Accelerated shape forming and recovering, induction, and release of adhesiveness of conductive carbon nanotube/epoxy composites by joule heating

The versatile properties of a nanopaper consisting of a porous network of multi-walled carbon nanotubes were applied to enhance the mechanical and electrical properties of a thermosetting epoxy polymer. The embedded nanopaper proved useful both in the monitoring of the curing process of the epoxy resin by the self-regulating Joule heating and in the supervising of tensile deformations of the composite by detecting changes in its electrical resistance. When heated by Joule heating above its glass transition temperature, the embedded carbon nanotube nanopaper accelerated not only the modelling of the composites into various shapes, but also the shape recovery process, wherein the stress in the nanopaper was released and the shape of the composite reverted to its original configuration. Lastly, in comparison with its respective epoxy adhesive, the internally heated electro-conductive carbon nanotube nanopaper/epoxy composite not only substantially shortened curing time while retaining comparable strength of the adhesive bonding of the steel surfaces, but also enabled a release of such bonds by repeated application of DC current. © 2020 by the authors.Ministry of Education, Youth and Sports of the Czech Republic-Program NPU I [LO1504]; Operational Program Research and Development for Innovations - European Regional Development FundEuropean Union (EU); national budget of the Czech Republic [CZ.1.05/2.1.00/19.0409]; Fund of the Institute of Hydrodynamics [AV0Z20600510

The piezoresistive highly elastic sensor based on carbon nanotubes for the detection of breath

Wearable electronic sensor was prepared on a light and flexible substrate. The breathing sensor has a broad assumption and great potential for portable devices in wearable technology. In the present work, the application of a flexible thermoplastic polyurethane/multiwalled carbon nanotubes (TPU/MWCNTs) strain sensor was demonstrated. This composite was prepared by a novel technique using a thermoplastic filtering membrane based on electrospinning technology. Aqueous dispersion of MWCNTs was filtered through membrane, dried and then welded directly on a T-shirt and encapsulated by a thin silicone layer. The sensing layer was also equipped by electrodes. A polymer composite sensor is capable of detecting a deformation by changing its electrical resistance. A T-shirt was capable of analyzing a type, frequency and intensity of human breathing. The sensitivity to the applied strain of the sensor was improved by the oxidation of MWCNTs by potassium permanganate (KMnO4) and also by subsequent application of the prestrain.Ministry of Education, Youth and Sports of the Czech Republic-Program NPU I [LO1504]; Operational Program Research and Development for Innovations; TBU in Zlin [IGA/CPS/2018/005, IGA/CPS/2019/010]; national budget of the Czech Republic, within project CPS-strengthening research capacity [CZ.1.05/2.1.00/19.0409]; European Regional Development Fund (ERDF)European Union (EU

High sensitivity sensor development for Hexamethylphosphoramide by polyaniline coated polyurethane membrane using resistivity assessment technique

Hexamethylphosphoramide is considered as one of the harmful of all carcinogens. In the present work, detection of Hexamethylphosphoramide by using a polyaniline coated polyurethane membrane was carried out and device is constructed to show its practical application using resistivity assessment technique. Polyurethane nanofiber membrane was prepared by electrospinning process. A modified synthetic method used to coat polyaniline onto a polyurethane membrane found to be effective to prepare a uniform and electrically conductive coating and promising for sensing a carcinogen like Hexamethylphosphoramide. Sensing performance may be attributed to the large resistance change in polyaniline because of the deprotonation when exposed to the Hexamethylphosphoramide environment. However, it is interesting to know that the high sensitivity of polyaniline modified polyurethane membrane toward Hexamethylphosphoramide is used as a promising gas sensor for the detection of said carcinogen using resistivity assessment technique at room temperature. © 2016 Elsevier Ltd. All rights reserved.LO1504, MEYS, Ministry of Education, Youth and SportsMinistry of Education, Youth and Sports of the Czech Republic - Program NPU I [LO1504

Microstrip antenna from silver nanoparticles printed on a flexible polymer substrate

