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Nankali, M., NM Nouri, N. Geran Malek i MA Sanjari Shahrezaei. "Electrical properties of stretchable and skin–mountable PDMS/MWCNT hybrid composite films for flexible strain sensors". Journal of Composite Materials 53, nr 21 (29.06.2019): 3047–60. http://dx.doi.org/10.1177/0021998319853034.
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Flexible strain sensors based on carbon nanofillers have great potential in the application of skin-adhesive sensors, wearable sensors, and tactile sensors, due to their superior electrical properties. Herein, the electrical properties of highly sensitive PDMS/MWCNT strain sensors made by vacuum filtration method were investigated. In order to obtain the electrical percolation curve of the flexible conductive films, first different samples were made with the same surface area but with different wt. % of CNTs. Then, depending on CNT content, the obtained conductive films exhibited initial electrical resistance in the range of 12.5 KΩ to 22.8 MΩ. The piezoresistive films with the CNT concentration of 1.4 to 2.9 [Formula: see text] had shown superior resistance drop, so this interval was determined as the percolation threshold region. According to the SEM images, the nanocomposite layer thickness of the flexible strain sensors in this region was 790 nm to 1210 nm. Afterward, the percolation curve was obtained using curve fitting to the experimental data and the exact value of the percolation threshold was defined as [Formula: see text]. Finally, in order to determine the minimum gauge factor ([Formula: see text]) of the sensors in percolation region, a flexible strain sensor in the upper limit of this region was selected and the piezoresistive properties of the selected sample were investigated.
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Kumar, Ankush. "Electrical Percolation in Metal Wire Network-Based Strain Sensors". IEEE Sensors Journal 19, nr 22 (15.11.2019): 10373–78. http://dx.doi.org/10.1109/jsen.2019.2933239.
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Du, Zhengyang, Ji’an Chen, Chang Liu, Chen Jin i Min Han. "Controllable Fabrication of Percolative Metal Nanoparticle Arrays Applied for Quantum Conductance-Based Strain Sensors". Materials 13, nr 21 (29.10.2020): 4838. http://dx.doi.org/10.3390/ma13214838.
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We use gas phase deposition of well-defined nanoparticles (NPs) to fabricate closely-spaced Pd NP arrays on flexible membranes prepatterned with interdigital electrodes (IDEs). The evolution of the morphology and electron conductance of the NP arrays during deposition is analyzed. The growth of two-dimensional percolation clusters of interconnected NPs, which correlate with the percolation pathway for electron conduction in the NP deposits, is demonstrated. The percolative nature of the NP arrays permits us to finely control the percolation geometries and conductance of the NP film by controlling the NP deposition time so as to realize a precise and reproducible fabrication of sensing materials. Electron transport measurements reveal that the electrical conductance of the NP films is dominated by electron tunneling or hopping across the NP percolating networks. Based on the percolative and quantum tunneling nature, the closely-spaced Pd NP films on PET membranes are used as flexible strain sensors. The sensor demonstrates an excellent response ability to distinguish tiny deformations down to 5×10−4 strain and a high sensitivity with a large gauge factor of 200 up to 4% applied strain.
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Bobkov, Anton, Victor Luchinin, Vyacheslav Moshnikov, Svetlana Nalimova i Yulia Spivak. "Impedance Spectroscopy of Hierarchical Porous Nanomaterials Based on por-Si, por-Si Incorporated by Ni and Metal Oxides for Gas Sensors". Sensors 22, nr 4 (16.02.2022): 1530. http://dx.doi.org/10.3390/s22041530.
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Approaches are being developed to create composite materials with a fractal-percolation structure based on intercalated porous matrices to increase the sensitivity of adsorption gas sensors. Porous silicon, nickel-containing porous silicon, and zinc oxide have been synthesized as materials for such structures. Using the impedance spectroscopy method, it has been shown that the obtained materials demonstrate high sensitivity to organic solvent vapors and can be used in gas sensors. A model is proposed that explains the high sensitivity and inductive nature of the impedance at low frequencies, considering the structural features and fractal-percolation properties of the obtained oxide materials.
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Sapra, Gaurav, Renu Vig i Manu Sharma. "Simulation and Analysis of Strain Sensitivity of CNT-Based Strain Sensors". International Journal of Nanoscience 15, nr 05n06 (październik 2016): 1660005. http://dx.doi.org/10.1142/s0219581x1660005x.
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Carbon nanotubes (CNT) is turning out to be a replacement to all the existing traditional sensors due to their high gauge factor, multidirectional sensing capability, high flexibility, low mass density, high dynamic range and high sensitivity to strains at nano and macro- scales. The strain sensitivity of CNT-based strain sensors depends on number of parameters; quality and quantity of CNT used, type of polymer used, deposition and dispersion technique adopted and also on environmental conditions. Due to all these parameters, the piezoresistive behavior of CNT is diversified and it needs to be explored. This paper theoretically analyses the strain sensitivity of CNT-based strain sensors. The strain sensitivity response of CNT strain sensor is a result of change in total resistance of CNT network with respect to applied strain. The total resistance of CNT network consists of intrinsic resistance and inter-tube resistance. It has been found that the change in intrinsic resistance under strain is due to the variation of bandgap of individual, which depends on the chirality of the tube and it varies exponentially with strain. The inter-tube resistance of CNT network changes nonlinearly due to change in distance between neighboring CNTs with respect to applied strain. As the distance [Formula: see text] between CNTs increases due to applied strain, tunneling resistance [Formula: see text] increases nonlinearly in exponential manner. When the concentration of CNTs in composite is close to percolation threshold, then the change of inter-tube resistances is more dominant than intrinsic resistance. At percolation threshold, the total resistance of CNT networks changes nonlinearly and this effect of nonlinearity is due to tunneling effect. The strain sensitivity of CNT-based strain sensors also varies nonlinearly with the change in temperature. For the change of temperature from [Formula: see text]C to 50[Formula: see text]C, there is more than 100% change in strain sensitivity of CNT/polymer composite strain sensor. This change is mainly due to the infiltration of polymer into CNTs.
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Hu, Bin, Yaolu Liu, Ning Hu, Liangke Wu, Huiming Ning, Jianyu Zhang, Shaoyun Fu i in. "Conductive PVDF-HFP/CNT composites for strain sensing". Functional Materials Letters 09, nr 02 (kwiecień 2016): 1650024. http://dx.doi.org/10.1142/s1793604716500247.
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A strain sensor based on the composites of poly (vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) filled by multi-walled carbon nanotube (MWNT) was prepared using a proposed fabrication process. Three kinds of MWNT loadings, i.e., 1.0[Formula: see text]wt.%, 2.0[Formula: see text]wt.% and 3.0[Formula: see text]wt.% were employed. Due to good dispersion state of MWNT in PVDF-HFP matrix, which was characterized by scanning electron microscope (SEM), this sensor was found to be of high sensitivity and stable performance. The sensor’s piezoresistivity varied in a weak nonlinear pattern, which was probably caused by the tunneling effect among neighboring MWNTs. The gauge factor of the sensor of 1.0[Formula: see text]wt.% MWNT loading was identified to be the highest, i.e., 33. This sensor gauge factor decreased gradually with the increase of addition amount of MWNT, which was 5 for the sensor of 3.0[Formula: see text]wt.% MWNT loading. This gauge factor was still higher than that of conventional metal-foil strain sensors. The electrical conductivity of PVDF-HFP/MWNT composites was also studied. It was found that with the increase of the addition amount of MWNT, the electrical conductivity of the PVDF-HFP/MWNT composites varied in a perfect percolation pattern with a very low percolation threshold, i.e., 0.77 vol.%, further indicating the very good dispersion of MWNT in the PVDF-HFP matrix.
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Lefferts, Merel Jolijn, Ben I. Armitage, Krishnan Murugappan, Tabitha Jones i Martin R. Castell. "Chemiresistive Vapour Sensors Based on a Percolation Network of Conductive Polymers". ECS Meeting Abstracts MA2020-01, nr 28 (1.05.2020): 2097. http://dx.doi.org/10.1149/ma2020-01282097mtgabs.
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Piromjitpong, T., P. Lorwongtragool, P. Piromjitpong i Teerakiat Kerdcharoen. "The Efficiency Development of Ammonia-Odor Sensor Based on PSE-Polymer/SWNT Nanocomposite". Advanced Materials Research 506 (kwiecień 2012): 579–82. http://dx.doi.org/10.4028/www.scientific.net/amr.506.579.
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In this work, we have investigated and optimized the fabrication process of ammonia sensor based on poly (styrene-co-maleic acid) partial isobutyl/methyl mixed ester/single-wall carbon nanotubes (PSE/SWNT) nanocomposite leading to the standardized and highly efficiency of device. The proper ratio of sensing material loading was achieved by varying the SWNT concentration to reach to the best sensing properties. PSE/SWNT sensors were fabricated by spin-coating technique on the interdigitated gold electrodes by controlling the reference resistance in range of 1-10 kΩ. Two groups of the fabricated sensors (carboxylic functionalized SWNT (SWNT-COOH) and hydroxyl functionalized SWNT (SWNT-OH)) with five different percent loadings were tested with various concentrations of ammonia volatile. Electrical resistances of these sensors were measured and modeled on the percolation theory approach, in order to explain and determine the appropriate composition from their mechanisms.
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Pershad, Yash, Ashley A. Mascareno, Makoyi R. Watson, Alex L. Brimhall, Nicole Herbots, Clarizza F. Watson, Abijith Krishnan i in. "Electrolyte Detection by Ion Beam Analysis, in Continuous Glucose Sensors and in Microliters of Blood using a Homogeneous Thin Solid Film of Blood, HemaDrop™". MRS Advances 1, nr 29 (2016): 2133–39. http://dx.doi.org/10.1557/adv.2016.469.
