Electrical and piezoresistive properties of multi-walled carbon nanotube/polymer composite films aligned by an electric field
TL;DR: In this paper, the electrical conductivity and piezoresistive response of electric-field-aligned and randomly oriented 0.1-0.75% MWCNT/polysulfone films are evaluated.
About: This article is published in Carbon.The article was published on 2011-08-01. It has received 285 citations till now. The article focuses on the topics: Piezoresistive effect & Carbon nanotube.
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TL;DR: In this article, the authors present recent advancements in the development of flexible and stretchable strain sensors, including skin-mountable and wearable strain sensors for personalized health-monitoring, human motion detection, human-machine interfaces, soft robotics, and so forth.
Abstract: There is a growing demand for flexible and soft electronic devices. In particular, stretchable, skin-mountable, and wearable strain sensors are needed for several potential applications including personalized health-monitoring, human motion detection, human-machine interfaces, soft robotics, and so forth. This Feature Article presents recent advancements in the development of flexible and stretchable strain sensors. The article shows that highly stretchable strain sensors are successfully being developed by new mechanisms such as disconnection between overlapped nanomaterials, crack propagation in thin films, and tunneling effect, different from traditional strain sensing mechanisms. Strain sensing performances of recently reported strain sensors are comprehensively studied and discussed, showing that appropriate choice of composite structures as well as suitable interaction between functional nanomaterials and polymers are essential for the high performance strain sensing. Next, simulation results of piezoresistivity of stretchable strain sensors by computational models are reported. Finally, potential applications of flexible strain sensors are described. This survey reveals that flexible, skin-mountable, and wearable strain sensors have potential in diverse applications while several grand challenges have to be still overcome.
2,154 citations
TL;DR: By considering both the connectivity and mobility of the nanosheets, a quantitative model is developed that completely describes the electromechanical properties of graphene, allowing the manufacture of strain sensors that can detect respiration and the footsteps of spiders.
Abstract: Despite its widespread use in nanocomposites, the effect of embedding graphene in highly viscoelastic polymer matrices is not well understood. We added graphene to a lightly cross-linked polysilicone, often encountered as Silly Putty, changing its electromechanical properties substantially. The resulting nanocomposites display unusual electromechanical behavior, such as postdeformation temporal relaxation of electrical resistance and nonmonotonic changes in resistivity with strain. These phenomena are associated with the mobility of the nanosheets in the low-viscosity polymer matrix. By considering both the connectivity and mobility of the nanosheets, we developed a quantitative model that completely describes the electromechanical properties. These nanocomposites are sensitive electromechanical sensors with gauge factors >500 that can measure pulse, blood pressure, and even the impact associated with the footsteps of a small spider.
631 citations
TL;DR: A review of recent developments in the rapidly changing and advancing field of smart fabric sensor and electronic textile technologies can be found in this article, which summarizes the basic principles and approaches employed when building fabric sensors as well as the most commonly used materials and techniques used in electronic textiles.
Abstract: This paper provides a review of recent developments in the rapidly changing and advancing field of smart fabric sensor and electronic textile technologies. It summarizes the basic principles and approaches employed when building fabric sensors as well as the most commonly used materials and techniques used in electronic textiles. This paper shows that sensing functionality can be created by intrinsic and extrinsic modifications to textile substrates depending on the level of integration into the fabric platform. The current work demonstrates that fabric sensors can be tailored to measure force, pressure, chemicals, humidity and temperature variations. Materials, connectors, fabric circuits, interconnects, encapsulation and fabrication methods associated with fabric technologies prove to be customizable and versatile but less robust than their conventional electronics counterparts. The findings of this survey suggest that a complete smart fabric system is possible through the integration of the different types of textile based functional elements. This work intends to be a starting point for standardization of smart fabric sensing techniques and e-textile fabrication methods.
