Pristine carbon nanotube (CNT) fabric and Kevlar-reinforced CNT-silicone fabric were fabricated using a modified continuous floating catalyst chemical vapor deposition synthesis process. This scalable method produced fabrics measuring 25 cm × 90 cm, with thickness controlled via synthesis time. The CNT-based fabrics were flexible, electrically conductive, and reinforced with Kevlar yarn, fabric, or veil materials. Single-layer configurations exhibited electromagnetic interference (EMI) shielding effectiveness (SE) between 25 and 65 dB in the 8–12 GHz frequency range. Notably, multilayered assemblies of pristine CNT and CNT–silicone/Kevlar composite fabrics achieved an EMI SE of approximately 80 dB – one of the highest reported for CNT-based materials. These fabrics can be seamlessly incorporated into textiles and garments using conventional fabrication techniques. To demonstrate their practical applicability, an EMI shielding wallet was fabricated by stitching these fabrics together. Overall, this study presents high-performance EMI shielding fabrics with tunable specific shielding effectiveness ranging from 3700 to 70,000 dB·cm2/g, making them highly adaptable for various applications in defense, aerospace, communication, occupational safety, and industrial settings. Furthermore, the findings reinforce the notion that while electrical conductivity significantly influences EMI SE, it is not the sole determining factor.

The substitution of traditional copper power transmission cables with lightweight copper–carbon nanotube (Cu–CNT) composite fibers is critical for reducing the weight, fuel consumption, and CO2 emissions of automobiles and aircrafts. Such a replacement will also allow for lowering the transmission power loss in copper cables resulting in a decrease in coal and gas consumption, and ultimately diminishing the carbon footprint. In this work, we created a lightweight Cu–CNT composite fiber through a multistep scalable process, including spinning, densification, functionalization, and double-layer copper deposition. The characterization and testing of the fabricated fiber included surface morphology, electrical conductivity, mechanical strength, crystallinity, and ampacity (current density). The electrical conductivity of the resultant composite fiber was measured to be 0.5 × 106 S/m with an ampacity of 0.18 × 105 A/cm2. The copper-coated CNT fibers were 16 times lighter and 2.7 times stronger than copper wire, as they revealed a gravimetric density of 0.4 g/cm3 and a mechanical strength of 0.68 GPa, suggesting a great potential in future applications as lightweight power transmission cables.

The effects of dipole interactions on magnetic nanoparticle magnetization and relaxation dynamics were investigated using five nanoparticle (NP) systems with different surfactants, carrier liquids, size distributions, inter-particle spacing, and NP confinement. Dipole interactions were found to play a crucial role in modifying the blocking temperature behavior of the superparamagnetic nanoparticles, where stronger interactions were found to increase the blocking temperatures. Consequently, the blocking temperature of a densely packed nanoparticle system with stronger dipolar interactions was found to be substantially higher than those of the discrete nanoparticle systems. The frequencies of the dominant relaxation mechanisms were determined by magnetic susceptibility measurements in the frequency range of 100 Hz–7 GHz. The loss mechanisms were identified in terms of Brownian relaxation (1 kHz–10 kHz) and gyromagnetic resonance of Fe3O4 (~1.12 GHz). It was observed that the microwave absorption of the Fe3O4 nanoparticles depend on the local environment surrounding the NPs, as well as the long-range dipole–dipole interactions. These significant findings will be profoundly important in magnetic hyperthermia medical therapeutics and energy applications.

Conventional gloves partially insulate against heat transfer from a hot external environment. They also prevent metabolic heat generated by the human body from escaping. Thus, gloves are a source of heat buildup and heat stress in workers. Heat stress can lead to hyperthermia. Described herein is a glove that cools using a carbon nanotube (CNT) fabric micro-liner and forced convection from a fan. A cold sink is assumed to be located in the glove to cool the convection air. This glove is called an active textile glove. CNT fabric has high thermal conductivity in the plane of the fabric, low thermal conductivity through its thickness, and a large surface area for convection cooling. Thus, the active textile glove can transfer heat from the hand to cooler air in the environment. This paper simulates the performance of a CNT-cooled glove using simple theoretical heat transfer models. Cooling was also demonstrated by testing the glove using a hot plate. Forced convection was found to provide the greatest cooling effect, with it working in synergy with the CNT fabric which aids in spreading heat. CNT fabric also acts as a shield from environmental dangers. The fabric is flame resistant, attenuates radio frequency waves, and prevents smoke particles and toxic chemicals from entering the glove. Testing illustrates the shielding properties of CNT fabric.

