Aligned carbon nanotube based sensors for strain sensing applications

Santos, A.; Amorim, Luís Manuel Machado; Nunes, João Arriscado; Rocha, Licinio; Silva, A.F.; Viana, J. C.

doi:10.1016/j.sna.2019.02.026

Cited by 23 publications

(28 citation statements)

References 20 publications

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“…Also, a silver conductive epoxy adhesive (8330S from MG Chemicals) was used as electrodes between the samples and the copper wires and placed at the corners of the CNT patch. A detailed description of this procedure can be found can elsewhere [3].…”

Section: Methodsmentioning

confidence: 99%

“…From aerospace to microelectronic applications, the growing demand for multifunctional materials with a set of outstanding properties put carbon nanotubes (CNTs) on the map of the most promising ones [1,2]. While CNTs mechanical performance and piezoresistive response make them suitable for sensing applications, the electric anisotropy of aligned CNTs can be used to infer strain directions [3]. This nanomaterial can be incorporated into polymer-based sensors in several ways:As conductive fillers in polymer nanocomposites [4,5], through mechanical mixing and deposition methods, such as coating, dip casting, and filtration, among others;As Buckypaper films (BP), produced by dispersion and deposition methods, such as vacuum filtration (the most common method), drop casting, or hot-press compression, among others [6,7];As vertically aligned CNT forests (VA-CNTs), synthesized by chemical vapor deposition (CVD), incorporated into polymeric matrices and substrates [8,9]; andAs vertically aligned CNT forests (VA-CNTs), synthesized by laser-oriented deposition (LOD) method directly into the matrices, allowing the incorporation of CNTs due to the covalent bounds formed during the process [10].…”

Section: Introductionmentioning

confidence: 99%

“…Alternatively, VA-CNTs, widely produced by CVD, can be knocked down and form a kind of aligned CNT Buckypaper. Recently, this technique was used to produce microheaters [23], to improve inter-laminar facture toughness on laminated composites [24], and to develop CNT/polymer strain sensors [3]. In this latter case, a patch of knocked-down VA-CNTs was laid down over a polymeric film substrate, and four conductive electrodes of Ag ink were placed for electrical connections, allowing the measurement of electrical resistance over orthogonal axes.…”

Section: Introductionmentioning

confidence: 99%

“…In this work, two types of CNT/polymer strain sensors are compared, based on:Buckypapers, in which CNTs are randomly dispersed with two different solvents and show an isotropic electrical behavior, and;Knocked-down VA-CNTs, which are highly aligned in one direction and show anisotropic electrical properties (and were developed in our previous work [3]).…”

Section: Introductionmentioning

confidence: 99%

“…Knocked-down VA-CNTs, which are highly aligned in one direction and show anisotropic electrical properties (and were developed in our previous work [3]).…”

Section: Introductionmentioning

confidence: 99%

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A Comparative Study between Knocked-Down Aligned Carbon Nanotubes and Buckypaper-Based Strain Sensors

et al. 2019

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Carbon nanotubes (CNTs) are one of the most promising materials in sensing applications due to their electrical and mechanical properties. This paper presents a comparative study between CNT Buckypaper (BP) and aligned CNT-based strain sensors. The Buckypapers were produced by vacuum filtration of commercial CNTs dispersed in two different solvents, N,N-Dimethylformamide (DMF) and ethanol, forming freestanding sheets, which were cut in 10 × 10 mm squares and transferred to polyimide (PI) films. The morphology of the BP was characterized by scanning electron microscopy (SEM). The initial electrical resistivity of the samples was measured, and then relative electrical resistance versus strain measurements were obtained. The results were compared with the knocked-down vertically aligned CNT/PI based sensors previously reported. Although both types of sensors were sensitive to strain, the aligned CNT/PI samples had better mechanical performance and the advantage of inferring strain direction due to their electrical resistivity anisotropic behavior.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…Knocked-down VA-CNTs, which are highly aligned in one direction and show anisotropic electrical properties (and were developed in our previous work [3]).…”

Section: Introductionmentioning

confidence: 99%

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A Comparative Study between Knocked-Down Aligned Carbon Nanotubes and Buckypaper-Based Strain Sensors

et al. 2019

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Recent Trends of Bioanalytical Sensors with Smart Health Monitoring Systems: From Materials to Applications

