Highly reproducible, hysteresis-free, flexible strain sensors by inkjet printing of carbon nanotubes
TL;DR: In this paper, the reproducibility of the sensitivity, the most critical parameter for sensing application, has been only marginally assessed for carbon nanotube networks (CNNs) based resistive strain sensors fabricated by inkjet-printing on flexible Ethylene Tetrafluoroethylethylene (EFTE) sheets.
About: This article is published in Carbon.The article was published on 2015-12-01 and is currently open access. It has received 100 citations till now.
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TL;DR: In this article, a detailed overview on both strategies for sensing performance improvement and progress to medium or large-scale fabrication is presented, and a broad range of matrices/substrates and incorporated nanomaterials are covered and attention is paid to the current state-of-the-art of feasible but low-cost manufacturing methods.
210 citations
TL;DR: In this paper, an ultra-sensitive GO-based capacitive pressure sensor with graphene as electrodes was presented, which can detect a subtle pressure of ∼0.24Pa with a fast response time (∼100m) and a high sensitivity ( ∼ 0.8kPa−1).
186 citations
TL;DR: The fabrication of highly stretchable and sensitive multidirectional strain sensors with tunable strain gauge factors by employing a digitally controlled printer to incorporate carbon nanotube layers into polydimethylsiloxane (PDMS) substrates shows great application potential in motion-detecting systems.
Abstract: Strain sensors that are capable of monitoring complex human motions with high accuracy are highly desirable for developing wearable electronics. This paper reports the fabrication of highly stretchable and sensitive multidirectional strain sensors with tunable strain gauge factors by employing a digitally controlled printer to incorporate carbon nanotube (CNT) layers into polydimethylsiloxane (PDMS) substrates. The fabricated sensors exhibit a high stretchability (up to 45%) and sensitivity with a gauge factor of 35.75. The gauge factors could be easily modulated by tuning the number of CNT printing cycles to accommodate diverse requirements. The cyclic loading–unloading test results revealed that the composite strain sensors exhibited excellent long-term durability. Particularly, in this work, for the first time, human-motion-induced strain was measured by a motion capture system and compared with the strain data obtained from the fabricated strain sensors. The deviation of strains measured by composite ...
178 citations
TL;DR: Some of the challenges in current and emerging applications of CNTs in fields such as energy storage, transistors, tissue engineering, drug delivery, electronic cryptographic keys and sensors are considered.
Abstract: Carbon nanotubes (CNTs) have attracted significant interest due to their unique combination of properties including high mechanical strength, large aspect ratios, high surface area, distinct optical characteristics, high thermal and electrical conductivity, which make them suitable for a wide range of applications in areas from electronics (transistors, energy production and storage) to biotechnology (imaging, sensors, actuators and drug delivery) and other applications (displays, photonics, composites and multi-functional coatings/films). Controlled growth, assembly and integration of CNTs is essential for the practical realization of current and future nanotube applications. This review focuses on progress to date in the field of CNT assembly and integration for various applications. CNT synthesis based on arc-discharge, laser ablation and chemical vapor deposition (CVD) including details of tip-growth and base-growth models are first introduced. Advances in CNT structural control (chirality, diameter and junctions) using methods such as catalyst conditioning, cloning, seed-, and template-based growth are then explored in detail, followed by post-growth CNT purification techniques using selective surface chemistry, gel chromatography and density gradient centrifugation. Various assembly and integration techniques for multiple CNTs based on catalyst patterning, forest growth and composites are considered along with their alignment/placement onto different substrates using photolithography, transfer printing and different solution-based techniques such as inkjet printing, dielectrophoresis (DEP) and spin coating. Finally, some of the challenges in current and emerging applications of CNTs in fields such as energy storage, transistors, tissue engineering, drug delivery, electronic cryptographic keys and sensors are considered.
175 citations
TL;DR: A facile method to fabricate bidirectional strain sensors through the integration of multiwalled carbon nanotubes (MWCNT) and multimaterial additive manufacturing is reported, which has potential applications in wearable electronics, soft robotics, and prosthetics.
Abstract: Fabricating complex sensor platforms is still a challenge because conventional sensors are discrete, directional, and often not integrated within the system at the material level. Here, we report a facile method to fabricate bidirectional strain sensors through the integration of multiwalled carbon nanotubes (MWCNT) and multimaterial additive manufacturing. Thermoplastic polyurethane (TPU)/MWCNT filaments were first made using a two-step extrusion process. TPU as the platform and TPU/MWCNT as the conducting traces were then 3D printed in tandem using multimaterial fused filament fabrication to generate uniaxial and biaxial sensors with several conductive pattern designs. The sensors were subjected to a series of cyclic strain loads. The results revealed excellent piezoresistive responses with cyclic repeatability in both the axial and transverse directions and in response to strains as high as 50%. It was shown that the directional sensitivity could be tailored by the type of pattern design. A wearable glove, with built-in sensors, capable of measuring finger flexure was also successfully demonstrated where the sensors are an integral part of the system. These sensors have potential applications in wearable electronics, soft robotics, and prosthetics, where complex design, multi-directionality, embedding, and customizability are demanded.