618 citations
TL;DR: This article reviews the recent significant developments in the field of highly sensitive strain sensors made from CNT/polymer nanocomposites and focuses on the following two topics: electrical conductivity and piezoresistivity of CNT/.
Abstract: In recent years, nanocomposites based on various nano-scale carbon fillers, such as carbon nanotubes (CNTs), are increasingly being thought of as a realistic alternative to conventional smart materials, largely due to their superior electrical properties. Great interest has been generated in building highly sensitive strain sensors with these new nanocomposites. This article reviews the recent significant developments in the field of highly sensitive strain sensors made from CNT/polymer nanocomposites. We focus on the following two topics: electrical conductivity and piezoresistivity of CNT/polymer nanocomposites, and the relationship between them by considering the internal conductive network formed by CNTs, tunneling effect, aspect ratio and piezoresistivity of CNTs themselves, etc. Many recent experimental, theoretical and numerical studies in this field are described in detail to uncover the working mechanisms of this new type of strain sensors and to demonstrate some possible key factors for improving the sensor sensitivity.
537 citations
Cites background or methods or result from "Electrical and piezoresistive prope..."
...nano-scale carbon filler particles are SWNTs [12,13,15,20], MWNTs [15,17-19,21-24,27,30-32], carbon nanofibers [24,28,34], e....
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..., SWNT or multi-walled carbon nanotube (MWNT) or carbon nanofibers were widely used [16-34]....
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...For insulating polymer matrices, there are traditional epoxy resin [21-23,27,30], flexible epoxy [28,34], PMMA [15,19], PC [17], PEO [18], PE [20], PU [24], PP [26], PSF [31,32], etc. Basically, the influence of polymer type on the piezoresistivity may be comparatively small....
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...For insulating polymer matrices, there are traditional epoxy resin [21-23,27,30], flexible epoxy [28,34], PMMA [15,19], PC [17], PEO [18], PE [20], PU [24], PP [26], PSF [31,32], etc....
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...An interesting phenomenon in [31] is that after adjusting the alignment of MWNTs using applied AC voltages, the linear piezoresistivity has been obtained....
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TL;DR: In this article, the embedding of carbon nanotubes (CNTs) and graphene nanoplatelets (GNPs) into pristine epoxy endows optimum dispersion of CNTs and GNPs as well as better interfacial adhesion between the carbon fillers and matrix, which results in a significant improvement in load transfer effectiveness.
382 citations
References
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TL;DR: A review of recent advances in carbon nanotubes and their composites can be found in this article, where the authors examine the research work reported in the literature on the structure and processing of carbon Nanotubes.
4,709 citations
"Electrical and piezoresistive prope..." refers background in this paper
...cal properties of CNTs [1,2] and the versatility of polymers render multifunctional properties to CNT/polymer composites having both sensing and actuating capabilities [3–6]....
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...[1] Thostenson ET, Ren ZF, Chou TW....
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TL;DR: Large panels of aligned carbon nanotubes can be made under conditions that are suitable for device fabrication under plasma-enhanced hot filament chemical vapor deposition.
Abstract: Free-standing aligned carbon nanotubes have previously been grown above 700°C on mesoporous silica embedded with iron nanoparticles. Here, carbon nanotubes aligned over areas up to several square centimeters were grown on nickel-coated glass below 666°C by plasma-enhanced hot filament chemical vapor deposition. Acetylene gas was used as the carbon source and ammonia gas was used as a catalyst and dilution gas. Nanotubes with controllable diameters from 20 to 400 nanometers and lengths from 0.1 to 50 micrometers were obtained. Using this method, large panels of aligned carbon nanotubes can be made under conditions that are suitable for device fabrication.
2,530 citations
"Electrical and piezoresistive prope..." refers background in this paper
...[16] Ren ZF, Huang ZP, Xu JU, Wang JH....
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...Alignment of CNTs in CNT/polymer composites induces anisotropy in the composite, improving its physical properties in the alignment direction [16–19]....