Nanotube macroscale materials such as yarns, tapes, and sheets provide combinations of material properties that are unique relative to existing materials. Although nanotube sheet and yarn commercialization is still an emerging activity, these materials may become important in the future Business and Economics of societies. Therefore, this paper surveys current worldwide efforts toward manufacturing and commercialization of nanotube macroscale materials. The survey will help researchers, investors and economists consider how the new materials might be used in new applications and how the materials might spur economic development. Nanotube macroscale materials consist of yarn, tapes, and sheets, and exclude powdered forms of nanotubes used as filler materials. Both Carbon Nanotube (CNT) and Boron Nitride Nanotube (BNNT) materials are considered. It is anticipated that macroscale sheet and yarn with customizable properties will have broad applications. This paper is organized to provide ideas for possible areas of applications of nanotube yarn and sheet, followed by a survey of current commercialization efforts. Manufacturing barriers that must be overcome to push the development of nanotube macroscale materials toward large scale commercialization are also discussed. The paper also provides references for researchers and industry professionals who may want to further develop and put nanotube macroscale materials into their own applications.

The floating catalyst gas-phase pyrolysis method has been an important method to synthesize carbon nanotube sheet. Its advantage over other chemical vapor deposition methods is due to its continuous synthesis process and the potential for scaling up. Industries have already adopted this method to produce commercial products for various applications. But the synthesis process itself is time-consuming, and the high-temperature environment and use of explosive gases have hampered the practicality of daily-based activities for small-scale and research-oriented users. In this article, reactor design and several safety issues associated with this method will be addressed, and modifications will be discussed.

The development of synthesis techniques such as chemical vapor deposition (CVD) and floating catalyst CVD (FCCVD) has transformed CNTs from being property enhancing fillers in composites to structural materials of the future. These advanced synthesis techniques allow for ease in manufacturing of CNT sheets and their composites with other materials such as polymers and metals. Multipurpose CNT sheet composites find application in a variety of fields such as aerospace and energy storage. This chapter provides an insight into the development of the various techniques for manufacturing and processing of CNT sheets based on a review in the literature combined with our own experience. The “role reversal” in the development of high-strength CNT/polymer sheet composites, where the CNT is the majority phase, is discussed. CNT sheets are also excellent candidates for application as flexible, freestanding electrodes.

This work describes the design and fabrication of free-standing carbon nanotube-palladium (CNT-Pd) composite sheets for hydrogen gas sensing. The CNT-Pd composites were made by electroplating palladium onto a solvent-densified and oxygen plasma-treated CNT sheet. The latter was prepared using high purity CNTs drawn from a dense, vertically aligned array grown by chemical vapor deposition on silicon substrates. The CNT-Pd sheets were characterized by energy-dispersive spectroscopy, scanning electron microscopy, and X-ray diffraction. The amount of palladium in the composite was 16.5 wt % as measured via thermogravimetric analysis. Thin strips of the CNT-Pd sheets were assembled as chemiresistor sensors and tested for hydrogen gas detection. The sensors demonstrated a limit of detection of 0.1 mol % and displayed signal reversibility without the need for oxygen removal or heat treatment. A decrease in signal reversibility was observed after multiple exposure cycles; however, redensification with ethanol significantly restored the original reversibility. The sensor showed the Freundlich adsorption isotherm behavior when exposed to hydrogen. The material’s potential application toward a wearable, flexible sensor was demonstrated by integrating the chemiresistor onto a fabric material using hot-press processing and testing the composite for hydrogen sensitivity.

