Bhatt, A. F. Hollenkamp, J. Electrochem. Soc., 2010, 157, A903-A911. [iv]. J.-K. Kima, A. Matica, J.-H. Ahnb, P. Jacobsson, J. Power Sources, 2010, 195, 7639-7643. [v]. S.-Y. Lee, A. Ogawa, M. Kanno, H. Nakamoto, T. Yasuda, M. Watanabe, J. Am. Chem. Soc., 2010, 132, 9764-9773. [vi]. M. Guo, J. Fang, H. Xu, W. Li, X. Lu, C. Lan, K. Li, J. Membr. Sci., 2010, 362, 97-104. [vii]. P. K. Singh, N. A. Jadhav, S. K. Mishra, U. P. Singh, B. Bhattacharya, Ionics, 2010, 16, 645-648. [viii]. C.-P. Lee, P.-Y. Chen, R. Vittal, K.-C. Ho, J. Mater. Chem., 2010, 20, 2356-2361. [ix]. M. Armand, F. Endres, D. R. MacFarlane, H. Ohno, B. Scrosati, Nature Materials, 2009, 8, 621-629. [x]. A. J. Bard, L. R. Faulkner, Electrochemical Methods: Fundamentals and Applications, 2nd ed., 2002, John Wiley & Sons, Inc., New York, NY. [xi]. M. Yoshida, A. Yamakata, K. Takanabe, J. Kubota, M. Osawa, K. Domen, J. Am. Chem. Soc., 2009, 131, 13218-13219.

The utilization of ionic liquids (ILs) for future electrochemical applications shows great promise. Recently ILs have been investigated for many electrochemical systems however, further characterization and development of ILs remains to be done before they are applied to devices such as batteries, capacitors, and fuel cells. For example, data that yield understanding of the interfacial structure and dynamics of ILs at electrode surfaces are vital since these interactions ultimately allude to electrochemical device efficiency. We will present time resolved (TRS) FTIR spectroscopy data as a means to characterize IL-based electrolytes. In particular, we will exhibit two modes of TRS: step scanning and rapid scanning during simultaneous electrochemical perturbation to better understand IL interactions at metal electrode surfaces.

Ionic liquids (IL) have been the focus of materials research for some time due to their unique physical and chemical properties. Of significant interest is their ability to solubilize biopolymers such as cellulose, chitin, keratin, and silk. However, full dissolution and regeneration using IL solvents often results in biomaterials with inferior properties compared to the native material. When natural substrates are only partially dissolved and regenerated through a process called Natural Fiber Welding (NFW), much of the native biomaterial structure can be maintained while still opening up the outermost portion of fibers so that the physical and chemical properties may be manipulated and/or modified. Furthermore, if functional materials (e.g. magnetic, conductive, capacitive, antimicrobial) are present in the IL-welding solution, these materials may be entrained in and on the surface of the fiber substrate. In the present work we will discuss the spatially controlled application of the NFW process and how this can be used to generated novel conductive and capacitive structures.

Development of novel thin film electrodes may enable new commercial products ranging from in vivo biosensors to solar cells. A critical consideration that assists the engineering of working devices is mass transport of electro-active species and solvent/electrolytes within porous thin film electrodes. Our presentation will focus on the fabrication and characterization of transport within thin film electrodes fabricated from titanium dioxide nanospheres, nanorods and nanotubes via sol-gel methods. We will present initial characterization data for films deposited on indium tin oxide coated glass slides by doctor blade techniques. Results include bright field and phase microscopy characterizations that probe the pore structure, surface morphology, and that yield physical dimensions of the films. Electron microscopy data will be presented that characterize particle dimensions and morphological differences resulting from multiple processing procedures. Powder x-ray diffraction data will be presented that investigate the crystal structure of the semiconducting films. Finally, mass transport properties as investigated by cyclic voltammetric techniques will be presented. Results will be correlated with fabrication techniques and associated material types and morphologies.