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ABSTRACTPercolation of blood and of interstitial fluids into implantable continuous glucose sensors (CGS) for diabetics presently limits sensor lifetime between 3 and 7 days. Na+ mobile ions in body fluids damage Si-based CGS sensors electronics. The direct detection of Na percolation is investigated by Ion Beam Analysis (IBA) and Proton Induced X-ray Emission (PIXE) in previously used CGS. Based on these results, a new technology called HemaDropTM is then tested to prepare small volume (5-10 µL) of blood for IBA. A species’s detectability by IBA scales with the square of the ratio of element’s atomic number Z to that of the substrate. Because Na has a low atomic number (Z=11), Si signals from sensor substrates can prevent Na detection in Si by 2 mega electron volt (MeV) IBA.Using 4.7 MeV 23Na (α, α)23Na nuclear resonance (NR) can increase the 23Na scattering cross section and thus its detectability in Si. The NR energy, width, and resonance factor, is calibrated via two well-known alpha (α) particle signals with narrow energy spreads: a 5.486 ± 0.007 MeV 241Am α-source (ΔΕ = 0.12%) and the 3.038 ± 0.003 MeV 16O(α, α)16O NR (ΔΕ = 0.1%). Next, the NR cross section is calibrated via 100 nm NaF thin films on Si(100) by scanning the beam energy. The23Na (α, α) NR energy is found to be 4.696 ± 0.180 MeV, and the NR/RBS cross section 141 ± 7%. This is statistically significant but small compared to the 4.265 MeV 12C NR (1700%) and 3.038 MeV 16O NR (210%), and insufficient to detect small amounts of 23Na in Si. Next, a new method of sample preparation HemaDropTM, is tested for detection of elements in blood, such Fe, Ca, Na, Cl, S, K, C, N, and O, as an alternative to track fluid percolation and Na diffusion in damaged sensors. Detecting more abundant, heavier elements in blood and interstitial fluids can better track fluid percolation and Na+ ions in sensors. Both Na detection and accuracy of measured blood composition by IBA is greatly improved by using HemaDropTM sample preparation to create Homogeneous Thin Solid Films (HTSFs) of blood from 5-10 µL on most substrates. HTSF can be used in vacuo such as 10-8 –10-6 Torr).
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Alam, Md Jobair Bin, Asif Ahmed, Md Sahadat Hossain i Naima Rahman. "Estimation of percolation of water balance cover using field scale unsaturated soil parameter". MATEC Web of Conferences 337 (2021): 04005. http://dx.doi.org/10.1051/matecconf/202133704005.
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Water balance covers for landfill closure are used as a barrier which act with the natural processes to reduce percolation. The ideal performance of water balance cover is characterized by the minimal quantity of percolation. The rate of percolation of water balance cover largely depends on unsaturated soil behavior. In this study, percolation was evaluated through unsaturated soil parameters of six instrumented lysimeters. The field instrumentation included moisture sensors, tensiometers, rain gauge, dosing siphon, and pressure transducer. Soil water storage (SWS) capacity (SA) was quantified from the soil water characteristic curves (SWCC) which were developed based on laboratory experiments and field instrumentation data. Required SWS (SR) was also measured from the field monitoring results. Based on analysis, the relative storage ratio (SR/SA) was observed to be greater than unity (1) in most of the cases, indicating potential percolation. The SR/SA was also found competent to identify the lysimeter with higher quantity of percolations. The estimated percolation from the laboratory experimented and field generated SWCCs fairly resembled with the actual field measured percolation. The analyzed results also developed a framework to estimate the thickness of the cover storage layer required to manage percolation for the specific region of the study area.
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Nabeel, Mohammed, Miklós Varga, László Kuzsella, Béla Fiser, László Vanyorek i Béla Viskolcz. "The Effect of Pore Volume on the Behavior of Polyurethane-Foam-Based Pressure Sensors". Polymers 14, nr 17 (2.09.2022): 3652. http://dx.doi.org/10.3390/polym14173652.
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In this work, three different polyurethane (PU) foams were prepared by mixing commonly used isocyanate and polyol with different isocyanate indices (1.0:0.8, 1.0:1.0, 1.0:1.1). Then, the prepared polyurethane foam samples were coated by dip-coating with a fixed ratio of nitrogen-doped, bamboo-shaped carbon nanotubes (N-BCNTs) to obtain pressure sensor systems. The effect of the isocyanate index on the initial resistance, pressure sensitivity, gauge factor (GF), and repeatability of the N-BCNT/PU pressure sensor systems was studied. The pore volume was crucial in finetuning the PU-foam-based sensors ability to detect large strain. Furthermore, large pore volume provides suitable spatial pores for elastic deformation. Sensors with large pore volume can detect pressure of less than 3 kPa, which could be related to their sensitivity in the high range. Moreover, by increasing the pore volume, the electrical percolation threshold can be achieved with a minimal addition of nanofillers. On the other hand, PU with a smaller pore volume is more suitable to detect pressure above 3 kPa. The developed sensors have been successfully applied in many applications, such as motion monitoring and vibration detection.
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Serban, Bogdan-Catalin, Cornel Cobianu, Niculae Dumbravescu, Octavian Buiu, Marius Bumbac, Cristina Mihaela Nicolescu, Cosmin Cobianu, Mihai Brezeanu, Cristina Pachiu i Matei Serbanescu. "Electrical Percolation Threshold and Size Effects in Polyvinylpyrrolidone-Oxidized Single-Wall Carbon Nanohorn Nanocomposite: The Impact for Relative Humidity Resistive Sensors Design". Sensors 21, nr 4 (19.02.2021): 1435. http://dx.doi.org/10.3390/s21041435.
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This paper reports, for the first time, on the electrical percolation threshold in oxidized carbon nanohorns (CNHox)–polyvinylpyrrolidone (PVP) films. We demonstrate—starting from the design and synthesis of the layers—how these films can be used as sensing layers for resistive relative humidity sensors. The morphology and the composition of the sensing layers are investigated through Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), and RAMAN spectroscopy. For establishing the electrical percolation thresholds of CNHox in PVP, these nanocomposite thin films were deposited on interdigitated transducer (IDT) dual-comb structures. The IDTs were processed both on a rigid Si/SiO2 substrate with a spacing of 10 µm between metal digits, and a flexible substrate (polyimide) with a spacing of 100 µm. The percolation thresholds of CNHox in the PVP matrix were equal to (0.05–0.1) wt% and 3.5 wt% when performed on 10 µm-IDT and 100 µm-IDT, respectively. The latter value agreed well with the percolation threshold value of about 4 wt% predicted by the aspect ratio of CNHox. In contrast, the former value was more than an order of magnitude lower than expected. We explained the percolation threshold value of (0.05–0.1) wt% by the increased probability of forming continuous conductive paths at much lower CNHox concentrations when the gap between electrodes is below a specific limit. The change in the nanocomposite’s longitudinal Young modulus, as a function of the concentration of oxidized carbon nanohorns in the polymer matrix, is also evaluated. Based on these results, we identified a new parameter (i.e., the inter-electrode spacing) affecting the electrical percolation threshold in micro-nano electronic devices. The electrical percolation threshold’s critical role in the resistive relative-humidity sensors’ design and functioning is clearly emphasized.
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Zhang, Qingtian, Guolin Yun, Shida Jin, Zexin Chen, Shi-Yang Tang, Hongda Lu, Haiping Du i Weihua Li. "Silver Nanoflakes-Enhanced Anisotropic Hybrid Composites for Integratable Pressure Sensors". Nanomaterials 12, nr 22 (16.11.2022): 4018. http://dx.doi.org/10.3390/nano12224018.
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Flexible pressure sensors based on polymer elastomers filled with conductive fillers show great advantages in their applications in flexible electronic devices. However, integratable high-sensitivity pressure sensors remain understudied. This work improves the conductivity and sensitivity of PDMS-Fe/Ni piezoresistive composites by introducing silver flakes and magnetic-assisted alignment techniques. As secondary fillers, silver flakes with high aspect ratios enhance the conductive percolation network in composites. Meanwhile, a magnetic field aligns ferromagnetic particles to further improve the conductivity and sensitivity of composites. The resistivity of the composite decreases sharply by 1000 times within a tiny compression strain of 1%, indicating excellent sensing performance. On the basis of this, we demonstrate an integratable miniature pressure sensor with a small size (2 × 2 × 1 mm), high sensitivity (0.966 kPa−1), and wide sensing range (200 kPa). Finally, we develop a flexible E-skin system with 5 × 5 integratable sensor units to detect pressure distribution, which shows rapid real-time response, high resolution, and high sensitivity.
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Li, Rui, Xin Gou, Xinyan Li, Hainuo Wang, Haibo Ruan, Yuting Xiong, Xianlun Tang, Yuanyuan Li i Ping-an Yang. "Improved Stretchable and Sensitive Fe Nanowire-Based Strain Sensor by Optimizing Areal Density of Nanowire Network". Molecules 27, nr 15 (23.07.2022): 4717. http://dx.doi.org/10.3390/molecules27154717.
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Flexible strain sensors, when considering high sensitivity and a large strain range, have become a key requirement for current robotic applications. However, it is still a thorny issue to take both factors into consideration at the same time. Here, we report a sandwich-structured strain sensor based on Fe nanowires (Fe NWs) that has a high GF (37–53) while taking into account a large strain range (15–57.5%), low hysteresis (2.45%), stability, and low cost with an areal density of Fe NWs of 4.4 mg/cm2. Additionally, the relationship between the contact point of the conductive network, the output resistance, and the areal density of the sensing unit is analyzed. Microscopically, the contact points of the conductive network directly affect the sensor output resistance distribution, thereby affecting the gauge factor (GF) of the sensor. Macroscopically, the areal density and the output resistivity of the strain sensor have the opposite percolation theory, which affects its linearity performance. At the same time, there is a positive correlation between the areal density and the contact point: when the stretching amount is constant, it theoretically shows that the areal density affects the GF. When the areal density reaches this percolation threshold range, the sensing performance is the best. This will lay the foundation for rapid applications in wearable robots.
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Azhari, Faezeh, i Nemkumar Banthia. "A 3D percolation model for conductive fibrous composites: application in cement-based sensors". Journal of Materials Science 50, nr 17 (5.06.2015): 5817–21. http://dx.doi.org/10.1007/s10853-015-9129-3.
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Mu, Quanyi, Ting Hu, Xinya Tian, Tongchuan Li i Xiao Kuang. "The Effect of Filler Dimensionality and Content on Resistive Viscoelasticity of Conductive Polymer Composites for Soft Strain Sensors". Polymers 15, nr 16 (11.08.2023): 3379. http://dx.doi.org/10.3390/polym15163379.
