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

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

Ethylene-octene-copolymer with embedded carbon and organic conductive nanostructures for thermoelectric applications

Hybrid thermoelectric composites consisting of organic ethylene-octene-copolymer matrices (EOC) and embedded inorganic pristine and functionalized multiwalled carbon nanotubes, carbon nanofibers or organic polyaniline and polypyrrole particles were used to form conductive nanostructures with thermoelectric properties, which at the same time had sufficient strength, elasticity, and stability. Oxygen doping of carbon nanotubes increased the concentration of carboxyl and C-O functional groups on the nanotube surfaces and enhanced the thermoelectric power of the respective composites by up to 150%. A thermocouple assembled from EOC composites generated electric current by heat supplied with a mere short touch of the finger. A practical application of this thermocouple was provided by a self-powered vapor sensor, for operation of which an electric current in the range of microvolts sufficed, and was readily induced by (waste) heat. The heat-induced energy ensured the functioning of this novel sensor device, which converted chemical signals elicited by the presence of heptane vapors to the electrical domain through the resistance changes of the comprising EOC composites. © 2020 by the authors.Operational Program Research and Development for Innovations - European Regional Development Fund (ERDF)European Union (EU); Operational Program Education for Competitiveness - European Social Fund (ESF); National Budget of the Czech Republic [CZ.1.05/2.1.00/03.0111, CZ.1.07/2.3.00/20.0104]; Fund of Institute of Hydrodynamics [AV0Z20600510

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

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

Deformation theory of an electro-conductive composite composed of entangled network of carbon nanotubes embedded in elastic polyurethane

A strain sensing polymer composite consisting of a network of entangled multi-walled carbon nanotubes in a thermoplastic polyurethane elastomer is tested by tensile and bending deformation. The composite is prepared by taking a non-woven polyurethane filter membrane, enmeshing it with carbon nanotubes and melding them together. The testing has shown that the material can be elongated as much as 400% during which the electrical resistance is increased more than 270 times. To describe the composite strain dependent resistance, a rheological model is proposed which takes into account a decrease of local contact forces between nanotubes as well as the reduction of number of contacts with deformation. The theory is used for description of sensing element deformation and resistance when simple elongation and repeated bending is exerted

Microstrip resonant sensor for differentiation of components in vapor mixtures

A novel microstrip resonant vapor sensor made from a conductive multiwalled carbon nanotubes/ethylene-octene copolymer composite, of which its sensing properties were distinctively altered by vapor polarity, was developed for the detection of organic vapors. The alteration resulted from the modified composite electronic impedance due to the penetration of the vapors into the copolymer matrix, which subsequently swelled, increased the distances between the carbon nanotubes, and disrupted the conducting paths. This in turn modified the reflection coefficient frequency spectra. Since both the spectra and magnitudes of the reflection coefficients at the resonant frequencies of tested vapors were distinct, a combination of these parameters was used to identify the occurrence of a particular vapor or to differentiate components of vapor mixtures. Thus, one multivariate MWCNT/copolymer microstrip resonant sensor superseded an array of selective sensors. © 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; CZ.1.05/2.1.00/19.0409; Akademie Věd České Republiky, AV Č

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

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