Carbon is the fourth most abundant element in the universe and is a versatile element to form advanced lightweight materials. In contrast, metals provide a different suite of properties including low cost, high conductivities, and scalability, while ceramics provide abrasion resistance and fire retardancy. An obstacle in materials science has been the inability to manufacture a material that integrates carbon materials and metals or ceramics together into a reproducible material whose properties can be customized to meet specific design requirements. One application is to produce electrically and thermally conductive nanotube hybrid sheet for use as performance fabrics and textiles. Thus, an area that will benefit from interdisciplinary research is developing a process to synthesize carbon nanotube hybrid materials. This chapter describes initial research into developing a continuous manufacturing process to integrate metal and ceramic nanoparticles (NPs) with carbon nanotubes (CNTs) and produce continuous materials (sheet, tapes, and yarn) whose properties can be customized based on the constituent metals.

The application of carbon nanotube (CNT) superfiber materials as lightweight, flexible, and durable RF antennas is explored through simulation, fabrication, and measurement. The fabrication of high-conductivity CNT thread is discussed, and a textile-integrated CNT bowtie antenna is explored through simulation and measurement. The fabrication of CNT sheet material is detailed, and an aperture-coupled CNT sheet patch antenna is measured, compared with a baseline copper patch antenna, and used to explore the effects of CNT orientation on the performance of a CNT sheet patch antenna. Postprocess treatments such as metal nanoparticle doping for enhanced conductivity and in situ atmospheric pressure plasma treatment for material functionalization are discussed, and the effects of these treatments on CNT antenna performance are explored through measurement.

In this investigation, the photothermal heating of superparamagnetic Fe 3 O 4 nanoparticles was carried out by irradiating with either 785[Formula: see text]nm or 808[Formula: see text]nm near infrared (NIR) lasers. The effects of nanoparticle configuration, arrangement, and surface coating on the photothermal heating behavior were investigated for different Fe 3 O 4 nanoparticle systems. Depending on the preparation method, Fe 3 O 4 nanoparticles with mean hydrodynamic diameter ranging from 30[Formula: see text]nm to 250[Formula: see text]nm were synthesized. Photothermal transduction efficiency is a measure of light to thermal energy conversion; the highest efficiency obtained was 56% by 785[Formula: see text]nm and 42% by 808[Formula: see text]nm light irradiation for poly(acrylic) acid (PAA) coated Fe 3 O 4 samples. With this conversion efficiency, the PAA-coated Fe 3 O 4 nanoparticles raised the solution temperature [Formula: see text] [Formula: see text]C above physiological temperature, which is sufficient for cancer therapeutics. Photothermal transduction efficiency was found to decrease as the particle hydrodynamic diameter increased. Nanoparticle absorption and scattering properties were found different due to surface modifications. UV-VIS-NIR absorption spectroscopy was carried out and results were analyzed using the Mie scattering theory. Experimental photothermal transduction efficiency was found to scale with the theoretical results for a particular wavelength. These results have significance in the design and development of the Fe 3 O 4 nanoparticle systems for effective cancer therapy with NIR light.

Industrialization (high rate manufacturing at a competitive cost) of nanotube superfiber materials could affect many products and improve economic conditions around the world. This will depend on improving and customizing the properties of nanotube materials and on scaling up the manufacturing to reduce the cost of nanotube sheets and yarn. This chapter presents ideas on how to scale up the manufacturing of nanotube materials based on the gas phase pyrolysis method, considering manufacturing on earth and in space, and with discussion of potential commercial applications of the materials.

Improved understanding of the science behind the nanotube synthesis process is driving continuous improvement of nanotube based yarn and sheet materials. Nanotube hybrid materials such as nanotubes and metals are being produced or assembled directly from the reactor which opens up a new arena of possibilities for the design of nanostructured materials. The cost of the materials will also be reduced due to higher yield manufacturing. Improved nanotube/hybrid materials are unique compared with many existing materials. Enticed by the potential commercial value of these materials, more industries are now beginning to supplement or replace their incumbent materials such as copper and composites with nanotube hybrid materials that are lighter, tougher, and carry more electrical current. This paper discusses the science and commercialization of nanotubes/hybrid materials along with a range of emerging applications that will benefit from the improved nanotube materials.