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Soft strain sensors based on conductive polymer composites (CPCs) provide a simple and feasible detection tool in wearable electronics, soft machines, electronic skin, etc. However, the CPCs-based soft strain sensors exhibit resistive viscoelasticity (or time-dependent properties) that hinder the intuitive reflection of the accurate strain and a simple calibration process. In this paper, CPCs with different carbon nanotubes (CNTs) and carbon black (CB) contents were prepared, and electro-mechanical experiments were conducted to study the effect of filler dimensionality and content on the resistive viscoelasticity of CPCs, aimed at guiding the fabrication of CPCs with low resistive viscoelasticity. Furthermore, resistive viscoelasticity and mechanical viscoelasticity were compared to study the origin of the resistive viscoelasticity of CPCs. We found that, at the vicinity of their percolation threshold, the CPCs exhibit high resistive viscoelasticity despite their high sensitivity. In addition, the secondary peaks for CB/SR composite were negligible when the CB concentration was low. Generally, compared with one-dimensional CNT-filled CPCs, the zero-dimensional CB-filled CPCs show higher sensitivity, lower resistive hysteresis, lower resistance relaxation ratio, and better cyclic performance, so they are more suitable for sensor usage. By comparing the resistive viscoelasticity and mechanical viscoelasticity of CPCs, it is indicated that, when the concentration of nanoparticles (NPs) approaches the percolation thresholds, the resistive viscoelasticity is mainly derived from the change of conductive network, while when the concentration of NPs is higher, it is primarily due to the unrecoverable deformations inside the material.
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Bree, Gerard, Hongqing Hao, Zlatka Stoeva i Chee Tong John Low. "Monitoring state of charge and volume expansion in lithium-ion batteries: an approach using surface mounted thin-film graphene sensors". RSC Advances 13, nr 10 (2023): 7045–54. http://dx.doi.org/10.1039/d2ra07572e.
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Mersch, Johannes, Henriette Probst, Andreas Nocke, Chokri Cherif i Gerald Gerlach. "Non-Monotonic Sensor Behavior of Carbon Particle-Filled Textile Strain Sensors". Engineering Proceedings 6, nr 1 (17.05.2021): 13. http://dx.doi.org/10.3390/i3s2021dresden-10140.
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Carbon particle-filled elastomers are a widely researched option to be used as piezoresistive strain sensors for soft robotics or human motion monitoring. Therefore, various polymers can be compounded with carbon black (CB), carbon nanotubes (CNT) or graphene. However, in many studies, the electrical resistance strain response of the carbon particle-filled elastomers is non-monotonic in dynamic evaluation scenarios. The non-monotonic material behavior is also called shoulder phenomenon or secondary peak. Until today, the underlying cause is not sufficiently well understood. In this study, several influencing test parameters on the shoulder phenomena are explored, such as strain level, strain rate and strain history. Moreover, material parameters such as CNT content and anisotropy are varied in melt-spun CNT filled thermoplastic polyurethane (TPU) filament yarns, and their non-monotonic sensor response is evaluated. Additionally, a theoretical concept for the underlying mechanism and thereupon-based model is presented. An equivalent circuit model is used, which incorporates the visco-elastic properties and the characteristic of the percolation network formed by the conductive filler material. The simulation results are in good agreement when compared to the experimental results.
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Cho, Chia-Yu, Jui-Chen Chang, Min-Xian Cai, Pei-Ting Lin i Yao-Joe Yang. "Dewetting Process of Silver Thin Films and Its Application on Percolative Pressure Sensors with High Sensitivity". Polymers 15, nr 1 (30.12.2022): 180. http://dx.doi.org/10.3390/polym15010180.
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This work reports on an innovative dewetting process of silver thin films to realize percolative nanoparticle arrays (NPAs) and demonstrates its application on highly sensitive pressure sensors. The dewetting process, which is a simple and promising technique, synthesizes NPAs by breaking the as-deposited metal film into randomly distributed islands. The NPA properties, such as the mean particle size and the spacing between adjacent particles, can be easily tailored by controlling the dewetting temperature, as well as the as-deposited metal-film thickness. The fabricated NPAs were employed to develop gauge pressure sensors with high sensitivity. The proposed sensor consists of a sealed reference-pressure cavity, a polyimide (PI) membrane patterned with an interdigital electrode pair (IEP), and a silver NPA deposited on the IEP and the PI membrane. The operational principle of the device is based on the NPA percolation effect with deformation-dependence. The fabricated sensors exhibit rapid responses and excellent linearity at around 1 atm. The maximum sensitivity is about 0.1 kPa−1. The advantages of the proposed devices include ultrahigh sensitivity, a reduced thermal disturbance, and a decreased power consumption. A practical application of this pressure sensor with high resolution was demonstrated by using it to measure the relative floor height of a building.
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Afik, Noa, Omri Yadgar, Anastasiya Volison-Klimentiev, Sivan Peretz-Damari, Avia Ohayon-Lavi, Amr Alatawna, Gal Yosefi, Ronit Bitton, Naomi Fuchs i Oren Regev. "Sensing Exposure Time to Oxygen by Applying a Percolation-Induced Principle". Sensors 20, nr 16 (10.08.2020): 4465. http://dx.doi.org/10.3390/s20164465.
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The determination of food freshness along manufacturer-to-consumer transportation lines is a challenging problem that calls for cheap, simple, reliable, and nontoxic sensors inside food packaging. We present a novel approach for oxygen sensing in which the exposure time to oxygen—rather than the oxygen concentration per se—is monitored. We developed a nontoxic hybrid composite-based sensor consisting of graphite powder (conductive filler), clay (viscosity control filler) and linseed oil (the matrix). Upon exposure to oxygen, the insulating linseed oil is oxidized, leading to polymerization and shrinkage of the matrix and hence to an increase in the concentration of the electrically conductive graphite powder up to percolation, which serves as an indicator of food spoilage. In the developed sensor, the exposure time to oxygen (days to weeks) is obtained by measuring the electrical conductivity though the sensor. The sensor functionality could be tuned by changing the oil viscosity, the aspect ratio of the conductive filler, and/or the concentration of the clay, thereby adapting the sensor to monitoring the quality of food products with different sensitivities to oxygen exposure time (e.g., fish vs grain).
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Melo, Diego S., Idalci C. Reis, Júlio C. Queiroz, Cicero R. Cena, Bacus O. Nahime, José A. Malmonge i Michael J. Silva. "Evaluation of Piezoresistive and Electrical Properties of Conductive Nanocomposite Based on Castor-Oil Polyurethane Filled with MWCNT and Carbon Black". Materials 16, nr 8 (19.04.2023): 3223. http://dx.doi.org/10.3390/ma16083223.
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Flexible films of a conductive polymer nanocomposite-based castor oil polyurethane (PUR), filled with different concentrations of carbon black (CB) nanoparticles or multiwall carbon nanotubes (MWCNTs), were obtained by a casting method. The piezoresistive, electrical, and dielectric properties of the PUR/MWCNT and PUR/CB composites were compared. The dc electrical conductivity of both PUR/MWCNT and PUR/CB nanocomposites exhibited strong dependences on the concentration of conducting nanofillers. Their percolation thresholds were 1.56 and 1.5 mass%, respectively. Above the threshold percolation level, the electrical conductivity value increased from 1.65 × 10−12 for the matrix PUR to 2.3 × 10−3 and 1.24 × 10−5 S/m for PUR/MWCNT and PUR/CB samples, respectively. Due to the better CB dispersion in the PUR matrix, the PUR/CB nanocomposite exhibited a lower percolation threshold value, corroborated by scanning electron microscopy images. The real part of the alternating conductivity of the nanocomposites was in accordance with Jonscher’s law, indicating that conduction occurred by hopping between states in the conducting nanofillers. The piezoresistive properties were investigated under tensile cycles. The nanocomposites exhibited piezoresistive responses and, thus, could be used as piezoresistive sensors.
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Cao, Zhou, Liao, Yang, Pan, Li, Pang, Zhou i Su. "A Spray-on, Nanocomposite-Based Sensor Network for in-Situ Active Structural Health Monitoring". Sensors 19, nr 9 (4.05.2019): 2077. http://dx.doi.org/10.3390/s19092077.
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A new breed of nanocomposite-based spray-on sensor is developed for in-situ active structural health monitoring (SHM). The novel nanocomposite sensor is rigorously designed with graphene as the nanofiller and polyvinylpyrrolidone (PVP) as the matrix, fabricated using a simple spray deposition process. Electrical analysis, as well as morphological characterization of the spray-on sensor, was conducted to investigate percolation characteristic, in which the optimal threshold (~0.91%) of the graphene/PVP sensor was determined. Owing to the uniform and stable conductive network formed by well-dispersed graphene nanosheets in the PVP matrix, the tailor-made spray-on sensor exhibited excellent piezoresistive performance. By virtue of the tunneling effect of the conductive network, the sensor was proven to be capable of perceiving signals of guided ultrasonic waves (GUWs) with ultrahigh frequency up to 500 kHz. Lightweight and flexible, the spray-on nanocomposite sensor demonstrated superior sensitivity, high fidelity, and high signal-to-noise ratio under dynamic strain with ultralow magnitude (of the order of micro-strain) that is comparable with commercial lead zirconate titanate (PZT) wafers. The sensors were further networked to perform damage characterization, and the results indicate significant application potential of the spray-on nanocomposite-based sensor for in-situ active GUW-based SHM.
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Sedova, A., S. Khodorov, D. Ehre, B. Achrai, H. D. Wagner, R. Tenne, H. Dodiuk i S. Kenig. "Dielectric and Electrical Properties of WS2 Nanotubes/Epoxy Composites and Their Use for Stress Monitoring of Structures". Journal of Nanomaterials 2017 (2017): 1–13. http://dx.doi.org/10.1155/2017/4838095.
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The dielectric and electrical characteristics of the semiconductive WS2 nanotubes/epoxy composites were studied as a function of the nanotubes concentration and the pressure applied during their molding. In addition, the ability of WS2 nanotubes to serve as stress sensors in epoxy based nanocomposites, for health-monitoring applications, was studied. The nanocomposite elements were loaded in three-point bending configuration. The direct current was monitored simultaneously with stress-strain measurements. It was found that, in nanocomposites, above the percolation concentrations of the nanotubes, the electrical conductivity increases considerably with the applied load and hence WS2 nanotubes can be potentially used as sensors for health monitoring of structural components.
