NTI Research
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Item Enhancement of Electromagnetic Interference Shielding Effectiveness with Alignment of Spinnable Multiwalled Carbon Nanotubes(Pergamon-Elsevier Science Ltd, 2018-10-23) Lee, Duck Weon; Park, Jongwoo; Kim, Bum Joon; Kim, Hyunsoo; Choi, Changsoon; Baughman, Ray H.; Kim, Seon Jeong; Kim, Youn Tae; 0000-0001-5845-5137 (Baughman, RH); Baughman, Ray H.This research develops a unique material to attenuate electromagnetic interference (EMI) by using spinnable multiwalled carbon nanotubes (MWNTs) combined with bio-polydimethylsiloxane (PDMS) that contains BaTiO₃ (MBPBT). In particular, a plaid pattern, formed by the spinnable MWNTs, is very effective in attenuating the propagation of EM waves, which achieves over 20 dB at 8.2-12.4 GHz (X-band frequency range). This means that a filter type of the spinnable MWNTs is actively able to handle the directionality and movement of EMI propagation. In addition, the MBPBT is characterized by its strong mechanical advantage (bending radius 180 degrees).Item Orthogonal Pattern of Spinnable Multiwall Carbon Nanotubes for Electromagnetic Interference Shielding Effectiveness(Elsevier Ltd, 2019-05-022) Lee, D. W.; Kim, H.; Moon, J. H.; Jeong, J. -H; Sim, H. J.; Kim, B. J.; Hyeon, J. S.; Baughman, Ray H.; Kim, S. J.; 0000-0001-5845-5137 (Baughman, RH); Baughman, Ray H.The need for thin and lightweight electromagnetic interference shielding materials is rapidly increasing in several industries, such as aerospace and telecommunication. This research finds that a shielding material, which is developed by the orthogonal pattern of spinnable multiwall carbon nanotubes (MWNTs), is ultra-light weight, thin, and has a high shielding effectiveness (SE). An orthogonal pattern, generated by just alignment of the spinnable MWNTs without adding any support materials such as polymers, ceramics, and magnets demonstrates that it is possible to efficiently attenuate electromagnetic interference (EMI) in the X-band frequency range (8.2–12.4 GHz). EMI SE in the developed shielding material is about 19.2 dB with a specific shielding effectiveness (SSE)/t (thickness) value of 73,633 dB cm² g⁻¹ at a thickness of about 4.48 μm. In addition, absorption effectiveness in this shielding material is as high as 96.3%, which provides excellent ability to reduce the secondary damage by reflection. ©2019 Elsevier LtdItem Photothermal Bimorph Actuators with In-Built Cooler for Light Mills, Frequency Switches, and Soft Robots(Wiley-VCH Verlag) Li, J.; Zhang, Rui; Mou, L.; Jung de Andrade, Monica; Hu, X.; Yu, K.; Sun, J.; Jia, T.; Dou, Y.; Chen, H.; Fang, Shaoli; Qian, Dong; Liu, Z.; 295272933 (Qian, D); Zhang, Rui; Jung de Andrade, Monica; Fang, Shaoli; Qian, DongPhotothermal bimorph actuators are widely used for smart devices, which are generally operated in a room temperature environment, therefore a low temperature difference for actuation without deteriorating the performance is preferred. The strategy for the actuator is assembling a broadband-light absorption layer for volume expansion and an additional water evaporation layer for cooling and volume shrinkage on a passive layer. The response time and temperature-change-normalized bending speed under NIR, white, and blue light illumination are at the same level of high performance, fast photothermal actuators based on polymer or polymer composites. The classical beam theory and finite element simulations are also conducted to understand the actuation mechanism of the actuator. A new type of light mill is designed based on a wing-flapping mechanism and a light-modulated frequency switch. A fast-walking robot (with a speed of 26 mm s -1 ) and a fast-and-strong mechanical gripper with a large weight-lifting ratio (˜2142), respectively, are also demonstrated. ©2019 WILEY-VCH Verlag GmbH & Co. KGaA, WeinheimItem High-Performance Biscrolled MXene/Carbon Nanotube Yarn Supercapacitors(Wiley-VCH Verlag) Wang, Z.; Qin, S.; Seyedin, S.; Zhang, J.; Wang, J.; Levitt, A.; Li, Na; Haines, Carter; Ovalle-Robles, R.; Lei, W.; Gogotsi, Y.; Baughman, Ray H.; Razal, J. M.; 0000 0003 5232 4253 (Baughman, RH); 0000-0001-5845-5137 (Baughman, RH); Li, Na; Haines, Carter; Baughman, Ray H.Yarn-shaped supercapacitors (YSCs) once integrated into fabrics provide promising energy storage solutions to the increasing demand of wearable and portable electronics. In such device format, however, it is a challenge to achieve outstanding electrochemical performance without compromising flexibility. Here, MXene-based YSCs that exhibit both flexibility and superior energy storage performance by employing a biscrolling approach to create flexible yarns from highly delaminated and pseudocapacitive MXene sheets that are trapped within helical yarn corridors are reported. With specific capacitance and energy and power densities values exceeding those reported for any YSCs, this work illustrates that biscrolled MXene yarns can potentially provide the conformal energy solution for powering electronics beyond just the form factor of flexible YSCs.Item Harvesting Electrical Energy from Torsional Thermal Actuation Driven by Natural Convection(Nature Publishing Group) Kim, Shi Hyeong; Sim, Hyeon Jun; Hyeon, Jae Sang; Suh, Dongseok; Spinks, Geoffrey M.; Baughman, Ray H.; Kim, Seon Jeong; 0000-0001-5845-5137 (Baughman, RH); Baughman, Ray H.; Kim, Seon JeongThe development of practical, cost-effective systems for the conversion of low-grade waste heat to electrical energy is an important area of renewable energy research. We here demonstrate a thermal energy harvester that is driven by the small temperature fluctuations provided by natural convection. This harvester uses coiled yarn artificial muscles, comprising well-aligned shape memory polyurethane (SMPU) microfibers, to convert thermal energy to torsional mechanical energy, which is then electromagnetically converted to electrical energy. Temperature fluctuations in a yarn muscle, having a maximum hot-to- cold temperature difference of about 13 ⁰C, were used to spin a magnetic rotor to a peak torsional rotation speed of 3,000 rpm. The electromagnetic energy generator converted the torsional energy to electrical energy, thereby producing an oscillating output voltage of up to 0.81 V and peak power of 4 W/kg, based on SMPU mass.Item Magnetic Torsional Actuation of Carbon Nanotube Yarn Artificial Muscle(Royal Society of Chemistry) Lee, D. W.; Kim, S. H.; Kozlov, Mikhail E.; Lepró, Xavier; Baughman, Ray H.; Kim, S. J.; 0000 0003 5232 4253 (Baughman, RH); 0000-0002-0166-3127 (Lepró, X); 0000-0001-5845-5137 (Baughman, RH); Kozlov, Mikhail E.; Lepró, Xavier; Baughman, Ray H.Magnetically driven torsional actuation of a multiwalled carbon nanotube (MWNT) yarn was realized by first biscrolling NdFeB magnetic particles into helical yarn corridors to make a magnetic MWNT yarn. The actuating device comprised a pristineMWNT yarn that was connected to the magnetic MWNT yarn, with a paddle attached between these yarns. The application of a magnetic field reversibly drove torsional actuation of up to 80° within ∼0.67 seconds. This magnetic actuator was remotely powered, and its actuation stroke was the same when the muscle array was at 20 °C and at -100 °C.Item Multi-Physics Simulation of Metal Printing at Micro/Nanoscale Using Meniscus-Confined Electrodeposition: Effect of Nozzle Speed and Diameter(American Institute of Physics Inc, 2018-08-31) Morsali, Seyedreza; Daryadel, Soheil; Zhou, Zhong; Behroozfar, Ali; Baniasadi, Mahmoud; Moreno, Salvador; Qian, Dong; Minary-Jolandan, Majid; Morsali, Seyedreza; Daryadel, Soheil; Zhou, Zhong; Behroozfar, Ali; Baniasadi, Mahmoud; Moreno, Salvador; Qian, Dong; Minary-Jolandan, MajidMeniscus-confined electrodeposition (MCED) is a solution-based, room temperature process for 3D printing of metals at micro/nanoscale. In this process, a meniscus (liquid bridge or capillary) between a nozzle and a substrate governs the localized electrodeposition process, which involves multiple physics of electrodeposition, fluid dynamics, mass, and heat transfer. We have developed a multiphysics finite element (FE) model to investigate the effects of nozzle speed (v N) and nozzle diameter (D0) in the MCED process. The simulation results are validated with experimental data. Based on theoretical approach and experimental observation, the diameter