Carbon nanotube four-terminal devices for pressure sensing applications

Carbon nanotubes (CNTs) are of high interest for sensing applications,owing to their superior mechanical strength, high Young’s modulus and low density. In this work, we report on a facile approach for the fabrication of carbon nanotube devices using a four terminal configuration. Oriented carbon nanotube films were pulled out from a CNT forest wafer and then twisted into a yarn. Both the CNT film and yarn were arranged on elastomer membranes/diaphragms which were arranged on a laser cut acrylic frame to form pressure sensors. The sensors were calibrated using a precisely controlled pressure system, showing a large change of the output voltage of approximately 50 mV at a constant supply current of 100 μA and under a low applied pressure of 15 mbar. The results indicate the high potential of using CNT films and yarns for pressure sensing applications

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

Exfoliated Graphite Nanoplatelet-Carbon Nanotube Hybrid Composites for Compression Sensing

In this study, we investigated the gauge factor and compressive modulus of hybrid nanocomposites of exfoliated graphite nanoplatelets (xGnP) and multiwalled carbon nanotubes (MWCNTs) in a polydimethylsiloxane matrix under compressive strain. Mechanical and electrical tests were conducted to investigate the effects of nanofiller wt %, the xGnP size, and xGnP:MWCNT ratio on the compressive modulus and sensitivity of the sensors. It was found that nanofiller wt %, the xGnP size, and xGnP:MWCNT ratio significantly affect the electromechanical properties of the sensor. The compressive modulus increased with an increase in the nanofiller wt % and a decrease in the xGnP size and xGnP:MWCNT ratio. However, the gauge factor decreases with a decrease in the nanofiller wt % and xGnP size and an increase in the xGnP:MWCNT ratio. Therefore, by investigating the piezoresistive effects of various factors for sensing performance, such as wt %, xGnP size, and xGnP:MWCNT ratio, the concept of one- and two-dimensional hybrid fillers provides an effective way to tune both mechanical properties and sensitivity of nanocomposites by tailoring the network structure of fillers

Characterization of vertically aligned carbon nanotube forests grown on stainless steel surfaces

Vertically aligned carbon nanotube (CNT) forests are a particularly interesting class of nanomaterials, because they combine multifunctional properties, such as high energy absorption, compressive strength, recoverability and super-hydrophobicity with light weight. These characteristics make them suitable for application as coating, protective layers and antifouling substrates for metallic pipelines and blades. Direct growth of CNT forests on metals offers the possibility to transfer the tunable CNT functionalities directly onto the desired substrates. Here, we focus on characterizing the structure and mechanical properties, as well as wettability and adhesion of CNT forests grown on different types of stainless steel. We investigate the correlations between composition and morphology of the steel substrates with the micro-structure of the CNTs, and reveal how the latter ultimately controls the mechanical and wetting properties of the CNT forest. Additionally, we study the influence of substrate morphology on the adhesion of CNTs to their substrate. We highlight that the same structure-property relationships govern the mechanical performance of CNT forests grown on steels and on Si

A Review of Smart Materials in Tactile Actuators for Information Delivery

As the largest organ in the human body, the skin provides the important sensory channel for humans to receive external stimulations based on touch. By the information perceived through touch, people can feel and guess the properties of objects, like weight, temperature, textures, and motion, etc. In fact, those properties are nerve stimuli to our brain received by different kinds of receptors in the skin. Mechanical, electrical, and thermal stimuli can stimulate these receptors and cause different information to be conveyed through the nerves. Technologies for actuators to provide mechanical, electrical or thermal stimuli have been developed. These include static or vibrational actuation, electrostatic stimulation, focused ultrasound, and more. Smart materials, such as piezoelectric materials, carbon nanotubes, and shape memory alloys, play important roles in providing actuation for tactile sensation. This paper aims to review the background biological knowledge of human tactile sensing, to give an understanding of how we sense and interact with the world through the sense of touch, as well as the conventional and state-of-the-art technologies of tactile actuators for tactile feedback delivery

Computational design of chemical nanosensors: Transition metal doped single-walled carbon nanotubes

We present a general approach to the computational design of nanostructured chemical sensors. The scheme is based on identification and calculation of microscopic descriptors (design parameters) which are used as input to a thermodynamic model to obtain the relevant macroscopic properties. In particular, we consider the functionalization of a (6,6) metallic armchair single-walled carbon nanotube (SWNT) by nine different 3d transition metal (TM) atoms occupying three types of vacancies. For six gas molecules (N_{2}, O_{2}, H_{2}O, CO, NH_{3}, H_{2}S) we calculate the binding energy and change in conductance due to adsorption on each of the 27 TM sites. For a given type of TM functionalization, this allows us to obtain the equilibrium coverage and change in conductance as a function of the partial pressure of the "target" molecule in a background of atmospheric air. Specifically, we show how Ni and Cu doped metallic (6,6) SWNTs may work as effective multifunctional sensors for both CO and NH_{3}. In this way, the scheme presented allows one to obtain macroscopic device characteristics and performance data for nanoscale (in this case SWNT) based devices.Comment: Chapter 7 in "Chemical Sensors: Simulation and Modeling", Ghenadii Korotcenkov (ed.), 47 pages, 22 figures, 10 table

Carbon nanotube-based sensor and method for detection of crack growth in a structure

A sensor has a plurality of carbon nanotube (CNT)-based conductors operatively positioned on a substrate. The conductors are arranged side-by-side, such as in a substantially parallel relationship to one another. At least one pair of spaced-apart electrodes is coupled to opposing ends of the conductors. A portion of each of the conductors spanning between each pair of electrodes comprises a plurality of carbon nanotubes arranged end-to-end and substantially aligned along an axis. Because a direct correlation exists between the resistance of a carbon nanotube and its strain, changes experienced by the portion of the structure to which the sensor is coupled induce a corresponding change in the electrical properties of the conductors, thereby enabling detection of crack growth in the structure