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Kruse, Peter. "(Invited) Chemiresistive Water Quality Sensors: Challenges and Progress". ECS Meeting Abstracts MA2022-01, nr 52 (7.07.2022): 2135. http://dx.doi.org/10.1149/ma2022-01522135mtgabs.
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Chemiresistors are solid state devices that change their electronic properties (more specifically, the resistance of a conductive thin film or percolation network) as a result of chemical interactions with their environment. They are a well-established and widely commercialized technology for gas or vapor sensor applications. The active layer may consist of metal oxides, polymers, nanomaterials or composites. In most cases, chemisorption or catalytic activity involving the analyte results in surface doping of the active layer, although other mechanisms (such as conductivity changes due to swelling) have also been reported. A significant part of the sensing literature is taken up by reports of ChemFETs, in which case the conductivity of the active layer can also be modulated by an applied gate voltage. Gate voltage modulation is helpful for establishing the sensing mechanism and - on occasion - for distinguishing multiple simultaneous target analytes. In most cases, however, the actual sensor operation occurs at zero gate voltage, thus reducing the ChemFET to a chemiresistor. [1] Gas sensors can be operated at high voltages and without shielding the contacts to the film from gas exposure, two simplifications that are not afforded to sensors operating in aqueous environments. Water quality sensors are a surprisingly underserved area of sensor applications.[2] Important chemical water quality parameters include pH, dissolved gases, common ions and a range of toxic trace contaminants which may be ionic or uncharged, inorganic or organic. All these water quality parameters are usually monitored using colorimetric sensors, electrochemical sensors and large lab-based instruments. None of these lend themselves to low maintenance, reagent free, low power continuous operation for online monitoring. In particular, colorimetric sensors need a resupply of reagents and electrochemical sensors require reference electrodes. Chemiresistors have the potential to eliminate all these disadvantages, but there has been slow progress in adapting them to aqueous analytes. They are simple and economical to manufacture, and can operate reagent-free and with low or no maintenance. Unlike electrochemical sensors they do not require reference electrodes. Challenges include the need to prevent electrical shorts through the aqueous medium and the need to keep the sensing voltage low enough to avoid electrochemical reactions at the sensor. We have built a chemiresistive sensing platform for aqueous media. The active sensor element consists of a percolation network of low-dimensional materials particles that form a conducting film, e.g. from carbon nanotubes, pencil trace, exfoliated graphene or MoS2. The first members of that platform were free chlorine sensors,[3-5] but we have also demonstrated pH sensitive films [6,7] and cation sensors.[8] While there are some challenges associated with expanding the range of accessible analytes,[9] we have recently expanded the applicability of our platform, in particular anions and cations that are commonly present as pollutants in surface and drinking water. Our sensors can be incorporated into a variety of systems and will also be suitable for online monitoring in remote and resource-poor locations. References: [1] A. Zubiarrain-Laserna and P. Kruse, Graphene-Based Water Quality Sensors. J. Electrochem. Soc. 167 (2020) 037539. [2] P. Kruse, Review on Water Quality Sensors. J. Phys. D 51 (2018) 203002. [3] L. H. H. Hsu, E. Hoque, P. Kruse, and P. R. Selvaganapathy, A carbon nanotube based resettable sensor for measuring free chlorine in drinking water. Appl. Phys. Lett. 106 (2015) 063102. [4] E. Hoque, L. H. H. Hsu, A. Aryasomayajula, P. R. Selvaganapathy, and P. Kruse, Pencil-Drawn Chemiresistive Sensor for Free Chlorine in Water. IEEE Sens. Lett. 1 (2017) 4500504. [5] A. Mohtasebi, A. D. Broomfield, T. Chowdhury, P. R. Selvaganapathy, and P. Kruse, Reagent-Free Quantification of Aqueous Free Chlorine via Electrical Readout of Colorimetrically Functionalized Pencil Lines. ACS Appl. Mater. Interfaces 9 (2017) 20748-20761. [6] D. Saha, P. R. Selvaganapathy and P. Kruse, Peroxide-Induced Tuning of the Conductivity of Nanometer-Thick MoS2 Films for Solid State Sensors. ACS Appl. Nano Mater. 3 (2020) 10864-10877. [7] S. Angizi, E. Y. C. Yu, J. Dalmieda, D. Saha, P. R. Selvaganapathy and P. Kruse, Defect Engineering of Graphene to Modulate pH Response of Graphene Devices. Langmuir 37 (2021) 12163-12178. [8] J. Dalmieda, A. Zubiarrain-Laserna, D. Ganepola, P. R. Selvaganapathy and P. Kruse, Chemiresistive Detection of Silver Ions in Aqueous Media. Sens. Actuators B:Chem 328 (2021) 129023. [9] J. Dalmieda, A. Zubiarrain-Laserna, D. Saha, P. R. Selvaganapathy and P. Kruse, Impact of Surface Adsorption on Metal-Ligand Binding of Phenanthrolines. J. Phys. Chem. C 125 (2021) 21112-21123. Figure 1
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Noh, Ji-Yeon, Mirae Kim i Jong-Man Kim. "Effect of Metal Film Thickness on Strain-Sensing Performance of Crack-Based Stretchable Hybrid Piezoresistive Electrode". Korean Journal of Metals and Materials 60, nr 12 (5.12.2022): 933–39. http://dx.doi.org/10.3365/kjmm.2022.60.12.933.
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In recent decades, many research efforts have been devoted to developing high-performance stretchable strain sensors due to their potential for application in various emerging wearable sensor systems. This work presents a facile yet highly efficient way of modulating the sensing performance of a thin metal film/conductive composite hybrid piezoresistor-based stretchable strain sensor by simply controlling the metal film thickness. The hybrid strain sensor can be simply fabricated by sputtering a thin platinum (Pt) film onto a silver nanowire (AgNW)/dragon skin (DS) composite substrate prepared via a facile embed-and-transfer process in a reproducible manner. The density of the network-shaped mechanical crack induced in the Pt film tended to decrease with increasing the Pt thickness, thereby leading to a higher gauge factor of the sensor. The fabricated hybrid strain sensor also exhibited a large stretchability of 150% owing to its electrical robustness under strain, based on the unique morphology, formed of the network-shaped Pt crack and AgNW percolation network embedded in the DS matrix. Thanks to the balanced strain-sensing performance of the hybrid strain sensor in conjunction with large stretchability, the device was successfully demonstrated as a wearable human-activity monitoring solution that can monitor a wide range of human motions in real time.
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Seitz, Christoph, Giuliana Beck, Jörg Hennemann, Christian Kandzia, Karl P. Hering, Angelika Polity, Peter J. Klar i in. "H<sub>2</sub>S dosimeter with controllable percolation threshold based on semi-conducting copper oxide thin films". Journal of Sensors and Sensor Systems 6, nr 1 (2.05.2017): 163–70. http://dx.doi.org/10.5194/jsss-6-163-2017.
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Abstract. Copper oxides, such as CuO and Cu2O, are promising materials for H2S detection because of the reversible reaction with H2S to copper sulfides (CuS, Cu2S). Along with the phase change, the electrical conductance increases by several orders of magnitude. On CuOx films the H2S reaction causes the formation of statistically distributed CuxS islands. Continuous exposition to H2S leads to island growth and eventually to the formation of an electrical highly conductive path traversing the entire system: the so-called percolation path. The associated CuOx ∕ CuxS conversion ratio is referred to as the percolation threshold. This pronounced threshold causes a gas concentration dependent switch-like behaviour of the film conductance. However, to utilize this effect for the preparation of CuO-based H2S sensors, a profound understanding of the operational and morphological parameters influencing the CuS path evolution is needed.Thus, this article is focused on basic features of H2S detection by copper oxide films and the influence of structural parameters on the percolation threshold and switching behaviour. In particular, two important factors, namely the stoichiometry of copper oxides (CuO, Cu2O and Cu4O3) and surface morphology, are investigated in detail. CuOx thin films were synthesized by a radio frequency magnetron sputtering process which allows modification of these parameters. It could be shown that, for instance, the impact on the switching behaviour is dominated by morphology rather than stoichiometry of copper oxide.
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Chen, Bailiang, Ying Liu, Guishan Wang, Xianzhe Cheng, Guanjun Liu, Jing Qiu i Kehong Lv. "Low-Cost Flexible Strain Sensor Based on Thick CVD Graphene". Nano 13, nr 11 (listopad 2018): 1850126. http://dx.doi.org/10.1142/s1793292018501266.
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Flexible strain sensors, as the core member of the family of smart electronic devices, along with reasonable sensing range and sensitivity plus low cost, have rose a huge consumer market and also immense interests in fundamental studies and technological applications, especially in the field of biomimetic robots movement detection and human health condition monitoring. In this paper, we propose a new flexible strain sensor based on thick CVD graphene film and its low-cost fabrication strategy by using the commercial adhesive tape as flexible substrate. The tensile tests in a strain range of [Formula: see text]30% were implemented, and a gage factor of 30 was achieved under high strain condition. The optical microscopic observation with different strains showed the evolution of cracks in graphene film. Together with commonly used platelet overlap theory and percolation network theory for sensor resistance modeling, we established an overlap destructive resistance model to analyze the sensing mechanism of our devices, which fitted the experimental data very well. The finding of difference of fitting parameters in small and large strain ranges revealed the multiple stage feature of graphene crack evolution. The resistance fallback phenomenon due to the viscoelasticity of flexible substrate was analyzed. Our flexible strain sensor with low cost and simple fabrication process exhibits great potential for commercial applications.
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Zhu, Bicheng, Thomas Kerr-Philips, Zahraa Al Ghaus, Eddie Wai Chi Chan, David Barker, Clive W. Evans, David E. Williams i Jadranka Travas-Sejdic. "Ultra-Highly Sensitive DNA Detection with Conducting Polymer-Modified Electrodes: Mechanism, Manufacture and Prospects for Rapid e-PCR". Journal of The Electrochemical Society 169, nr 3 (1.03.2022): 037521. http://dx.doi.org/10.1149/1945-7111/ac5ced.