of the deposited wire is in the range of 0.5-0.9 times of the nozzle diameter. The applicable range for vN for various nozzle diameters is computed. The results showed that the contribution of migration flux to total flux remains nearly constant (∼50%) for all values of pipette diameter in the range examined (100 nm-5 μm), whereas the contribution of diffusion and evaporation fluxes to total flux increase and decrease with the increasing pipette diameter, respectively. Results of this multiphysics study can be used to guide the experiment for optimal process conditions. © 2017 Author(s).Item Highly Stretchable Hybrid Nanomembrane Supercapacitors(2016-03-04) Kim, Keon Jung; Lee, Jae Ah (UT Dallas); Lima, Márcio D. (UT Dallas); Baughman, Ray H.; Kim, Seon Jeong; 0000 0003 5232 4253 (Baughman, RH); Baughman, Ray H.Supercapacitors that are lightweight, mechanically deformable (stretchable, flexible) and electrochemically stable have potential for various applications like portable, wearable, and implantable electronics. Here we demonstrate a stretchable and high-performing hybrid nanomembrane supercapacitor. The hybrid nanomembrane is prepared by vapour phase polymerization (VPP) based nanoscopic PEDOT coating on carbon nanotube sheets (CNS) transferred onto an elastomeric substrate to form a wavy structure. The resulting wavy structured hybrid nanomembrane based supercapacitor exhibits high electrochemical performance and mechanical stretchability, simultaneously. The high specific capacitances and energy density (82 F g⁻¹, 11 mF cm⁻², and 7.28 W h kg⁻¹ at 0% strain) are retained under large mechanical deformation (77 F g⁻¹ and 6.87 W h kg⁻¹ at a biaxial strain of 600%). Moreover, there is only <1% degradation of capacitance ratio after 1000 cycles stretching/releasing and bending/unbending. This high mechanical cyclic stability is shown even during stretching/releasing and bending/unbending measured by dynamic cyclic voltammetry (CV). These results suggest that our supercapacitor is valuable in a wide range of applications that require it to be electrochemically stable under large mechanical deformation, such as strain sensors, wearable electronics and biomedical devices.Item Bio-Inspired, Moisture-Powered Hybrid Carbon Nanotube Yarn MusclesKim, Shi Hyeong; Kwon, Cheong Hoon; Park, Karam; Mun, Tae Jin; Lepro, Xavier; Baughman, Ray H.; Spinks, Geoffrey M.; Kim, Seon Jeong; 0000 0003 5232 4253 (Baughman, RH); 0000-0002-0166-3127 (Lepró, X); Lepró, Xavier; Baughman, Ray H.Hygromorph artificial muscles are attractive as self-powered actuators driven by moisture from the ambient environment. Previously reported hygromorph muscles have been largely limited to bending or torsional motions or as tensile actuators with low work and energy densities. Herein, we developed a hybrid yarn artificial muscle with a unique coiled and wrinkled structure, which can be actuated by either changing relative humidity or contact with water. The muscle provides a large tensile stroke (up to 78%) and a high maximum gravimetric work capacity during contraction (2.17 kJ kg⁻¹), which is over 50 times that of the same weight human muscle and 5.5 times higher than for the same weight spider silk, which is the previous record holder for a moisture driven muscle. We demonstrate an automatic ventilation system that is operated by the tensile actuation of the hybrid muscles caused by dew condensing on the hybrid yarn. This self-powered humidity-controlled ventilation system could be adapted to automatically control the desired relative humidity of an enclosed space.Item Shape-Engineerable Composite Fibers and Their Supercapacitor Application(RSC Pub, 2016-01-12) Kim, Kang Min; Lee, Jae Ah ((UT Dallas); Sim, Hyeon Jun; Kim, Kyung-Ah; Jalili, Rouhollah; Spinks, Geoffrey M.; Kim, Seon JeongDue to excellent electrical and mechanical properties of carbon nano materials, it is of great interest to fabricate flexible, high conductive, and shape engineered carbon based fibers. As part of these approaches, hollow, twist, ribbon, and other various shapes of carbon based fibers have been researched for various functionality and application. In this paper, we suggest simple and effective