Certain ionic liquids (ILs) are known to be efficient solvents for biopolymers, in particular for cellulosic and silk based materials1. The ionic liquid solvent efficiency is strongly impacted by the presence of both impurities (e.g., water, residual reagents) and intentional additives (e.g., co-solvents or diluents)3,4. Natural fiber welding (NFW), the process of controlled partial dissolution and regeneration of biopolymers,5-7 is also affected by the presence of impurities and additives8. In this work we investigate the impact of impurities and additives on NFW. The extent of NFW was characterized by x-ray diffraction, ATR-IR, SEM, and mechanical property testing. These data are correlated with solvent physical properties, such as viscosity, density, and surface tension, as well as with solvent properties as indicated by their Kamlet-Taft parameters. For some of the systems investigated, there is a maximum solvent composition where polar aprotic solvents in conjunction with IL are more efficient at NFW than the IL alone. Surprisingly, this composition occurs when the mole ratio of IL to solvent is less than one to one. Understanding the factors that influence welding in these systems allows for greater control over the NFW process and facilitates the formation of functional biopolymer composite materials. References Swatloski, R. P.; Spear, S. K.; Holbrey, J. D.; Rogers, R. D. J. Am Chem Soc, 2002, 124, 4974. Phillips, D. M.; Drummy, L. F.; Conrady, D. G.; Fox, D. M.; Naik, R. R.; Stone, M. O.; Trulove, P. C.; De Long, H. C.; Mantz, R. A. J Am Chem Soc., 2004, 126, 14350. Rinaldi, R. Chem. Commun., 2011, 47, 511. Mazza, M.; Catana, D. A.; Vaca-Garcia, C.; Cecutti, C. Cellulose, 2009, 16, 207. Haverhals, L. M.; Reichert, W. M.; De Long, H. C.; Trulove, P. C. Cellulose, 2010, 2985, 425. Haverhals, L. M.; Sulpizio, H. M.; Fayos, Z. A.; Trulove, M. A.; Reichert, W. M.; Foley, M. P.; De Long, H. C.; Trulove, P. C.Cellulose, 2012, 19, 13. Haverhals, L. M.; Nevin, L. M.; Foley, M. P.; Brown, E. K.; De Long, H. C.; Trulove, P. C. Chem.Commun., 2012, 48, 6417. Haverhals, L. M.; Brown, E. K.; Foley, M. P.; De Long, H.; Trulove P. ECS Trans, 2012, 50, 6

As excellent solvents for cellulose and silk, certain ionic liquids (ILs), such as 1-ethyl-3-methylimidazolium acetate (EMIAc),1,2 can be used for biopolymer modification and manipulation. Full dissolution and regeneration using IL solvents often results in biomaterials with inferior properties compared to the native material. When natural substrates are only partially dissolved and regenerated through a process we call Natural Fiber Welding (NFW), much of the native biomaterial structure can be maintained while still allowing for significant material modification. NFW enables the structural modification of the surface and incorporation of functional materials through the binding capability of the portion of dissolved biopolymer3-5. In the present work we have employed a laser as the heat source to initiate partial dissolution of a cellulose substrate causing NFW in a spatially-specific manner. By using a non-solvent for cellulose (e.g., water) with the ionic liquid as a means of inhibiting the dissolution process, heat becomes the controlling factor necessary to obtain significant biopolymer dissolution and mobilization. A CO2 laser was used to raster a specific pattern onto a cellulosic paper substrate coated with IL solution. Raster power, concentration of the ionic liquid and the number of laser passes affect the amount of heat absorbed into the biopolymer and the level of NFW. Through tensile testing, confocal microscopy, ATR-IR, and SEM imaging, the resulting modification of the biopolymers was characterized. References Swatloski, R. P.; Spear, S. K.; Holbrey, J. D.; Rogers, R. D. J. Am Chem Soc, 2002, 124, 4974. Phillips, D. M.; Drummy, L. F.; Conrady, D. G.; Fox, D. M.; Naik, R. R.; Stone, M. O.; Trulove, P. C.; De Long, H. C.; Mantz, R. A. J Am Chem Soc., 2004, 126, 14350. Haverhals, L. M.; Reichert, W. M.; De Long, H. C.; Trulove, P. C. Cellulose, 2010, 2985, 425. Haverhals, L. M.; Sulpizio, H. M.; Fayos, Z. A.; Trulove, M. A.; Reichert, W. M.; Foley, M. P.; De Long, H. C.; Trulove, P. C.Cellulose, 2012, 19, 13. Haverhals, L. M.; Nevin, L. M.; Foley, M. P.; Brown, E. K.; De Long, H. C.; Trulove, P. C. Chem.Commun., 2012, 48, 6417.