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At low copy number, sequence detection by polymerase chain reaction (PCR) requires up to 30 cycles (amplification 109) to produce a reliably detectable concentration of fluorescently-labelled amplicons. The cycle number and hence detection time is determined by the analytical sensitivity of the detector. Hybridisation of complementary DNA strands to oligonucleotide-modified conducting polymer electrodes yields an increase in the charge transfer resistance for the ferri-ferrocyanide redox couple. We demonstrate sensors using screen-printed carbon electrodes modified with a conducting polymer formed from a monomer pre-functionalised with complementary oligonucleotide, with pM sensitivity for short sequences and aM for bacterial lysate, with a response time-scale of 5 min. The response is due to the variation of electrical resistance within the polymer film. We develop a mechanism based on repulsion from the solution interface of dopant anions by the charge associated with surface-bound DNA. With results for >160 single-use sensors, we formulate a response model based on percolation within a random resistor network and highlight challenges for large-scale manufacture of such sensors. Such sensors used for label-free electrochemical detection for PCR (e-PCR) would decrease the required cycle number from 30 to less than 10 and would offer a much simplified instrument construction.
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Naik, Aparimita Priyadarshini, i Sreeja Pekkat. "Determination of wetting soil water characteristics curve from disk infiltrometer measurements". E3S Web of Conferences 382 (2023): 25006. http://dx.doi.org/10.1051/e3sconf/202338225006.
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A wetting soil water characteristic curve (SWCCw) is necessary for understanding and interpreting the re-distribution of infiltrated rainwater, percolation rate, and contaminant transport. Direct determination of SWCCw is tedious and needs destructive sampling and invasive sensor installation. This study demonstrates an indirect method for determining SWCCw based on infiltration measurements using a mini disc infiltrometer (MDI). Under controlled initial conditions, infiltration tests were conducted, coupled with real-time soil moisture and matric potential measurements using sensors. Sensor data facilitated assessment and cross-verification of SWCCw indirectly determined from MDI measurements. The indirect estimation involved inverse analysis and optimization of SWCCw parameters (α and n of the van Genuchten model) based on measured cumulative infiltration (CI) -versus-time response along with the knowledge of final volumetric water content (VWCf). The optimized SWCCw from MDI-infiltration matched the sensor-measured SWCCw reasonably well. The statistical tests using ANOVA proved that the CI measurements from MDI, together with VWCf information, are reliable input for inverse estimation of SWCCw and its parameters. Based on a realistic wetting process in the unsaturated zone beneath the disc infiltrometer, this study demonstrates the utility of a compact MDI for a quick, non-destructive measurement of SWCCw.
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Moskalyuk, Olga, Diana Vol‘nova i Ekaterina Tsobkallo. "Modeling of the Electrotransport Process in PP-Based and PLA-Based Composite Fibers Filled with Carbon Nanofibers". Polymers 14, nr 12 (11.06.2022): 2362. http://dx.doi.org/10.3390/polym14122362.
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Polypropylene and polylactide-based composite fibers have been produced by a melt technology. Long vapor-grown carbon fibers (CNFs) have been used as electrical conductivity fillers. It is clearly shown by experimental methods that the CNFs are evenly distributed in the polymer matrix, orienting themselves along the direction of fiber extrusion and retaining their initial dimensions. It is shown that for composites fibers based on crystallizing (polypropylene) and amorphous (polylactide acid) polymer matrix, the dependence of electrical resistance on the filler concentration is percolation character and can be described as a double Boltzmann function. Four sections are identified on the dependences of the electrical resistance on the filler concentration for composite fibers, and the reasons for this character of this dependence on the formation of electrically conductive circuits are analyzed. Investigated in this work are the PP-based and PLA-based composites filled with carbon nanofibers that can be used as antistatic, shielding materials, or as sensors.
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MOHAMMADI, HOSSEIN, EHSAN NEDAAEE OSKOEE, MOHSEN AFSHARCHI, NASSER YAZDANI i MUHAMMAD SAHIMI. "A PERCOLATION MODEL OF MOBILE AD-HOC NETWORKS". International Journal of Modern Physics C 20, nr 12 (grudzień 2009): 1871–902. http://dx.doi.org/10.1142/s0129183109014795.
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Mobile ad-hoc networks (MANETs) are random, self-configurable and rapidly-deployable networks. The main goal of developing the MANETs is not only obtaining better service, but also having networks that can serve in situations in which no other means of communications can operate. Examples include networks that are used in battlefields, in search-and-rescue operations, and networks of sensors. We propose a percolation model for studying the properties of the MANETs. The model is based on a random network of sites, distributed in space, which represent the mobile nodes. Two nodes are linked if they are within each other's transmission ranges. A node may be lost or become inactive if, for example, it runs out of energy (provided by its batteries). A link can be lost if, for example, one of its two end nodes moves outside of the other's transmission range. Extensive Monte Carlo simulations are carried out to study the properties of the model. The network's topology is characterized by a critical transmission range, which is the analogue of the percolation threshold. It is shown that not only can the model take into account several important features of the real MANETs and explain them in physical terms, but also leads to the development of efficient protocols for self-configuration, adaptability, and disaster survival, which are of utmost importance to the practical applications.
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Patel, Vinay, Peter Kruse i P. Ravi Selvaganapathy. "An Electropolymerized Self Assembled Monolayer of Crystal Violet for Chemiresistive Hydrogen Peroxide Sensor". ECS Meeting Abstracts MA2021-02, nr 57 (19.10.2021): 1919. http://dx.doi.org/10.1149/ma2021-02571919mtgabs.
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Chemiresistive sensors have been widely used for gas sensing but recently few studies have reported their use in liquids. Unlike electrochemical sensors, these sensors are simple to fabricate and operate with a single sensing film electrodes with two electrical contacts for monitoring change in current under a small potential bias, without the need of reference electrode. Hydrogen peroxide (H2O2) is an intermediate molecule generated in numerous peroxidase assays. Therefore, it is widely used for detecting multiple biomolecules like glucose, galactose etc. H2O2 detection is commonly performed using colorimetric and electrochemical sensors. However, colorimetric sensors require chemicals while electrochemical sensors need reference electrode for reliable measurements [1]. Here, we demonstrated a reagent less H2O2 sensor fabricated using carbon nanotube (CNT) as the base substrate and an electropolymerized self assembled monolayer crystal violet as selective ligand. The functionalised 2D percolation network of CNT film transduces a selective response for H2O2. The chemiresistive sensor was fabricated using a low-cost xurography based fabrication process. The CNT dispersion was supplied by Nano-C, Inc. A diluted CNT dispersion (4% v/v) was prepared by sonicating the CNT ink in a mixture of methanol and water (1:1) for 15 minutes in a bath sonicator. The diluted CNT dispersion was drop casted on a frosted glass substrate and cured at 120 oC for 60 minutes. Patterned gold leaf was used as the contact electrodes and copper tape was used for the external electrode (Figure 1a). The sensor fabrication process is described in details elsewhere [2]. The electrodes were functionalized with a self assembled monolayer by immersing them in 0.6 mM crystal violet prepared in 0.1 M phosphate buffer for 90 minutes. Then, the self assembled monolayer of crystal violet was electropolymerized using cyclic voltammetry from 0 to 2V and scan rate of 0.1 V/s. The sensor response was tested in five different H2O2 concentrations (0.5 ppm, 5 ppm, 50 ppm, 500 ppm, and 1000 ppm). H2O2 solutions were prepared by diluting the stock solution in 39 mM acetate buffer similar to the buffer strength of blood. The sensor response for various H2O2 concentrations is shown in Figure 1b. The sensor response for each H2O2 solution was calculated with 39 mM acetate buffer as the baseline. Each bar graph represents the average of last-minute current measurements of a 30 minutes run. The sensor exhibited an increase in current value with increase in H2O2 concentration from 0.5 ppm to 1000 ppm. The crystal violet attached on the CNT film undergoes oxidation in presence of H2O2 concentration. The change in oxidation state of crystal violet resulted alterations in doping level of functionalized CNT network leading to a change in conductivity of the sensor. No significant interference was observed for common interferents like as glucose, galactose, urea, uric acid and gluconic acid. The sensor was also chemically reset using 0.1 M ascorbic acid by reducing the oxidized crystal violet. We demonstrated that an electropolymerized self assembled monolayer of crystal violet attached to CNT can measure H2O2 concentration within a range of 0.5 ppm to 1000 ppm. In addition, the low-cost fabrication process and the peroxide sensor enables this technology to a wide range of peroxidase based enzymatic assays that are biological relevant both in medical diagnostics biological research. References [1] V. Patel, P. Kruse, P.R. Selvaganapathy, Solid State Sensors for Hydrogen Peroxide Detection, Biosensors. 11 (2020) 1–32. https://doi.org/10.3390/bios11010009. [2] V. Patel, P. Kruse, P.R. Selvaganapathy, Flexible chemiresistive sensor with xurographically patterned gold leaf as contact electrodes for measuring free chlorine, (2021) 1–4. https://doi.org/10.1109/fleps51544.2021.9469787. Figure 1
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Faupel, Franz, Vladimir Zaporojtchenko, Thomas Strunskus, Henry Greve, Ulrich Schürmann, Haile Takele, Christian Hanisch i in. "Functional Polymer Nanocomposites". Polymers and Polymer Composites 16, nr 8 (październik 2008): 471–81. http://dx.doi.org/10.1177/096739110801600801.
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While extensive research has been carried out in the field of structural polymer-based nanocomposites much less investigations have been concerned with polymer nanocomposites for functional applications. Among the functional nanomaterials, nanocomposites consisting of metal nanoparticles dispersed in a dielectric matrix are of particular interest due to their novel functional properties offering hosts of new applications. Here, polymers are attractive as matrix, and several approaches have been reported to incorporate metal nanoparticles into polymers. The present review is concerned with the preparation of polymer-based nanocomposites by vapor phase co-and tandem deposition and the resulting functional properties. The techniques involve evaporation and sputtering, respectively, of metallic and organic components and inter alia allow the preparation of composites which contain alloy clusters of well defined composition. Emphasis is placed on soft-magnetic high frequency materials with cut-off frequencies well above 1 GHz and on optical composites with tuned plasmon resonances suitable for ultra thin color filters, Bragg reflectors, and other devices. In addition, antibacterial coatings and sensors for organic vapors are addressed. The latter take advantage of the steep drop of the electrical resistivity at the percolation threshold. First results are also reported on the incorporation of photo-switchable molecules into nanocomposites near the percolation threshold. Moreover, a novel approach to produce magnetic nanorods is presented.