107 citations
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TL;DR: Many potential applications have been proposed for carbon nanotubes, including conductive and high-strength composites; energy storage and energy conversion devices; sensors; field emission displays and radiation sources; hydrogen storage media; and nanometer-sized semiconductor devices, probes, and interconnects.
Abstract: Many potential applications have been proposed for carbon nanotubes, including conductive and high-strength composites; energy storage and energy conversion devices; sensors; field emission displays and radiation sources; hydrogen storage media; and nanometer-sized semiconductor devices, probes, and interconnects. Some of these applications are now realized in products. Others are demonstrated in early to advanced devices, and one, hydrogen storage, is clouded by controversy. Nanotube cost, polydispersity in nanotube type, and limitations in processing and assembly methods are important barriers for some applications of single-walled nanotubes.
9,693 citations
TL;DR: The nanotubes sensors exhibit a fast response and a substantially higher sensitivity than that of existing solid-state sensors at room temperature and the mechanisms of molecular sensing with nanotube molecular wires are investigated.
Abstract: Chemical sensors based on individual single-walled carbon nanotubes (SWNTs) are demonstrated. Upon exposure to gaseous molecules such as NO 2 or NH 3 , the electrical resistance of a semiconducting SWNT is found to dramatically increase or decrease. This serves as the basis for nanotube molecular sensors. The nanotube sensors exhibit a fast response and a substantially higher sensitivity than that of existing solid-state sensors at room temperature. Sensor reversibility is achieved by slow recovery under ambient conditions or by heating to high temperatures. The interactions between molecular species and SWNTs and the mechanisms of molecular sensing with nanotube molecular wires are investigated.
5,908 citations
"Highly reproducible, hysteresis-fre..." refers background in this paper
...Ohmic or transistor devices using CNTs deposited or grown on rigid substrates have demonstrated exceptional sensitivity to their environment, leading to various examples of analytical (humidity, pH, gas, chemical or biological species) [3], mechanical (strain, pressure) [4] or radiation (thermal or infrared, UV) [5] sensors....
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TL;DR: The tensile strengths of individual multiwalled carbon nanotubes (MWCNTs) were measured with a "nanostressing stage" located within a scanning electron microscope and a variety of structures were revealed, such as a nanotube ribbon, a wave pattern, and partial radial collapse.
Abstract: The tensile strengths of individual multiwalled carbon nanotubes (MWCNTs) were measured with a “nanostressing stage” located within a scanning electron microscope. The tensile-loading experiment was prepared and observed entirely within the microscope and was recorded on video. The MWCNTs broke in the outermost layer (“sword-in-sheath” failure), and the tensile strength of this layer ranged from 11 to 63 gigapascals for the set of 19 MWCNTs that were loaded. Analysis of the stress-strain curves for individual MWCNTs indicated that the Young's modulus E of the outermost layer varied from 270 to 950 gigapascals. Transmission electron microscopic examination of the broken nanotube fragments revealed a variety of structures, such as a nanotube ribbon, a wave pattern, and partial radial collapse.
5,011 citations
"Highly reproducible, hysteresis-fre..." refers background in this paper
...With their mechanical robustness (high Young’s modulus, low bending rigidity, low buckling properties, high tensile strength [2] [12]) flexible CNT sensors are expected to provide longlasting, reliable devices compatible with industrial requirements....
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TL;DR: Transparent, conducting spray-deposited films of single-walled carbon nanotubes are reported that can be rendered stretchable by applying strain along each axis, and then releasing this strain.
Abstract: Transparent films of carbon nanotubes can accommodate strains of up to 150% and demonstrate conductivities as high as 2,200 S cm−1 in the stretched state.
2,847 citations
"Highly reproducible, hysteresis-fre..." refers methods or result in this paper
...CNNs strain sensitivity [15] [18], the resistance longitudinal strains of up to 2500 με (Figure 1 substrate is linear (see SI7 for details on the mechanical up to 2500 με (1 με strain corresponds to an extension L), the resistance increases quadratically with strain (Figure 5a), in accordance with...
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...Their fabrication methods include filtration and extraction of buckypaper [14], spray coating [15], layer-by-layer assembly [10] as well as contact (roll-to-roll [16] or transfer-based [17]) and non-contact (aerosol [18] or inkjet [19]) printing techniques....
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TL;DR: A class of wearable and stretchable devices fabricated from thin films of aligned single-walled carbon nanotubes capable of measuring strains up to 280% with high durability, fast response and low creep is reported.
Abstract: Thin films of single-wall carbon nanotube have been used to create stretchable devices that can be incorporated into clothes and used to detect human motions.
2,790 citations
"Highly reproducible, hysteresis-fre..." refers background in this paper
...Much higher GF values can be achieved in devices with oriented CNT [8] or closer to the CNN’s percolation threshold, including buckypaperbased devices (for instance [42])....
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...Following the quick rise of CNT-based flexible electronics [6], a wide range of flexible CNT sensors was proposed [7], with the goal of providing the next generation of wearable devices [8] for human welfare monitoring or wireless sensor networks [9] for infrastructure [10] or environmental...
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