method to control the fiber shape. We fabricate the three different shapes of hollow, twisted, and ribbon shaped fibers from wet spun giant graphene oxide (GGO)/single walled-nanotubes (SWNTs)/poly(vinyl alcohol) (PVA) gels. Each shaped fibers exhibit different mechanical properties. The average specific strengthes of the hollow, twist, and ribbon fibers presented here are 126.5, 106.9, and 38.0 MPa while strain are 9.3, 13.5, and 5%, respectively. Especially, the ribbon fiber shows high electrical conductivity (524 ± 64 S cm⁻¹) and areal capacitance (2.38 mF cm⁻²).Item Biothermal Sensing of a Torsional Artificial Muscle(Royal Soc Chemistry, 2016-01-25) Lee, Sung-Ho; Kim, Tae Hyeob; Lima, M©rcio D.; Baughman, Ray H.; Kim, Seon Jeong; 0000 0003 5232 4253 (Baughman, RH); Lima, M©rcio D.; Baughman, Ray H.Biomolecule responsive materials have been studied intensively for use in biomedical applications as smart systems because of their unique property of responding to specific biomolecules under mild conditions. However, these materials have some challenging drawbacks that limit further practical application, including their speed of response and mechanical properties, because most are based on hydrogels. Here, we present a fast, mechanically robust biscrolled twist-spun carbon nanotube yarn as a torsional artificial muscle through entrapping an enzyme linked to a thermally sensitive hydrogel, poly(N-isopropylacrylamide), utilizing the exothermic catalytic reaction of the enzyme. The induced rotation reached an equilibrated angle in less than 2 min under mild temperature conditions (25-37 ⁰C) while maintaining the mechanical properties originating from the carbon nanotubes. This biothermal sensing of a torsional artificial muscle offers a versatile platform for the recognition of various types of biomolecules by replacing the enzyme, because an exothermic reaction is a general property accompanying a biochemical transformation.Item Microwave Conductance of Aligned Multiwall Carbon Nanotube Textile Sheets(2014-12-30) Brown, Brian L.; Bykova, Julia S.; Howard, Austin R.; Zakhidov, Anvar A.; Shaner, Eric A.; Lee, Mark; Brown, Brian L.; Bykova, Julia S.; Howard, Austin R.; Zakhidov, Anvar A.; Lee, MarkMultiwall carbon nanotube (MWNT) sheets are a class of nanomaterial-based multifunctional textile with potentially useful microwave properties. To understand better the microwave electrodynamics, complex AC conductance measurements from 0.01 to 50 GHz were made on sheets of highly aligned MWNTs with the alignment texture both parallel and perpendicular to the microwave electric field polarization. In both orientations, the AC conductance is modeled to first order by a parallel frequency-independent conductance and capacitance with no inductive contribution. This is consistent with low-frequency diffusive Drude AC conduction up to 50 GHz, in contrast to the "universal disorder" AC conduction reported in many types of single-wall nanotube materials.Item Electron and Hole Polaron Accumulation in Low-Bandgap Ambipolar Donor-Acceptor Polymer Transistors Imaged by Infrared Microscopy(2014-12-08) Khatib, O.; Mueller, A. S.; Stinson, H. T.; Yuen, Jonathan D.; Heeger, A. J.; Basov, D. N.A resurgence in the use of the donor-acceptor approach in synthesizing conjugated polymers has resulted in a family of high-mobility ambipolar systems with exceptionally narrow energy bandgaps below 1 eV. The ability to transport both electrons and holes is critical for device applications such as organic light-emitting diodes and transistors. Infrared spectroscopy offers direct access to the low-energy excitations associated with injected charge carriers. Here we use a diffraction-limited IR microscope to probe the spectroscopic signatures of electron and hole injection in the conduction channel of an organic field-effect transistor based on an ambipolar DA polymer polydiketopyrrolopyrrole-benzobisthiadiazole. We observe distinct polaronic absorptions for both electrons and holes and spatially map the carrier distribution from the source to drain electrodes for both unipolar and ambipolar biasing regimes. For ambipolar device configurations, we observe the spatial evolution