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TL;DR: Predictions based on measurements suggest that actuators using optimized nanotube sheets may eventually provide substantially higher work densities per cycle than any previously known technology.
Abstract: Electromechanical actuators based on sheets of single-walled carbon nanotubes were shown to generate higher stresses than natural muscle and higher strains than high-modulus ferroelectrics. Like natural muscles, the macroscopic actuators are assemblies of billions of individual nanoscale actuators. The actuation mechanism (quantum chemical-based expansion due to electrochemical double-layer charging) does not require ion intercalation, which limits the life and rate of faradaic conducting polymer actuators. Unlike conventional ferroelectric actuators, low operating voltages of a few volts generate large actuator strains. Predictions based on measurements suggest that actuators using optimized nanotube sheets may eventually provide substantially higher work densities per cycle than any previously known technology.
2,334 citations
"Electrical and piezoresistive prope..." refers background in this paper
...[9] are among the pioneering groups who first reported electromechanical actuation of CNTs....
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TL;DR: Experimental and theoretical elucidation of the electromechanical characteristics of individual single-walled carbonnanotubes (SWNTs) under local-probe manipulation are reported and it is revealed that the conductance of an SWNT sample can be reduced by two orders of magnitude when deformed by an AFM tip.
Abstract: The effects of mechanical deformation on the electrical properties of carbonnanotubes are of interest given the practical potential of nanotubes in electromechanicaldevices, and they have been studied using both theoretical1,2,3,4and experimental5,6 approaches. One recent experiment6 used the tip of an atomic force microscope (AFM) to manipulate multi-wallednanotubes, revealing that changes in the sample resistance were small unlessthe nanotubes fractured or the metal–tube contacts were perturbed. Butit remains unclear how mechanical deformation affects the intrinsic electricalproperties of nanotubes. Here we report an experimental and theoretical elucidationof the electromechanical characteristics of individual single-walled carbonnanotubes (SWNTs) under local-probe manipulation. We use AFM tips to deflectsuspended SWNTs reversibly, without changing the contact resistance; insitu electrical measurements reveal that the conductance of an SWNT samplecan be reduced by two orders of magnitude when deformed by an AFM tip. Ourtight-binding simulations indicate that this effect is owing to the formationof local sp3 bonds caused by the mechanical pushingaction of the tip.
1,172 citations
"Electrical and piezoresistive prope..." refers methods in this paper
...[10]; large, reversible changes in electrical conductivity were observed by this group when they locally deformed a metallic SWCNT using an atomic force microscope....
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TL;DR: In this article, the thermal conductivity of nanotubes' dependence on structure, defects and vacancies was studied using the empirical bond order dependent force field, and it was shown that the carbon nanotube bundles have very high thermal conductivities comparable to diamond crystal and in-plane graphite sheet.
Abstract: As the sizes of electronic and mechanical devices are decreased to the micron and nanometre level, it becomes particularly important to predict the thermal transport properties of the components. Using molecular level theories, such predictions are particularly important for modelling nano-electronic devices where scaling laws may change substantially but it is most difficult to accurately measure the properties. Hence, using the empirical bond order dependent force field, we have studied here the thermal conductivity of nanotubes' dependence on structure, defects and vacancies. The anisotropic character of the thermal conductivity of the graphite crystal is naturally reflected in the carbon nanotubes. We found that the carbon nanotubes have very high thermal conductivity comparable to diamond crystal and in-plane graphite sheet. In addition, nanotube bundles show very similar properties as graphite crystal in which dramatic difference in thermal conductivities along different crystal axis.
1,073 citations
"Electrical and piezoresistive prope..." refers background in this paper
...[2] Che JW, Cagin T, Goddard WA....
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...cal properties of CNTs [1,2] and the versatility of polymers render multifunctional properties to CNT/polymer composites having both sensing and actuating capabilities [3–6]....
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