The operational window of carbon nanotube electrical wires treated with strong acids and oxidants

Conventional metal wires suffer from a significant degradation or complete failure in their electrical performance, when subjected to harsh oxidizing environments, however wires constructed from Carbon Nanotubes (CNTs) have been found to actually improve in their electrical performance when subjected to these environments. These opposing reactions may provide new and interesting applications for CNT wires. Yet, before attempting to move to any real-world harsh environment applications, for the CNT wires, it is essential that this area of their operation be thoroughly examined. To investigate this, CNT wires were treated with multiple combinations of the strongest acids and halogens. The wires were then subjected to conductivity measurements, current carrying capacity tests, as well as Raman, microscopy and thermogravimetric analysis to enable the identification of both the limits of oxidative conductivity boosting and the onset of physical damage to the wires. These experiments have led to two main conclusions. Firstly, that CNT wires may operate effectively in harsh oxidizing environments where metal wires would easily fail and secondly, that the highest conductivity increase of the CNT wires can be achieved through a process of annealing, acetone and HCl purification followed by either H2O2 and HClO4 or Br2 treatment

Versatile Sarcosine Biosensing Schemes Utilizing Layer-by-Layer Construction of Carbon Nanotube-Chitosan Composite Films

Layer-by-layer composite films of carbon nanotubes (CNTs) within a chitosan matrix with sarcosine oxidase enzyme and capped with Nafion have been developed and optimized as a versatile 1st generation amperometric sarcosine biosensing platform that operates successfully both as an isolated sarcosine sensor as well as a functional component within a creatinine sensor. Accurate measurement of sarcosine in urine and creatinine in blood may help with early diagnosis of diseases such as prostate cancer and renal failure, respectively. In this study, each material within the film is systematically optimized toward sarcosine sensitivity, including a critical evaluation of different CNTs effect on sensing performance. Films featuring carboxylic acid–modified single–walled carbon nanotubes and strategic enzyme doping were shown to be most effective sarcosine sensing platforms, exhibiting excellent sensitivity (~0.5 μA/mM), a linear response (≤ 0.75 mM), fast response time (8 s), low limits of detection (~6 μM), as well as both continuous use stability (7 days) and effective shelf life (\u3e 12 days). Operation of the sarcosine sensor was demonstrated in a urine matrix, detecting sarcosine at physiologically relevant concentrations and successfully quantifying sarcosine-spiked urine samples with high percent recovery and low relative error. The sarcosine sensing platform was also adapted to a 1st generation creatinine biosensing scheme in which the sarcosine enzymatic reaction is critical to a trienzymatic cascade event. The creatinine sensor yielded sensitivity of ~0.6 μA/mM, similar sensing performance parameters to the sarcosine sensor, and was effectively operated in blood serum at physiologically relevant creatinine concentrations. The demonstrated functionality of these sensors in their respective biological fluids at physiological concentrations of the analyte species suggests potential clinical application as diagnostic tools

Electrical properties of carbon nanotube based fibers and their future use in electrical wiring

The production of continuous fibers made purely of carbon nanotubes has paved the way for new macro-scale applications which utilize the superior properties of individual carbon nanotubes. These wire-like macroscopic assemblies of carbon nanotubes were recognized to have a potential to be used in electrical wiring. Carbon nanotube wiring may be extremely light and mechanically stronger and more efficient in transferring high frequency signals than any conventional conducting material, being cost-effective simultaneously. However, transfer of the unique properties of individual CNTs to the macro-scale proves to be quite challenging. This Feature Article gives an overview of the potential of using carbon nanotube fibers as next generation wiring, state of the art developments in this field, and goals to be achieved before carbon nanotubes may be transformed into competitive products. Carbon nanotubes, with their unique properties, could make electrical conductors of unprecedented performance, which could revolutionize energy transport globally. Is it feasible to produce macroscopic conductors from nanoscale structures? This Feature Article presents both the most recent results of a highly promising research program in this area and the key challenges that need to be overcome. © 2014 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Piezoresistive Effect in Carbon Nanotube Fibers

The complex structure of the macroscopic assemblies of carbon nanotubes and variable intrinsic piezoresistivity of nanotubes themselves lead to highly interesting piezoresistive performance of this new type of conductive material. Here, we present an in-depth study of the piezoresistive effect in carbon nanotube fibers, <i>i.e.</i>, yarnlike assemblies made purely of aligned carbon nanotubes, which are expected to find applications as electrical and electronic materials. The resistivity changes of carbon nanotube fibers were measured on initial loading, through the elastic/plastic transition, on cyclic loading and on stress relaxation. The various regimes of stress/strain behavior were modeled using a standard linear solid model, which was modified with an additional element in series to account for the observed creep behavior. On the basis of the experimental and modeling results, the origin of piezoresistivity is discussed. An additional effect on the resistivity was found as the fiber was held under load which led to observations of the effect of humidity and the associated water adsorption level on the resistivity. We show that the equilibrium uptake of moisture leads to the decrease in gauge factor of the fiber decrease, <i>i.e.</i>, the reduction in the sensitivity of fiber resistivity to loading

Highly Conductive Carbon Nanotube-Thermoplastic Polyurethane Nanocomposite for Smart Clothing Applications and Beyond

The following paper presents a simple, inexpensive and scalable method of production of carbon nanotube-polyurethane elastomer composite. The new method enables the formation of fibers with 40% w/w of nanotubes in a polymer. Thanks to the 8 times higher content of nanotubes than previously reported for such composites, over an order of magnitude higher electrical conductivity is also observed. The composite fibers are highly elastic and both their electrical and mechanical properties may be easily controlled by changing the nanotubes content in the composite. It is shown that these composite fibers may be easily integrated with traditional textiles by sewing or ironing. However, taking into account their light-weight, high conductivity, flexibility and easiness of molding it may be expected that their potential applications are not limited to the smart textiles industry