Vo,

Hoang,

et al. 2024

Adv Healthcare Materials

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Smart biosensors attract significant interest due to real‐time monitoring of user health status, in which bioanalytical electronic devices designed to detect and track various activities and biomarkers in the human body have potential applications in physical sign monitoring and health care. Bioelectronics can also be well integrated by output signals with wireless communication modules for transferring data to portable devices used as smart biosensors in performing real‐time diagnosis and analysis. In this review, the scientific keys of bio‐sensing devices and the current trends in the field of smart biosensors, i.e., functional materials, technological approaches, readout circuits, sensing mechanisms, main roles, potential applications in health monitoring, and challenges in future works, will be summarized and highlighted. Recent advances in the design and manufacturing of bioanalytical sensors with smarter capabilities and enhanced reliability indicate a forthcoming expansion of these smart electronic devices from lab to clinical analysis. Therefore, a general description of functional materials and technological approaches used in bioelectronics will be presented after the sections of scientific keys to bioanalytical sensors. A careful introduction to the established systems of smart monitoring and prediction analysis using bioelectronics, regarding the integration of machine‐learning‐based basic algorithms, will be discussed. Afterward, potential applications and challenges in development using these smart bioelectronics in biological, clinical, and medical diagnostics will also be analyzed. Finally, the review will conclude with outlooks of smart bio‐sensing devices assisted by machine learning algorithms, wireless communications, or smartphone‐based systems on current trends and challenges for future works in wearable health monitoring.This article is protected by copyright. All rights reserved

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1.1‐Millimeter Tall Vertically Aligned‐Carbon Nanotubes Grown by Cold Wall CVD Using a Novel Multiple‐Purge Method

Coelho

Machado

2022

Adv Materials Inter

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These processes still have limitation in achieving high yield and quality, and any commercial use of CNTs is limited due to these challenges encountered in large scale synthesis. [17] According to Shi et al. (2017), [18] "The poor reproducibility in CNT synthesis via CVD has been attributed to fluctuations in ambient and reactor-sorbed water vapor, as well as to carbonaceous deposits inside reactors leading to growth hysteresis." The presence of water or oxygen influences the growth gases and contributes to the formation or removal of carbon coated on the catalyst nanoparticles and avoiding this block deposition. The formation of carbon block coated on the catalyst nanoparticles prevents the CNT forests to grow taller, terminating the growth process. Thus, to obtain taller CNT forests, the lifetime of the catalyst should be prolonged. [17] The abrupt saturation point is observed for CNT growth rate controlled by laser with Meshot and Hart ( 2008). [19] The carbon atoms that reach the catalyst nanoparticles contribute to the CNT growth, but they also coat in form of amorphous carbon on the nanoparticle. Xiang et al. ( 2008) [20] refers to the growth limits of CNT carpets, explaining the diffusion mechanism of precursors for several different methods. Xiang et al. ( 2007) [21] refers the catalyst encapsulation occurs and it can be controlled during the growth changing the saturation point, creating a continuous growth mechanism. This deposition can be controlled by continuously supplying an etchant material that etches out the amorphous carbon coated on the catalyst nanoparticles. [17] The etchant materials generally used are CO 2 , H 2 O, and O 2 , however, excess levels of oxygencontaining compounds can result in etching of the CNTs themselves. [18] Sugime et al. ( 2021) [22] using the hot wire filament grew CNT around 14 cm but in this case the industrial growth is far in terms of reproducibility in quantity.Recently, Machado Jr. and Coelho (2021) [23] reported a novel method to obtain 140 µm tall VA-CNT forests, using a coldwall technique based on a two-phase deposition step. The first phase consists of the flow of NH 3 for a short period of time together with the C 2 H 2 flow to ensure catalyst activation. In the second phase, NH 3 flow is replaced by H 2 flow during the remaining growth time, permitting to obtain tall VA-CNT forests. In this work the saturation point was reached before the 40 min on deposition step in order to get 140 µm. Furthermore, the annealing temperature should be lower than the growth temperature to obtain taller forests. [24] Moreover, adding a third phase of H 2 during the deposition step at a temperature 50 °C above the previous phase, including a purge between each phase, allowed to achieve forests as high and uniform as This paper reports a multi-phase deposition for the growth of carbon nanotubes, intercalating phases of effective growth with purges of the reactor, based on the method recently proposed by the author to grow tall vertically aligned carbon nanotubes (VA-CNT) in a c...

show abstract

Aligned carbon nanotube based sensors for strain sensing applications

Cited by 23 publications

References 20 publications

A Comparative Study between Knocked-Down Aligned Carbon Nanotubes and Buckypaper-Based Strain Sensors

A Comparative Study between Knocked-Down Aligned Carbon Nanotubes and Buckypaper-Based Strain Sensors

Recent Trends of Bioanalytical Sensors with Smart Health Monitoring Systems: From Materials to Applications

1.1‐Millimeter Tall Vertically Aligned‐Carbon Nanotubes Grown by Cold Wall CVD Using a Novel Multiple‐Purge Method

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