of hole-induced to electron-induced polaron absorptions throughout the transport path. Our work provides a platform for combined transport and infrared studies of organic semiconductors on micron length scales relevant to functional devices.Item A Simple/Green Process for the Preparation of Composite Carbon Nanotube Fibers/Yarns(2014-09-04) Rahy, Abdelaziz; Choudhury, Arup; Kim, Changheon; Ryu, Sungwoo; Hwang, Jaewon; Hong, Soon Hyung; Yang, Duck J.; Korea Center for Nanostructured Material Technology; Korea Advanced Institute of Science and TechnologyWe report a simple and green process to prepare poly(vinyl alcohol)/carbon nanotube (PVA/CNT) composite fibers having high mechanical properties. This process, an environmentally friendly one with no use of acid or hazardous solvent, produces the composite fibers utilizing a PVA layer pre-coated on a PET film. SEM micrographs indicated that the CNTs are well dispersed in the PVA matrix, and the diameter of the fiber is around 50 μm. Mechanical properties of the composite fiber treated at different thermal annealing conditions are also reported.Item Towards an Understanding of Structure-Nonlinearity Relationships in Triarylamine-based Push-Pull Electro-Optic Chromophores: The Influence of Substituent and Molecular Conformation on Molecular Hyperpolarizabilities(Royal Soc Chemistry, 2014-02-17) Wu, Jingbo; Wilson, Blake A.; Smith, Dennis W., Jr.; Nielsen, Steven O.; 2012052347 (Smith, DW); Smith, Dennis W., Jr.; Nielsen, Steven O.We calculated the second-order hyperpolarizability (beta) of a series of triarylamine (TAA) based donor-bridge-acceptor (D-π-A) push-pull type nonlinear optical (NLO) chromophores with different electron donor moieties and the same thiophene π-bridge and dicyanovinyl electron acceptor using a time-dependent Hartree-Fock (TDHF) approach within the software package MOPAC 2012. NLO chromophores with various quantities and positions of methoxy groups in the TAA donor moiety were investigated. The relationship between NLO properties and the electronic or geometric structures of the TAA donor subunit is discussed through the calculation results. Both substituent and conformational effects affect the delocalization of the nitrogen lone pair into the aryl rings, leading to a dramatic influence on the nonlinear optical properties. Introduction of methoxy groups at the ortho positions of the TAA moiety has a larger influence on the molecular hyperpolarizability and dipole moment than the introduction of methoxy group at the para or meta positions. Our calculation results demonstrate how to improve the NLO properties of TAA based chromophores while meeting practical device requirements.Item A New Catalyst-Embedded Hierarchical Air Electrode For High-Performance Li-O₂ Batteries(2013-06-05) Lim, H. -D; Song, H.; Gwon, H.; Park, K. -Y; Kim, J.; Bae, Y.; Kim, H.; Jung, S. -K; Kim, T.; Kim, Y. H.; Lepr©, Xavier; Ovalle-Robles, Raquel; Baughman, Ray H.; Kang, K.; 0000 0003 5232 4253 (Baughman, RH); Lepr©, Xavier; Ovalle-Robles, Raquel; Baughman, Ray H.The Li-O₂ battery holds great promise as an ultra-high-energy- density device. However, its limited rechargeability and low energy efficiency remain key barriers to its practical application. Herein, we demonstrate that the ideal electrode morphology design combined with effective catalyst decoration can enhance the rechargeability of the Li-O₂ battery over 100 cycles with full discharge and charge. An aligned carbon structure with a hierarchical micro-nano-mesh ensures facile accessibility of reaction products and provides the optimal catalytic conditions for the Pt catalyst. The new electrode is highly reversible even at the extremely high current rate of 2 A g⁻¹. Moreover, we observed clearly distinct morphologies of discharge products when the catalyst is used. The effect of catalysts on the cycle stability is discussed.Item Conductive Functional Biscrolled Polymer and Carbon Nanotube Yarns(2013-10-10) Kim, S. H.; Sim, H. J.; Shin, M. K.; Choi, A. Y.; Kim, Y. T.; Lima, Marcio D.; Baughman, Ray H.; Kim, S. J.; 0000 0003 5232 4253 (Baughman, RH); Lima, Marcio D.; Baughman, Ray H.Biscrolling aligned electrospun fiber (AEF) sheets