In this study, carbon nanotubes were synthesized at high temperature (1150–1500 °C) using the substrate-free gas phase pyrolysis method. The CNT sock morphology, CNT structure, impurity, process yield and growth efficiency at high temperatures were investigated. It was found that the CNTs transform from single-walled to multi-walled nanotubes at elevated temperature. The amount of amorphous impurities increases with higher temperature, possibly due to an increased non-catalytic decomposition of hydrocarbons. However the CNT quality increases, as indicated by a higher Raman spectroscopy IG/ID ratio. The process yield increase by two folds at higher temperature (1500 °C) compared to a lower temperature (1200 °C), but the catalyst efficiency is highest at 1400 °C with 1 g Fe producing 5.1 g CNT. The calculated carbon conversion rate is lower than 4%. The CNT growth is not limited by the availability of carbon around the catalyst, instead of by the availability of active catalyst particles. Based on a pristine CNT sheet, the measured electrical conductivity is highest at 1400 °C, due to a balance between impurities and CNT quality. The tensile strength of the CNT sheet increases with the temperature, possibly because of the "gluing" effect of the carbonaceous impurities.

Carbon nanotube (CNT) sock formation is required for the continuous synthesis of CNT thread or sheet using the gas phase pyrolysis method. Nanometer diameter CNTs form and are carried along the reactor tube by gas flow. During the flow, the CNT stick to each other and form bundles of about 10–100 nm diameter. Coupling of the CNT bundles in the flow leads to the formation of a centimeter diameter CNT sock with a wall that is hundreds of nanometers thick. Understanding the multiscale phenomena of sock formation is vital for optimizing the CNT synthesis and manufacturing process. In this work, we present a multiscale model for the CNT bundle agglomeration inside a horizontal gas phase pyrolysis reactor. The interaction between CNT bundles was analyzed by representing the attraction forces between CNTs using a discrete phase modeling method. Flow in the synthesis reactor was studied using a computational fluid dynamics (CFD) technique with multiphase flow analysis. A model was proposed to represent the coupling between CNT bundles and the gas flow. The effect of different CNT bundles on the agglomeration phenomenon was analyzed. The modeling results were also compared with experimental observations.

Electrowetting is well-established as a fluid manipulation technique in such areas as lab-on-a-chip, visible light optics, and displays, yet has seen far less implementation in the field of radio-frequency (RF) electronics and electromagnetics. This is primarily due to a lack of appropriate materials selection and control in these devices. Low loss RF conductive fluids such as room temperature liquid metals (i.e. Hg, EGaIn, Galinstan) are by far the leading choice of active material due to their superior electrical properties but require high actuating voltages due to their inherently high surface tensions (> 400 mN m(-1)) which often lead to dielectric breakdown. While the toxicity of Hg encourages the pursuit of non-toxic alternatives such as gallium alloys, the native surface oxide formation often prohibits reliable device functionality. Additionally, traditional electrowetting architectures rely on lossy electrode materials which degrade RF transmission efficiencies and result in non-reversible material diffusion at the electrode/liquid metal contact. In this work, we report on approaches to utilize liquid metals in electrowetting on dielectric (EWOD) devices that resolve all of these challenges by judicious choice of novel electrode materials, dielectric fluid, and device architecture. A functional RF device, namely an electromagnetic polarizer, is demonstrated that can be activated on demand through EWOD and provides an average signal attenuation of 12.91 dB in the on state and 1.46 dB in the off state over the range of 8-9.2 GHz, with a switching speed of about 12 ms. These results can be further extended to other RF applications such as tunable antennas, transmission lines, and switchable metasurfaces.