This work describes the use of inkjet printing technology to fabricate a flexible microstrip antenna. The antenna is printed on a flexible PET foil (Polyethylene terephthalate) using silver nanoparticles. Silver nanoparticles were synthetized by the solvothermal precipitation technique. The diameter of the prepared silver nanoparticles ranges from 20 to 200 nm measured with the help of the SEM analysis. In addition, the ink formulation for printing of a homogenous and electrically conductive layer was further prepared using silver nanoparticles. The printed antenna operates in two frequency bands of 2.02 GHz (-16.02 db) and 2.3 GHz (-19.33 db). The antenna is flexible and weigh is only 0.208 g and is suitable for electronic devices of a very low weight, such as wearable electronic devices. © 2017 Elsevier Ltd.Ministry of Education, Youth and Sports of the Czech Republic - National Sustainability Program NPU I [LO1504]; Operational Program Research and Development for Innovations; European Regional Development Fund (ERDF); national budget of the Czech Republic [CZ.1.05/2.1.00/19.0409

Flexible microstrip antenna based on carbon nanotubes/(ethylene-octene copolymer) thin composite layer deposited on PET substrate

A most of portable devices, such as mobile phones, tablets, uses antennas made of cupper. In this paper we demonstrate possible use of electrically conductive polymer composite material for such antenna application. Here we describe the method of preparation and properties of the carbon nanotubes (CNTs)/(ethylene-octene copolymer) as flexible microstrip antenna. Carbon nanotubes dispersion in (ethylene-octene copolymer) toluene solution was prepared by ultrasound finally coating PET substrate by method of dip-coating. Main advantages of PET substrate are low weight and also flexibility. The final size of flexible microstrip antenna was 5 x 50 mm with thickness of 0.48 mm (PET substrate 0.25 mm) with the weight of only 0.402 g. Antenna operates at three frequencies 1.66 GHz (-6.51 dB), 2.3 GHz (-13 dB) and 2.98 GHz (-33.59 dB). © Published under licence by IOP Publishing Ltd

The sensing properties of carbon nanotube filled copolymers for VOC vapors detection

Nowadays, carbon nanotubes are a widely available material, especially multiwall carbon nanotubes. In addition to many other applications, they find use in all kinds of sensors, like deformation, motion, tensile and pressure responsive elements. Numerous applications in sensors for volatile organic compounds (VOCs) are reported as well, nevertheless, they mainly suffer from low selectivity. Therefore, in this research, a sensor containing MWCNTs dispersed in a functional polymer matrix was prepared. As a polymer matrix, styreneisoprene- styrene elastomer was chosen. The standard sensing mechanism of entangled MWCNTs is based on the quality of the contacts (charge transfer) between the individual nanotubes. In the prepared nanocomposite, the mechanism is modified due to the presence of the otherwise non-conductive matrix. The changes of conductivity depend on the response of the percolating nanotube filler network to the swelling of the polymer matrix due to adsorption of VOCs. The tested gas substances have high values of diffusion coefficient for the polymer, so they have a quick response. Then, the selectivity is ensured by differences in solubility of the tested VOCs in the polymer. The effect was demonstrated for four VOCs differing by their affinity to the polymer matrix, namely, heptane, toluene, acetone, and ethanol. © 2021 TANGER Ltd., Ostrava.Internal Grant Agency of the Tomas Bata University in Zlin [IGA/CPS/2019/007]; project CPS-strengthening research capacity [CZ.1.05/2.1.00/19.0409]; Ministry of Education, Youth and Sports of the Czech Republic -DKRVO [RP/CPS/2020/006]RP/CPS/2020/006; Ministerstvo Školství, Mládeže a Tělovýchovy, MŠMT; Univerzita Tomáše Bati ve Zlíně: CZ.1.05/2.1.00/19.0409, IGA/CPS/2019/00

Electro-mechanical transducer based on carbon nanotube network / polystyrene laminate for deformation detection