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Maruani, Jonas, Isabelle Bruant, Frédéric Pablo i Laurent Gallimard. "Active vibration control of a smart functionally graded piezoelectric material plate using an adaptive fuzzy controller strategy". Journal of Intelligent Material Systems and Structures 30, nr 14 (6.06.2019): 2065–78. http://dx.doi.org/10.1177/1045389x19853628.
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In this article, the active vibration control of a smart structure made out of a single functionally graded piezoelectric material layer, equipped with a network of discrete electrodes, is studied. The material properties vary continuously across the direction of thickness, so that top and bottom surfaces consist of pure PZT4 and the mid surface is composed of pure aluminium. The percolation phenomenon is taken into account. A functionally graded piezoelectric material plate finite element based on the first-order shear deformation theory hypothesis and layer-wise approximation for electric potential is implemented. An optimization procedure is considered to define the relevant electrodes for actuators and sensors, based on controllable and observable criteria. An adaptative fuzzy controller system is used, activating with relevance the actuators according to the most excited eigenmodes. Simulations show the effectiveness of this kind of concept.
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Dios, Jose Ramon, Clara García-Astrain, Pedro Costa, Júlio César Viana i Senentxu Lanceros-Méndez. "Carbonaceous Filler Type and Content Dependence of the Physical-Chemical and Electromechanical Properties of Thermoplastic Elastomer Polymer Composites". Materials 12, nr 9 (30.04.2019): 1405. http://dx.doi.org/10.3390/ma12091405.
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Graphene, carbon nanotubes (CNT), and carbon nanofibers (CNF) are the most studied nanocarbonaceous fillers for polymer-based composite fabrication due to their excellent overall properties. The combination of thermoplastic elastomers with excellent mechanical properties (e.g., styrene-b-(ethylene-co-butylene)-b-styrene (SEBS)) and conductive nanofillers such as those mentioned previously opens the way to the preparation of multifunctional materials for large-strain (up to 10% or even above) sensor applications. This work reports on the influence of different nanofillers (CNT, CNF, and graphene) on the properties of a SEBS matrix. It is shown that the overall properties of the composites depend on filler type and content, with special influence on the electrical properties. CNT/SEBS composites presented a percolation threshold near 1 wt.% filler content, whereas CNF and graphene-based composites showed a percolation threshold above 5 wt.%. Maximum strain remained similar for most filler types and contents, except for the largest filler contents (1 wt.% or more) in graphene (G)/SEBS composites, showing a reduction from 600% for SEBS to 150% for 5G/SEBS. Electromechanical properties of CNT/SEBS composite for strains up to 10% showed a gauge factor (GF) varying from 2 to 2.5 for different applied strains. The electrical conductivity of the G and CNF composites at up to 5 wt.% filler content was not suitable for the development of piezoresistive sensing materials. We performed thermal ageing at 120 °C for 1, 24, and 72 h for SEBS and its composites with 5 wt.% nanofiller content in order to evaluate the stability of the material properties for high-temperature applications. The mechanical, thermal, and chemical properties of SEBS and the composites were identical to those of pristine composites, but the electrical conductivity decreased by near one order of magnitude and the GF decreased to values between 0.5 and 1 in aged CNT/SEBS composites. Thus, the materials can still be used as large-deformation sensors, but the reduction of both electrical and electromechanical response has to be considered.
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Thuau, Damien, Katherine Begley, Rishat Dilmurat, Abduleziz Ablat, Guillaume Wantz, Cédric Ayela i Mamatimin Abbas. "Exploring the Critical Thickness of Organic Semiconductor Layer for Enhanced Piezoresistive Sensitivity in Field-Effect Transistor Sensors". Materials 13, nr 7 (30.03.2020): 1583. http://dx.doi.org/10.3390/ma13071583.
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Organic semiconductors (OSCs) are promising transducer materials when applied in organic field-effect transistors (OFETs) taking advantage of their electrical properties which highly depend on the morphology of the semiconducting film. In this work, the effects of OSC thickness (ranging from 5 to 15 nm) on the piezoresistive sensitivity of a high-performance p-type organic semiconductor, namely dinaphtho [2,3-b:2,3-f] thieno [3,2–b] thiophene (DNTT), were investigated. Critical thickness of 6 nm thin film DNTT, thickness corresponding to the appearance of charge carrier percolation paths in the material, was demonstrated to be highly sensitive to mechanical strain. Gauge factors (GFs) of 42 ± 5 and −31 ± 6 were measured from the variation of output currents of 6 nm thick DNTT-based OFETs engineered on top of polymer cantilevers in response to compressive and tensile strain, respectively. The relationship between the morphologies of the different thin films and their corresponding piezoresistive sensitivities was discussed.
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Caradonna, Andrea, Claudio Badini, Elisa Padovano, Antonino Veca, Enea De Meo i Mario Pietroluongo. "Laser Treatments for Improving Electrical Conductivity and Piezoresistive Behavior of Polymer–Carbon Nanofiller Composites". Micromachines 10, nr 1 (18.01.2019): 63. http://dx.doi.org/10.3390/mi10010063.
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The effect of carbon nanotubes, graphene-like platelets, and another carbonaceous fillers of natural origin on the electrical conductivity of polymeric materials was studied. With the aim of keeping the filler content and the material cost as low as possible, the effect of laser surface treatments on the conductivity of polymer composites with filler load below the percolation threshold was also investigated. These treatments allowed processing in situ conductive tracks on the surface of insulating polymer-based materials. The importance of the kinds of fillers and matrices, and of the laser process parameters was studied. Carbon nanotubes were also used to obtain piezoresistive composites. The electrical response of these materials to a mechanical load was investigated in view of their exploitation for the production of pressure sensors and switches based on the piezoresistive effect. It was found that the piezoresistive behavior of composites with very low filler concentration can be improved with proper laser treatments.
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Bouhamed, Ayda, Nathanael Jöhrmann, Slim Naifar, Benny Böhm, Olav Hellwig, Bernhard Wunderle i Olfa Kanoun. "Collaborative Filler Network for Enhancing the Performance of BaTiO3/PDMS Flexible Piezoelectric Polymer Composite Nanogenerators". Sensors 22, nr 11 (31.05.2022): 4181. http://dx.doi.org/10.3390/s22114181.
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Wearable sensors are gaining attention in human health monitoring applications, even if their usability is limited due to battery need. Flexible nanogenerators (NGs) converting biomechanical energy into electrical energy offer an interesting solution, as they can supply the sensors or extend the battery lifetime. Herein, flexible generators based on lead-free barium titanate (BaTiO3) and a polydimethylsiloxane (PDMS) polymer have been developed. A comparative study was performed to investigate the impact of multiwalled carbon nanotubes (MWCNTs) via structural, morphological, electrical, and electromechanical measurements. This study demonstrated that MWCNTs boosts the performance of the NG at the percolation threshold. This enhancement is attributed to the enhanced conductivity that promotes charge transfer and enhanced mechanical property and piezoceramics particles distribution. The nanogenerator delivers a maximum open-circuit voltage (VOC) up to 1.5 V and output power of 40 nW, which is two times higher than NG without MWCNTs. Additionally, the performance can be tuned by controlling the composite thickness and the applied frequency. Thicker NG shows a better performance, which enlarges their potential use for harvesting biomechanical energy efficiently up to 11.22 V under palm striking. The voltage output dependency on temperature was also investigated. The results show that the output voltage changes enormously with the temperature.
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Esteves, David Seixas, Manuel F. C. Pereira, Ana Ribeiro, Nelson Durães, Maria C. Paiva i Elsa W. Sequeiros. "Development of MWCNT/Magnetite Flexible Triboelectric Sensors by Magnetic Patterning". Polymers 15, nr 13 (29.06.2023): 2870. http://dx.doi.org/10.3390/polym15132870.
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The fabrication of low-electrical-percolation-threshold polymer composites aims to reduce the weight fraction of the conductive nanomaterial necessary to achieve a given level of electrical resistivity of the composite. The present work aimed at preparing composites based on multiwalled carbon nanotubes (MWCNTs) and magnetite particles in a polyurethane (PU) matrix to study the effect on the electrical resistance of electrodes produced under magnetic fields. Composites with 1 wt.% of MWCNT, 1 wt.% of magnetite and combinations of both were prepared and analysed. The hybrid composites combined MWCNTs and magnetite at the weight ratios of 1:1; 1:1/6; 1:1/12; and 1:1/24. The results showed that MWCNTs were responsible for the electrical conductivity of the composites since the composites with 1 wt.% magnetite were non-conductive. Combining magnetite particles with MWCNTs reduces the electrical resistance of the composite. SQUID analysis showed that MWCNTs simultaneously exhibit ferromagnetism and diamagnetism, ferromagnetism being dominant at lower magnetic fields and diamagnetism being dominant at higher fields. Conversely, magnetite particles present a ferromagnetic response much stronger than MWCNTs. Finally, optical microscopy (OM) and X-ray micro computed tomography (micro CT) identified the interaction between particles and their location inside the composite. In conclusion, the combination of magnetite and MWCNTs in a polymer composite allows for the control of the location of these particles using an external magnetic field, decreasing the electrical resistance of the electrodes produced. By adding 1 wt.% of magnetite to 1 wt.% of MWCNT (1:1), the electric resistance of the composites decreased from 9 × 104 to 5 × 103 Ω. This approach significantly improved the reproducibility of the electrode’s fabrication process, enabling the development of a triboelectric sensor using a polyurethane (PU) composite and silicone rubber (SR). Finally, the method’s bearing was demonstrated by developing an automated robotic soft grip with tendon-driven actuation controlled by the triboelectric sensor. The results indicate that magnetic patterning is a versatile and low-cost approach to manufacturing sensors for soft robotics.
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Li, Wanchao, i Zeguang Pei. "Strain-sensing fiber with a core–sheath structure based on carbon black/polyurethane composites for smart textiles". Textile Research Journal 91, nr 15-16 (8.02.2021): 1907–23. http://dx.doi.org/10.1177/0040517521992355.