In this application, an ionic liquid (IL), specifically 1-ethyl-3-methylmidazolium acetate (EMIAc), well known for its ability to dissolve a variety of biopolymers1-3, is used in conjunction with molecular co-solvents to prepare biopolymer composite yarns by a process we call natural fiber welding (NFW). NFW uses controlled amounts of IL and a molecular co-solvent to swell and mobilize portions of the biopolymer substrate. By carefully selecting factors controlling NFW such as time, temperature and solvent system composition, partial dissolution occurs, mobilizing and redistributing only a small portion of the natural fibers and leaving much of the underlying substrate intact.4-7 This results in fibers with a shell of dissolved polymer, permanently adhered and hydrogen bonded to both the outer diameter of the fiber and (depending on the extent of welding) to the surface of adjacent fibers. With the addition of a small amount of biopolymer into the IL solution, a NFW composite yarn can be created with the pre-dissolved biopolymer acting as an additional binder. Different combinations of biopolymer binder and substrate take advantage of the functional and structural benefits of both biopolymers. Binder can also be used to facilitate incorporation of functional materials (e.g., magnetic, electronic, photonic) into the yarn fiber matrix. References Swatloski, R. P.; Spear, S. K.; Holbrey, J. D.; Rogers, R. D. J. Am Chem Soc, 2002, 124, 4974. Phillips, D. M.; Drummy, L. F.; Conrady, D. G.; Fox, D. M.; Naik, R. R.; Stone, M. O.; Trulove, P. C.; De Long, H. C.; Mantz, R. A. J Am Chem Soc., 2004, 126, 14350. Xie, H.; Zhang, S.; Li, S. Green Chem. , 2006, 8, 630. Haverhals, L. M.; Reichert, W. M.; De Long, H. C.; Trulove, P. C. Cellulose, 2010, 2985, 425. Haverhals, L. M.; Sulpizio, H. M.; Fayos, Z. A.; Trulove, M. A.; Reichert, W. M.; Foley, M. P.; De Long, H. C.; Trulove, P. C.Cellulose, 2012, 19, 13. Haverhals, L. M.; Nevin, L. M.; Foley, M. P.; Brown, E. K.; De Long, H. C.; Trulove, P. C. Chem.Commun., 2012, 48, 6417. Haverhals, L. M.; Brown, E. K.; Foley, M. P.; De Long, H.; Trulove P. ECS Trans, 2012, 50, 603.

In the past decade, ionic liquids (ILs) have been investigated as electrolytes for energy conversion applications such as capacitors [i] ,[ii] , batteries [iii] ,[iv] , fuel cells [v] ,[vi] , and solar cells. [vii] ,[viii] While significant progress has been made towards utilizing these remarkably adaptable materials for specific applications, much work remains to generate technologically and economically relevant devices and processes. Fundamental characterizations of IL-based electrolyte/electrode systems are crucial to continued development for these enterprises. [ix] In specific, detailed descriptions and understanding of electrolyte/electrode interfaces are prerequisites to engineered progress because adsorbed species and their associated interfacial dynamics play critical roles in determining device efficiencies. [x] ,[xi] Our initial studies focus on spectroscopic techniques such as surface enhanced infrared absorption (SEIRA) spectroscopy to characterize interfacial structure and dynamics between ionic liquid media and electrode surfaces during electrochemical perturbation. More specifically, we will discuss characterizations of ILs composed of imidazolium-based cations with alkylsulfate, tetrafluoroborate, thiocyanate, dicyanamide, and bis(trifluoromethylsulfonyl)imide anions at noble metal electrodes (i.e, Au). [i]. T. Sato, G. Masuda, K. Takagi, Electrochim. Acta, 2004, 49, 3603-3611. [ii]. A. Orita, K. Kamijima, M. Yoshida, J. Power Sources, 2010, 195, 7471-7479. [iii]. A. S. Best, A. I. Bhatt, A. F. Hollenkamp, J. Electrochem. Soc., 2010, 157, A903-A911. [iv]. J.-K. Kima, A. Matica, J.-H. Ahnb, P. Jacobsson, J. Power Sources, 2010, 195, 7639-7643. [v]. S.-Y. Lee, A. Ogawa, M. Kanno, H. Nakamoto, T. Yasuda, M. Watanabe, J. Am. Chem. Soc., 2010, 132, 9764-9773. [vi]. M. Guo, J. Fang, H. Xu, W. Li, X. Lu, C. Lan, K. Li, J. Membr. Sci., 2010, 362, 97-104. [vii]. P. K. Singh, N. A. Jadhav, S. K. Mishra, U. P. Singh, B. Bhattacharya, Ionics, 2010, 16, 645-648. [viii]. C.-P. Lee, P.-Y. Chen, R. Vittal, K.-C. Ho, J. Mater. Chem., 2010, 20, 2356-2361. [ix]. C. Aliaga, C. S. Santos, S. Baldelli, Phys. Chem. Chem. Phys., 2007, 9, 3683-3700. [x]. A. J. Bard, L. R. Faulkner, Electrochemical Methods: Fundamentals and Applications, 2nd ed., 2002, John Wiley & Sons, Inc., New York, NY. [xi]. M. Yoshida, A. Yamakata, K. Takanabe, J. Kubota, M. Osawa, K. Domen, J. Am. Chem. Soc., 2009, 131, 13218-13219.