and carbon nanotube (CNT) sheets were fabricated for conductive, functional yarns by a versatile dry composite method. Our biscrolling (twist-based spinning) method is based on spinnable polymer fiber sheets and spinnable CNT sheets unlike the previous biscrolling technique using unspinnable nanopowders and spinnable CNT sheets. The CNT sheet in composite yarns acted as effective electrical wires forming dual Archimedean multilayer rolled-up nanostructures. The weight percent of the electrospun polymer fibers in the composite yarns was over 98%, and the electrical conductivity values of the composite yarns was 3 orders higher than those of other non-conducting polymer/CNT composite fibers which were electrospun from polymer solutions containing similar loading of CNTs. We also demonstrate that biscrolled yarns having various structures can be fabricated from spinnable AEF sheets and spinnable CNT sheets.Item Superconductivity in an inhomogeneous bundle of metallic and semiconducting nanotubes(2013-09-06) Grigorenko, I.; Zakhidov, Anvar A.; 0000 0003 5287 0481 (Zakhidov, AA); Zakhidov, Anvar A.Using Bogoliubov-de Gennes formalism for inhomogeneous systems, we have studied superconducting properties of a bundle of packed carbon nanotubes, making a triangular lattice in the bundle's transverse cross-section. The bundle consists of a mixture of metallic and doped semiconducting nanotubes, which have different critical transition temperatures. We investigate how a spatially averaged superconducting order parameter and the critical transition temperature depend on the fraction of the doped semiconducting carbon nanotubes in the bundle. Our simulations suggest that the superconductivity in the bundle will be suppressed when the fraction of the doped semiconducting carbon nanotubes will be less than 0.5, which is the percolation threshold for a two-dimensional triangular lattice.Item A Carbon Nanotube-based Raman-imaging Immunoassay For Evaluating Tumor Targeting Ligands(Royal Society of Chemistry, 2014-04-16) Bajaj, Pooja; Mikoryak, Carole; Wang, Ruhung; Bushdiecker II, David K.; Memon, Pauras; Draper, Rockford K.; Dieckmann, Gregg R.; Pantano, Paul; Musselman, Inga H.; Pantano, Paul; Musselman, Inga H.Herein, we describe a versatile immunoassay that uses biotinylated single-walled carbon nanotubes (SWNTs) as a Raman label, avidin-biotin chemistry to link targeting ligands to the label, and confocal Raman microscopy to image whole cells. Using a breast tumor cell model, we demonstrate the usefulness of the method to assess membrane receptor/ligand systems by evaluating a monoclonal antibody, Her-66, known to target the Her2 receptors that are overexpressed on these cells. We present two-dimensional Raman images of the cellular distribution of the SWNT labels corresponding to the distribution of the Her2 receptors in different focal planes through the cell with validation of the method using immunofluorescence microscopy, demonstrating that the Her-66-SWNT complexes were targeted to Her2 cell receptors.;Item High Temperature Structural Transformations of Few Layer Graphene Nanoribbons Obtained By Unzipping Carbon Nanotubes(2013-11-11) Castillo-Martínez, Elizabeth; Carretero-González, Javier; Sovich, Justin; Lima, Márcio. D.; Alan G. MacDiarmid NanoTech InstituteMultilayer and few layer graphene nanoribbons produced by oxidative unzipping of carbon multiwalled carbon nanotubes (MWNT 10 > N > 5) and N ≤ 4 carbon few walled nanotubes (FWNT) were annealed at temperatures up to 1400 °C and the resulting carbon nanostructures were studied. Transmission electron microscopy imaging of the graphene nanoribbons annealed in bulk shows higher structural stability in larger width multilayer graphene nanoribbons than in narrow few layer nanoribbons. Fringes of dark and bright contrast along the edges of MLG indicate edge closure within the layers of the stacked graphene nanoribbons. On the other hand, narrow FLG nanoribbons fuse within each other or collapse when annealed leading to three different nanostructures: large area MLG plates several microns wide, graphitic onions of approximately 100 nm in diameter and nanocrystalline/amorphous composite particles.