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Fiber-shaped sensors have great potential for real-time monitoring of human physiological signals thanks to the merging of electronic and textile technologies. This work reports on the fabrication of a core–sheath structured strain-sensing fiber based on the wet-spinning method. The sensing fiber is composed of a core of non-conducting polyurethane and a conducting sheath of carbon black in a polyurethane matrix. Microscopic observation reveals the irregular shape or scattered appearance of the core as well as the porous structure of the fiber, the diameter of which is in the range 200–500 μm. The electro-mechanical properties and their dependence on carbon black concentration in the sheath and draw ratio between the spinneret and first drafting roller are experimentally investigated. It has been found that the percolation threshold of the fiber is in the range 15–16 wt%. The resistance of the fiber rises stably as the fiber is stretched up to a strain of 120% and increases with the increase of draw ratio between the spinneret and first drafting roller. In the cyclic tensile tests, the resistance of the fiber exhibits good repeatability in subsequent loading–unloading cycles after pre-stretching, despite partial recovery of the resistance in the first few cycles. The integration of the strain-sensing fiber into textiles is demonstrated by the core-spun yarn fabricated based on a modified vortex spinning method. The results of this study indicate the fiber could be a promising candidate for a sensor for smart textiles.
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Monty-Bromer, Chelsea, Zachary Cheney, Shelby Daniels, Dunia Jaffal, Ruth Kurak, Orlando Lopez, Gabe Manzo, Mary Pat Nicodemus i Ronald Otterstetter. "(Invited) Carbon Nanotube-Based Fabric Sensor for Selective Sodium Detection in Sweat". ECS Meeting Abstracts MA2022-01, nr 8 (7.07.2022): 674. http://dx.doi.org/10.1149/ma2022-018674mtgabs.
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Despite the recent advancements in sensor detection of biomarkers in sweat, there is no sensor capable of long-term detection in constricted or load-bearing applications where other flexible plastic sensors might cause discomfort. In this work, a carbon nanotube-based fabric sensor capable of real-time detection of sodium in human sweat is presented. The sensor consists of an electrospun nylon-6 base functionalized with multi-walled carbon nanotubes for enhanced conductivity and p-tert-calix[4]arene for enhanced sodium selectivity. Monitoring sweat is a compelling choice to gain insight into a person’s hydration at a molecular level, as sweat is rich in physiological and metabolic information that can be obtained non-invasively. Body surface sweat is approximately 99% water but also contains over 40 other compounds, most notably the presence of extracellular ions: sodium and chloride. Sodium has been shown to have a notable correlation to body fluid balance and is lost in ample quantities during exercise, making it a promising candidate for the detection of dehydration (i.e., hypernatremia) and overhydration (i.e., hyponatremia). Other compounds commonly found in surface sweat include intracellular ions, metabolites, hormones, small proteins, and peptides. This rich composition and its correspondence to blood chemistry can be the key to accessing the body’s biomolecular (health) state through non-invasive monitoring and diagnostics. When monitoring biomarkers in sweat, the sampling step has the greatest impact on accuracy. Traditional methods for monitoring sweat sodium concentration involve collecting a sweat sample and performing chemical analysis in two separate steps. Typical sweat collection procedures include whole body washdown, sweat collection patches, arm bags, and Macroducts® which require some combination of tedious procedures, trained professionals, and large equipment for analysis. These methods are often limited by insufficient sample volumes, non-negligible sample evaporation, possible analyte degradation between sampling and analysis all of which strongly impacts the reliability and sensitivity of the measurement. To circumvent the problems caused by separating sampling and analysis, sweat sampling can also be completed using wearable sensors. Through in-situ sampling and analysis, wearable sweat sensors can perform the necessary real-time measurements with freshly generated sweat rather than a mixture of new and old sweat. Functional absorbent materials (e.g., paper, nonwoven, cellulosic, or hydrogels) are typically introduced between the skin and the sensing component; although as shown in this work, they can also be introduced as sensing components during sampling. The advantages of functional absorbent sensing materials are their low cost, multiple functions, real-time and continuous sensing, and most importantly the enhanced breathability of sweat glands. As such, these wearable sensors avoid the issue of altering the sweat composition underneath because they remove the old sweat accumulation as new sweat wicks into the material and washes away old sweat. This also allows physiological monitoring for longer periods of time than traditional epidermal microfluidic devices. Additionally, functional absorbent materials can also be integrated into fabrics with inherent moisture wicking properties to bring sweat to a sensing area. This work presents the characterization and on-body testing of a previously developed functional absorbent material sensor made of a multi-walled carbon nanotube (MWCNT) functionalized nylon-6 nanocomposite. The wearable-fabric sensor works by measuring resistance of the nanocomposite material as sodium binds to the sensor fabric. The functionalization of the nanocomposite material was verified by FTIR; while XRD spectra show that the electrospun nylon-6 is made of -form crystals and the resulting nanocomposite is intercalated/exfoliated with an increase in crystalline size. The optimized MWCNT/nylon-6 nanocomposite sensor has a MWCNT loading close to the percolation threshold at approximately 1-2 wt%. Experimental results demonstrated that the sensor is selective to sodium in sweat at a sensitivity of 10 mM sodium. When worn on the body (attached to human skin), the sensor is capable of real-time monitoring of sodium concentration in sweat in the physiologically relevant range of 10-110 mM with up to 95% accuracy. Additionally, the obtained signal can be sent out via Bluetooth so that changes in hydration status can be detected in real-time. Overall, this carbon nanotube-based fabric sensor can be integrated into “smarter” clothing to read an array of biomarkers in sweat. This could lead to better understanding of health and disease processes (e.g., analysis of common diabetic neurological complications, diagnosis of cystic fibrosis (CF), sweat monitoring for advanced prosthetic limb applications and bedridden patients, and athlete performance tracking) resulting in better treatments and health outcomes for all patients. Figure 1
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Park, Junghee, Jong-Sub Lee, Jongmuk Won i Jongchan Kim. "Evolution of Small Strain Soil Stiffness during Freeze-Thaw Cycle: Transition from Capillarity to Cementation Examined Using Magnetic and Piezo Crystal Sensors". Sensors 21, nr 9 (24.04.2021): 2992. http://dx.doi.org/10.3390/s21092992.
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Freeze-thaw cycles caused by seasonal temperature fluctuations significantly affect the geotechnical engineering properties. This study investigated the crucial role of water distribution patterns in the characterization of elastic wave properties for the fine F-110 sand during a freeze-thaw cycle. Sand specimens with four different water distribution patterns were prepared, namely homogeneously-mixed, evaporation-driven, vertically-, and horizontally-layered specimens. The P- and S-wave signatures of the specimens were monitored using piezo crystal sensors. Results indicated the criticality of water distribution patterns in the determination of small-strain soil properties even though the specimens had identical global water saturation. The nuclear magnetic resonance-based water volume depth profiles indicated that the evaporation-driven specimens had more heterogeneous pore-invasive ice-bonding layers at a high water saturation region; by contrast, the drying process facilitated uniform meniscuses around the particle contacts near the air percolation threshold. Elastic wave measurements for laboratory-prepared specimens might over/underestimate the small-strain soil stiffness of sediments in nature, wherein the drying processes prevailed to control the water saturation. This study highlighted a clear transition from capillary-controlled to cementation-controlled elastic wave properties during temperature oscillations.
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Podsiadły, Bartłomiej, Piotr Matuszewski, Andrzej Skalski i Marcin Słoma. "Carbon Nanotube-Based Composite Filaments for 3D Printing of Structural and Conductive Elements". Applied Sciences 11, nr 3 (30.01.2021): 1272. http://dx.doi.org/10.3390/app11031272.
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In this publication, we describe the process of fabrication and the analysis of the properties of nanocomposite filaments based on carbon nanotubes and acrylonitrile butadiene styrene (ABS) polymer for fused deposition modeling (FDM) additive manufacturing. Polymer granulate was mixed and extruded with a filling fraction of 0.99, 1.96, 4.76, 9.09 wt.% of CNTs (carbon nanotubes) to fabricate composite filaments with a diameter of 1.75 mm. Detailed mechanical and electrical investigations of printed test samples were performed. The results demonstrate that CNT content has a significant influence on mechanical properties and electrical conductivity of printed samples. Printed samples obtained from high CNT content composites exhibited an improvement in the tensile strength by 12.6%. Measurements of nanocomposites’ electrical properties exhibited non-linear relation between the supply voltage and measured sample resistivity. This effect can be attributed to the semiconductor nature of the CNT functional phase and the occurrence of a tunnelling effect in percolation network. Detailed I–V characteristics related to the amount of CNTs in the composite and the supply voltage influence are also presented. At a constant voltage value, the average resistivity of the printed elements is 2.5 Ωm for 4.76 wt.% CNT and 0.15 Ωm for 9.09 wt.% CNT, respectively. These results demonstrate that ABS/CNT composites are a promising functional material for FDM additive fabrication of structural elements, but also structural electronics and sensors.
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Thuau, Damien. "(Invited) Organic Thin Films Transistors: From Mechanical to Biochemical Sensors". ECS Meeting Abstracts MA2022-02, nr 35 (9.10.2022): 1287. http://dx.doi.org/10.1149/ma2022-02351287mtgabs.