This report presents a novel ionic liquid-based method for fabricating flexible double layer supercapacitor electrodes utilizing natural substrates. It also investigates the performance of these yarns knitted as fabrics, and with other cellulose-based fibers welded with carbon particles. Scanning electron microscopy, mechanical properties testing, conductivity and other electrochemical testing are performed to characterize both individual yarns and knitted devices. Natural fiber welding (NFW) is a process that uses controlled amounts of ionic liquids (ILs) and molecular co-solvents to selectively swell and mobilize biopolymers in fibrous, natural materials for functional (chemical and physical) modification.1-4 NFW processes control and minimize the amount of dissolution to fibrous natural substrates. By carefully regulating the ratio of solvent to substrate, solvent efficacy, time, temperature, pressure, location of solvent exposure, etc., hydrogen bonding networks are reconfigured and extended by only mobilizing the outer shell of individual fibers. The result is that fibers are essentially ‘welded’ together while the cores maintain their native states. In this work, the fiber welding process has been modified to incorporate carbon materials into the biopolymer matrix, delivering flexible carbon containing yarns for wearable supercapacitor applications. To determine whether the material is a viable candidate for wearable supercapacitors, the welded carbon-yarns are coated with polymer electrolyte, twisted with stainless steel yarn (current collector) and electrochemically tested in a symmetric configuration through cyclic voltammetry, galvanostatic cycling, and impedance spectroscopy. Electrochemical testing performed on samples randomly selected across the entire length of yarn electrodes (typically 10-20 ft in length) yielded 8-12 mF/cm, comparable with previously reported literature. However, when the cotton is twisted with steel prior to coating, the capacitance dramatically increased to 45 mF/cm. Fabrication can have a dramatic effect on the electrochemical performance. Because mechanical properties of the cellulose yarns play a crucial role when knitting these capacitive yarns into full fabrics, tensile testing of the yarns pre- and post- welding was conducted. With each yarn, an improved strength was observed at the expense of elasticity; viscose and linen showed the most notable increases in strength (107%, 78% respectively) and toughness (both 22%). Though many of the cotton yarn electrodes showed favorable electrochemical performance, none were machine-knittable. The linen, viscose, and bamboo yarn supercapacitors were successfully machine knitted at Drexel’s Shima Seiki Haute Tech Lab. We currently attribute this to the length of the fibers playing a role in flexibility and mechanical strength within the yarn. More work is currently underway to explain this process, and fabricate a welded cotton yarn that can be knitted. To date, we have demonstrated a coating process that is repeatable and scalable (coating hundreds of feet at a time), inexpensive, and delivers competitive performance to similar reports in the literature. Given that composites are constructed from a truly ‘green’ substrate (cotton, bamboo, etc.) and utilizing a nonfluorinated binder (cellulose from cotton), we believe this to be a major breakthrough for the prospects of wearable energy storage.5-7 Acknowledgements: Portions of this work were funded by the Air Force Office of Scientific Research. Any opinions, findings, conclusions or recommendations expressed in the material are those of the authors and do not necessarily reflect the views of the U.S Navy or U.S Air Force. K. Jost acknowledges support from the DoD National Defense Science and Engineering Graduate (NDSEG) Fellowship. References: (1) L. M. Haverhals, W. M.Reichert, H. C. De Long, P. C. Trulove, Macromol. Mater. Eng., 2010, 295, 425-430. (2) L. M. Haverhals, H. M. Sulpizio, Z. A. Fayos, M. A. Trulove, W. M. Reichert, M. P. Foley, H. C. De Long, P. C. Trulove, ECS Transactions, 2010, 33, 79-90. (3) L. M. Haverhals, H. M. Sulpizio, Z. A. Fayos, M. A. Trulove, W. M. Reichert, M. P. Foley, H. C. De Long, P. C. Trulove, Cellulose, 2012, 19, 13-22. (4) L. M. Haverhals, M. P. Foley, E. K. Brown, L. M. Nevin, D. M. Fox, H. C. De Long, P. C. Trulove, ECS Transactions, 2012, 50, 603-613.. (5) Simon, P. & Gogotsi, Y. Nature Materials 7 (2009) 845-854; (6) Jost, K. et al. Energy and Environmental Science 4, (2011) 5060-5067; (7) Jost, K. et al. Energ Environ Sci, 6 (2013) 2698–2705

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