Controlling the dynamic percolation of carbon nanotube based conductive polymer composites by addition of secondary nanofillers: The effect on electrical conductivity and tuneable sensing behaviour

In this paper, the electrical properties of ternary nanocomposites based on thermoplastic polyurethane (TPU) and multi-walled carbon nanotubes (MWCNTs) are studied. In particular two nanofillers - differing in shape and electrical properties - are used in conjunction with MWCNTs: an electrically conductive CB and an insulating needle-like nanoclay, sepiolite. The ternary nanocomposites were manufactured in a number of forms (extruded pellets, filaments and compression moulded films) and their morphological and electrical properties characterised as function of time and temperature. The presence of both secondary nanofillers is found to affect the formation of a percolating network of MWCNTs in TPU, inducing a reduced percolation threshold and tuneable strain sensing ability. These ternary nanocomposites can find application as conductive and multi-functional materials for flexible electronics, sensing films and fibres in smart textiles. (c) 2012 Elsevier Ltd. All rights reserved

Static and dynamic strain sensing using a polymer : carbon nanotube film strain sensor

The search for new multipoint, multidirectional strain sensing devices has received a new impetus since the discovery of carbon nanotubes. The excellent electrical, mechanical, and electromechanical properties of carbon nanotubes make them ideal candidates as primary materials in the design of this new generation of sensing devices. Carbon nanotube based strain sensors proposed so far include those based on individual carbon nanotubes for integration in nano or micro elecromechanical systems (NEMS/MEMS) [1], or carbon nanotube films consisting of spatially connected carbon nanotubes [2], carbon nanotube - polymer composites [3,4] for macroscale strain sensing. Carbon nanotube films have good strain sensing response and offer the possibility of multidirectional and multipoint strain sensing, but have poor performance due to weak interaction between carbon nanotubes. In addition, the carbon nanotube film sensor is extremely fragile and difficult to handle and install. We report here the static and dynamic strain sensing characteristics as well as temperature effects of a sandwich carbon nanotube - polymer sensor fabricated by infiltrating carbon nanotube films with polymer

Tuning Electrical Conductivity of CNT-PDMS Nanocomposites for Flexible Electronic Applications

This paper presents a study into the electrical conductivity of multi-wall carbon nanotube-polydimethylsiloxane (MWNT-PDMS) nanocomposite and their dependence on the filler concentration. It is observed that the electrical conductivity of the composites can be tailored by altering the filler concentration. Accordingly, the nanocomposites with filler weight ratio ranging from 1% to 8% were prepared and tested. Finally, the significance of results presented here for flexible pressure sensors and stretchable interconnects for electronic skin applications have been discussed

Characterizing the Conductivity and Enhancing the Piezoresistivity of Carbon Nanotube-Polymeric Thin Films.

The concept of lightweight design is widely employed for designing and constructing aerospace structures that can sustain extreme loads while also being fuel-efficient. Popular lightweight materials such as aluminum alloy and fiber-reinforced polymers (FRPs) possess outstanding mechanical properties, but their structural integrity requires constant assessment to ensure structural safety. Next-generation structural health monitoring systems for aerospace structures should be lightweight and integrated with the structure itself. In this study, a multi-walled carbon nanotube (MWCNT)-based polymer paint was developed to detect distributed damage in lightweight structures. The thin film's electromechanical properties were characterized via cyclic loading tests. Moreover, the thin film's bulk conductivity was characterized by finite element modeling

Highly reproducible, hysteresis-free, flexible strain sensors by inkjet printing of carbon nanotubes

In order to build upon the exceptional interest for flexible sensors based on carbon nanotube networks (CNNs), the field requires high device-to-device reproducibility. Inkjet printing has provided outstanding results for flexible ohmic sensors in terms of reproducibility of their resistance. However, the reproducibility of the sensitivity, the most critical parameter for sensing application, has been only marginally assessed. In the present paper, CNN based resistive strain sensors fabricated by inkjet-printing on flexible Ethylene Tetrafluoroethylene (EFTE) sheets are presented. The variability on the device initial resistance is studied for 5 different batches of sensors from 3 to 72 devices each. The variability ranges between 8.4% and 43% depending on the size of the batches, with a 20% average. An 8-device batch with 15% variability on initial resistance is further studied for variability on the strain and thermal sensitivity. Standard deviation values are found to be as low as 16% on the strain sensitivity and 8% on the temperature sensitivity. Moreover, the devices are hysteresis free, a rare achievement for CNT strain sensors on plastics

Facile fabrication of stretchable Ag nanowire/polyurethane electrodes using high intensity pulsed light

Silver nanowires (AgNWs) have emerged as a promising nanomaterial for next generation stretchable electronics. However, until now, the fabrication of AgNW-based components has been hampered by complex and time-consuming steps. Here, we introduce a facile, fast, and one-step methodology for the fabrication of highly conductive and stretchable AgNW/polyurethane (PU) composite electrodes based on a high-intensity pulsed light (HIPL) technique. HIPL simultaneously improved wire-wire junction conductivity and wire-substrate adhesion at room temperature and in air within 50 mu s, omitting the complex transfer-curing-implanting process. Owing to the localized deformation of PU at interfaces with AgNWs, embedding of the nanowires was rapidly carried out without substantial substrate damage. The resulting electrode retained a low sheet resistance (high electrical conductivity) of <10 Omega/sq even under 100% strain, or after 1,000 continuous stretching-relaxation cycles, with a peak strain of 60%. The fabricated electrode has found immediate application as a sensor for motion detection. Furthermore, based on our electrode, a light emitting diode (LED) driven by integrated stretchable AgNW conductors has been fabricated. In conclusion, our present fabrication approach is fast, simple, scalable, and cost-efficient, making it a good candidate for a future roll-to-roll process

Intrinsically stretchable and transparent thin-film transistors based on printable silver nanowires, carbon nanotubes and an elastomeric dielectric.

Thin-film field-effect transistor is a fundamental component behind various mordern electronics. The development of stretchable electronics poses fundamental challenges in developing new electronic materials for stretchable thin-film transistors that are mechanically compliant and solution processable. Here we report the fabrication of transparent thin-film transistors that behave like an elastomer film. The entire fabrication is carried out by solution-based techniques, and the resulting devices exhibit a mobility of ∼30 cm(2) V(-1) s(-1), on/off ratio of 10(3)-10(4), switching current &gt;100 μA, transconductance &gt;50 μS and relative low operating voltages. The devices can be stretched by up to 50% strain and subjected to 500 cycles of repeated stretching to 20% strain without significant loss in electrical property. The thin-film transistors are also used to drive organic light-emitting diodes. The approach and results represent an important progress toward the development of stretchable active-matrix displays