A new type of polystyrene (PS)/carbon nanotube (CNT) network laminate is introduced as an electrically conductive composite material; with favorable properties as electro-mechanical signal transducer capable to detect applied mechanical strain. In course of its fabrication a non-woven polystyrene membrane made by electro spinning was used as filtering mesh for CNT aqueous dispersion. Produced semi-product like filtering membrane with entrapped carbon nanotubes was stuck using solvent of PS on polystyrene test specimen. The electrical resistance of final laminate is sensitive to tensile strain when elongation leads to increase of macroscopic electrical resistance. Test specimens were then tested in the course of monotonic strain growth and also when loading/unloading cycles were imposed. Changes in resistance were found to be reversible, reproducible and deformation can by monitored in real time. Finally, sensitivity to strain can be quantified by means of a gauge factor, GF, which defines sensitivity of strain gauge as a relative resistance change divided by the applied strain. Measured GF for PS/CNT laminates reaches relatively high values, compared with ones of commonly used metallic strain gauges, serving for values of around 13 and applied tensile deformation in range 0.1-0.6 %. These experimental results are really promising serving for real practical application of this principle in course of polymeric based strain gauges or as an integrated PS/CNT units into polystyrene based constructions for their so called "health monitoring"

Strengthening mechanism of electrothermal actuation in the epoxy composite with an embedded carbon nanotube nanopaper

We assessed an effect of an embedded electro-conductive multiwalled carbon nanotube nanopaper in an epoxy matrix on the release of the frozen actuation force and the actuation torque in the carbon nanotube nanopaper/epoxy composite after heating above its glass transition temperature. The presence of the nanopaper augmented the recovery of the actuation stress by the factor of two in comparison with the pure epoxy strips. We proposed a procedure that allowed us to assess this composite strengthening mechanism. The strengthening of the composite was attributed to the interlocking of the carbon nanotubes with the epoxy. When reheated, the composite samples, which contained stretched mutually intertwined nanotubes and epoxy segments, released a greater actuation stress then the epoxy samples, which comprised of less elastic networks of crosslinked segments of pure epoxy. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.Ministry of Education, Youth and Sports of the Czech Republic-DKRVO [RP/CPS/2020/006]; National Budget of the Czech Republic: the project CPSV-Strengthening Research Capacity [CZ.1.05/2.1.00/19.0409]; Czech Academy of Sciences, Czech Republic [RVO: 67985874]RP/CPS/2020/006; 67985874, CZ.1.05/2.1.00/19.0409; Ministerstvo Školství, Mládeže a Tělovýchovy, MŠMT; Akademie Věd České Republiky, AV Č

High elastic polyurethane/carbon nanotube composite laminate for structure health monitoring by gain shifting of antenna sensing element

The composite of carbon nanotubes and polyurethane (PU) was prepared by simple filtration technique. The PU nonwoven filtration membrane was prepared by electrospinning. A layer of carbon nanotubes was prepared by vacuum filtration on the surface of PU membrane. The resulting composite was subsequently placed on highly elastic polyurethane substrate. The contribution shows an efficient method of preparing the sensing element for monitoring the state of strain of loaded structures by using highly elastic polyurethane / carbon nanotubes composite. This sensor has been involved as passive antenna with stable resonance frequency of 650 MHz. When it is get deformed in the range from 0 to 3.5% the sensor gain was changing from -39 dB to - 19.45 dB. But if it is get deformed by 15% and again measured strain from 0 to 3.5%, sensor gain was changing from -33 dB to -12.3 dB, which clearly indicates the damage of structure. © Published under licence by IOP Publishing Ltd

Improving sensitivity of the polyurethane/CNT laminate strain sensor by controlled mechanical preload

This article describes strain detection potential of polyurethane/CNT layered composite and further possible enhance of its sensitivity to strain, expressed by value of gauge factor, GF, employing its controlled mechanical preload. In course of its fabrication a non-woven polyurethane membrane made by electro spinning was used as filtering membrane for CNT aqueous dispersion. Final CNT polyurethane laminate composite is prepared by compression molding. Produced polyurethane/CNT composite laminate is electrically conductive and high elastic. Its elongation leads to change of its macroscopic electrical resistance. Changes in resistance are further reversible, reproducible and can monitor deformation in real time. Gauge factor reaches very high values around 8 for strain reaching 3.5% comparing with conventional metallic strain gauges. Finally, controlled mechanical preload significantly increases value of GF. For example for value of 8.1% of preload value of GF reaches 23.3 for strain 3.5%. © Published under licence by IOP Publishing Ltd