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Interest in organic electronic materials, and in particular their potential for low-cost fabrication over large areas, led to the development of organic field-effect transistors (OFETs). The potential of OFETs has been demonstrated in a variety of applications, including pixel drivers for displays, bionic skin, wearable electronics and sensitive chemical sensors that can operate in aqueous environments. OFETs use conjugated, semiconducting small molecules and polymers and offer an alternative to inorganic devices for applications in which facile processing on different substrates and tunable electronic properties are required. The flexibility requirement implies either performance stability towards deformation, or conversely, detectable response to the deformation itself. The knowledge of the electromechanical response of organic semiconductors to external stresses is therefore not only interesting from a fundamental point of view, but also necessary for the development of real world applications. To this end, this presentation highlights the importance of the choice of functional materials (organic semiconductors and dielectrics) as well as the relationship structure/properties in transistors based sensors. Organic semiconductors (OSCs) are promising transducer materials when applied in OFETs taking advantage of their electrical properties that highly depend on the morphology of the semiconducting film. The effects of a high-performance p-type organic semiconductor, namely dinaphtho [2,3-b:2,3-f] thieno [3,2–b] thiophene (DNTT) thickness on its piezoresistive sensitivity are presented. A critical thickness corresponding to the appearance of charge carriers percolation paths in the material can tune the gauge factors (GFs) by a factor 10. In addition, single crystal OSC are regarded as promising electroactive materials for strain sensing application. Herein this talk, we will present how strain induces simultaneous mobility changes along all three axes, and that in some cases the response is higher along directions orthogonal to the mechanical deformation. These variations cannot be explained by the modulation of intermolecular distances, but only by a more complex molecular reorganisation, which is particularly enhanced, in terms of response, by p-stacking and herringbone stacking. This microscopic knowledge of the relation between structural and mobility variations is essential for the interpretation of electromechanical measurements for crystalline organic semiconductors, and for the rational design of electronic devices. Alternatively, this talk will highlight how the use of an active gate dielectric layer such as poly(vinylidenefluoride/trifluoroethylene) (P(VDF-TrFE)) piezoelectric polymer can lead to highly efficient electro-mechanical sensitivity. In such case, the sensing mechanism of the electro-mechanical transducer originates from the piezoelectric material itself, which affects the electrical behavior of the transistor as signature of a mechanical event. The second part of this talk will focus on another kind of TFT based sensor, namely the organic electrochemical transistors (OECTs) which have found recently applications in chemical and biological sensing and interfacing and neuromorphic computing. OECT rely on ions that are injected from the electrolyte into polymer-based mixed conductors, thereby changing its doping state and hence its conductivity. While great progress has been achieved, organic mixed conductors frequently experience significant volumetric changes during ion uptake/rejection, i.e., during doping/ de-doping and charging/discharging. Although ion dynamics may be enhanced in expanded networks, these volumetric changes can have undesirable consequences, e.g., negatively affecting hole/electron conduction and severely shortening device lifetime. New materials able to transport ions and electrons/holes and that exhibits low swelling will be presented, expanding the materials-design toolbox for the creation of low-swelling soft mixed conductors with tailored properties and applications in bioelectronics and beyond.
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Figueiredo, Nuno M., Ricardo Serra i Albano Cavaleiro. "Robust LSPR Sensing Using Thermally Embedded Au Nanoparticles in Glass Substrates". Nanomaterials 11, nr 6 (17.06.2021): 1592. http://dx.doi.org/10.3390/nano11061592.
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The poor adhesion and chemical and thermal stability of plasmonic nanostructures deposited on solid surfaces are a hindrance to the longevity and long-term development of robust localized surface plasmon resonance (LSPR)-based systems. In this paper, we have deposited gold (Au) nanolayers with thicknesses above the percolation limit over glass substrates and have used a thermal annealing treatment at a temperature above the substrate’s glass transition temperature to promote the dewetting, recrystallization, and thermal embedding of Au nanoparticles (NPs). Due to the partial embedding in glass, the NPs were strongly adherent to the surface of the substrate and were able to resist to the commonly used cleaning procedures and mechanical adhesion tests alike. The reflectivity of the embedded nanostructures was studied and shown to be strongly dependent on the NP size/shape distributions and on the degree of NP embedding. Strong optical scattering bands with increasing width and redshifted LSPR peak position were observed with the Au content. Refractive index sensitivity (RIS) values between 150 and 360 nm/RIU (concerning LSPR band edge shift) or between 32 and 72 nm/RIU (concerning LSPR peak position shift) were obtained for the samples having narrower LSPR extinction bands. These robust LSPR sensors can be used following a simple excitation/detection scheme consisting of a reflectance measurement at a fixed angle and wavelength.
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Tamburrano, Alessio, Alessandro Proietti, Marco Fortunato, Nicola Pesce i Maria Sabrina Sarto. "Exploring the Capabilities of a Piezoresistive Graphene-Loaded Waterborne Paint for Discrete Strain and Spatial Sensing". Sensors 22, nr 11 (2.06.2022): 4241. http://dx.doi.org/10.3390/s22114241.
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The development of a piezoresistive coating produced from dispersing graphene nanoplatelets (GNPs) inside a commercial water-based polyurethane paint is presented. The feasibility of its exploitation for realizing highly sensitive discrete strain sensors and to measure spatial strain distribution using linear and two-dimensional depositions was investigated. Firstly, the production process was optimized to achieve the best electromechanical response. The obtained materials were then subjected to different characterizations for structural and functional investigations. Morphological analyses showed a homogenous dispersion of GNPs within the host matrix and an average thickness of about 75 µm of the obtained nanostructured films. By several adhesion tests, it was demonstrated that the presence of the nanostructures inside the paint film lowered the adhesion strength by only 20% in respect to neat paint. Through electrical tests, the percolation curve of the nanomaterial was acquired, showing an effective electrical conductivity ranging from about 10−4 S/m to 3.5 S/m in relation to the different amounts of filler dispersed in the neat paint: in particular, samples with weight fractions of 2, 2.5, 3, 3.5, 4, 5 and 6 wt% of GNPs were produced and characterized. Next, the sensitivity to flexural strain of small piezoresistive sensors deposited by a spray-coating technique on a fiberglass-reinforced epoxy laminate beam was measured: a high gauge factor of 33 was obtained at a maximum strain of 1%. Thus, the sensitivity curve of the piezoresistive material was successively adopted to predict the strain along a multicontact painted strip on the same beam. Finally, for a painted laminate plate subjected to a mechanical flexural load, we demonstrated, through an electrical resistance tomography technique, the feasibility to map the electrical conductivity variations, which are strictly related to the induced strain/stress field. As a further example, we also showed the possibility of using the coating to detect the presence of conducting objects and damage.
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Khattab, Ezz El Deen, Hassan Sabet, Mostafa AbuBakr i Taher Hassan. "Multi-Sensor Remote Sensing Data and GIS Modeling for Mapping Groundwater Possibilities: A Case Study at the Western Side of Assiut Governorate, Egypt". Iraqi Geological Journal 56, nr 1C (31.03.2023): 176–90. http://dx.doi.org/10.46717/igj.56.1c.12ms-2023-3-23.
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Groundwater is an essential natural resource and it has a significant role in the development of dry lands. It is the main source of fresh water in arid and semi-arid regions. The present study investigates groundwater potentiality in the western part of Assiut Governorate, Egypt using advanced remote sensing and geospatial techniques along with hydrological data and field validation. The adopted method provides a low-cost and highly effective tool that can be combined with the conventional land-based approach for mapping Groundwater Potentiality. The study aims to determine the groundwater probability and recharging zones based on the contribution of some physiographic variables that influence groundwater storage. Therefore, multi-sensors remote sensing data from ASTER, Landsat-8, MODIS, Shuttle Radar Topography Mission (SRTM), Tropical Rainfall Measuring Mission (TRMM), and Radarsat-1 were accustomed to extract several geospatial thematic layers (variables). These layers include elevation, slope, curvature, drainage density, topographic wetness index, surface roughness, frequency of thermal anomaly, accumulated precipitation, Land Use/Land Cover (LULC), and lineament density. The produced layers are then scaled and weighted based on their contributions to the recharge of near-surface (unconfined) groundwater aquifers through infiltration and percolation processes. The Simple Additive Weight (SAW) method was utilized to aggregate all the weighted layers for creating the Groundwater Potentiality map. This aggregated grouped map was then classified into 5 classes, from very high to very low groundwater potentiality zones. The results show that the high Groundwater Potentiality was associated with low terrain, high surface ruggedness, high drainage and lineament densities, and relatively close to thermal anomalies in wadi deposits, and adjacent sandy areas. The remote sensing results were validated using comprehensive field observations including, pumping tests, water wells data, and vegetation patterns in the study area. The study concluded that a groundwater possibility map based on geospatial techniques and remote sensing data can provide a robust tool in groundwater exploration, and consequently, it can be adopted elsewhere in arid regions.
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Ponnamma, Deepalekshmi, Kishor Kumar Sadasivuni, Sabu Thomas, Igor Krupa i Mariam Al-Ali AlMa'adeed. "FLEXIBLE OIL SENSORS BASED ON MULTIWALLED CARBON NANOTUBE–FILLED ISOPRENE ELASTOMER COMPOSITES". Rubber Chemistry and Technology 89, nr 2 (1.06.2016): 306–15. http://dx.doi.org/10.5254/rct.15.84841.
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ABSTRACT Oil spills due to either accidents or deliberate oily discharges cause severe pollution and can be thwarted if proper detection facilities are applied. This article reports new flexible oil sensor capabilities of three different elastomer (natural rubber, butyl rubber, and styrene–isoprene–styrene copolymer) composites of multiwalled carbon nanotubes (MWCNTs). We highlight the sensor manufacturing by simple means of solution mixing, and the uniform dispersion of MWCNTs in the elastomers is substantiated with the help of morphology and structural analyses. Electrical percolation and semiconductor characteristics were also examined for composites. The developed materials show better oil sensing above the percolation level, and the filler–polymer interfacial interaction is the main factor regulating the oil-detecting capability. The efficiency of the sensors was also tested after many instances of bending.
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Tonkov, D. N., M. I. Kobylyatskaya, E. S. Vasilyeva, A. V. Semencha i V. E. Gasumyants. "Conductive properties of flexible polymer composites with different carbon-based fillers". Journal of Physics: Conference Series 2227, nr 1 (1.03.2022): 012022. http://dx.doi.org/10.1088/1742-6596/2227/1/012022.
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Abstract This paper is devoted to the comparative study of conductive properties of three types of flexible polymer composites consisting of styrene-butadiene rubber (SBR) as a matrix and graphite, graphene or single-walled carbon nanotubes as fillers. The dependences of the resistivity on the mass fraction of different fillers are measured and analyzed within the framework of the statistical percolation theory. The percolation parameters (the values of the percolation threshold and the critical exponent) are calculated for all studied composites. Their variation depending on the filler type is discussed, taking into account a geometric shape of filler particles and the nature of the conduction process in composites in the percolation range. The sensitivity of the resistivity of synthesized composites to axial deformation at different mass fraction of fillers is also investigated. Using graphite or graphene fillers is observed to result in a higher sensitivity compared to the carbon nanotubes filler. The highest value of the gauge factor is observed when using 23 mass.% graphene filler that indicates graphene/SBR composites to be most promising for creating strain sensors.
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Olivé-Monllau, Rosa, Mireia Baeza, Jordi Bartrolí i Francisco Céspedes. "Novel Amperometric Sensor Based on Rigid Near-Percolation Composite". Electroanalysis 21, nr 8 (kwiecień 2009): 931–38. http://dx.doi.org/10.1002/elan.200804494.
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