Effects of nanomaterial postprocess treatments on the RF performance of a variety of carbon nanotube patch antennas are explored through fabrication and measurement. A discussion of the physical and electrical mechanisms underpinning the results of these measurements is presented. The sparse application of metal nanoparticles to carbon nanotube sheet material is found to increase the peak realized gain ~1 dB compared to an untreated carbon nanotube sheet patch antenna. The functionalization of carbon nanotube sheet material through in situ atmospheric pressure plasma treatment is found to reduce the peak realized gain ~1.5 dB compared to an untreated carbon nanotube sheet patch antenna.

Multifunctional smart composites (MSCs) are materials that combine the good electrical and thermal conductivity, high tensile and shear strength, good impact toughness, and high stiffness properties of metals; the light weight and corrosion resistance properties of composites; and the sensing or actuation properties of smart materials. The basic concept for MSCs was first conceived by Daniel Inman and others about 25 years ago. Current laminated carbon and glass fiber polymeric composite materials have high tensile strength and are light in weight, but they still lack good electrical and thermal conductivity, and they are sensitive to delamination. Carbon nanotube yarn and sheets are lightweight, electrically and thermally conductive materials that can be integrated into laminated composite materials to form MSCs. This paper describes the manufacturing of high quality carbon nanotube yarn and sheet used to form MSCs, and integrating the nanotube yarn and sheet into composites at low volume fractions. Various up and coming technical applications of MSCs are discussed including composite toughening for impact and delamination resistance; structural health monitoring; and structural power conduction. The global carbon nanotube overall market size is estimated to grow from $2 Billion in 2015 to $5 Billion by 2020 at a CAGR of 20%. Nanotube yarn and sheet products are predicted to be used in aircraft, wind machines, automobiles, electric machines, textiles, acoustic attenuators, light absorption, electrical wire, sporting equipment, tires, athletic apparel, thermoelectric devices, biomedical devices, lightweight transformers, and electromagnets. In the future, due to the high maximum current density of nanotube conductors, nanotube electromagnetic devices may also become competitive with traditional smart materials in terms of power density.

Electrowetting and electrocapillarity of liquid metals have a long history, and a recent explosion of renewed interest. Liquid metals have electromagnetic properties and surface tensions (>500 mN/m) that enable new forms of reconfigurable devices. However, the only nontoxic option, gallium alloys, suffer from immediate formation of a semirigid surface oxide. Although acids or electrochemical reduction can remove this oxide, these approaches surround the gallium alloy in a fluid that is also electrically conducting, diminishing electromagnetic effectiveness and precluding electrowetting actuation. Reported here are acidified siloxanes that remove and prevent oxide formation. Importantly, the siloxane oil associatively incorporates hydrochloric or hydrobromic acids, is electrically insulating, is chemically stable, removes etching byproducts (including water), and allows robust electrowetting. This work opens up new opportunities for liquid metal reconfiguration, and is of fundamental interest due to the unexpected chemical stability of the acidified siloxanes and their application to other materials and surfaces.

Nanoparticle mediated photothermal ablation of cancerous tissue shows promising results and applicability as a highly efficacious treatment method. As a majority of the photothermal work has been conducted with minimal attenuation of the laser before reaching the nanoparticles within surface seeded tumors in-vivo or through buffered media in-vitro, it is important to understand the effects of greater laser attenuation on photothermal efficacy mediated by changes in the scattering and absorption of the laser. Photothermal efficacy using a near infrared (NIR) 785 nm laser irradiating polystyrene (PS) stabilized magnetite (Fe3O4) nanoparticles (PS-Fe3O4) is examined on MDA-MB-231 human mammary gland adenocarcinoma in-vitro. Agarose gel columns of various heights were created to simulate soft tissue and subsequently used for NIR laser attenuation. Polystyrene was found to significantly improve magnetite nanoparticle stability in serum containing media and modified Hank's Balanced Salt Solution and was able to induce significant hyperthermic ablation at mass concentrations which also did not elicit significant innate toxicity. Furthermore it was found that the polystyrene coating significantly reduced innate toxicity over 48 h compared to uncoated magnetite. Agar gel layers provided similar optical attenuation in the NIR region to skin and prostate.