Jiri Matyas

Pre-Strain Stimulation of Electro-Mechanical Sensitivity of Carbon Nanotube Network/Polyurethane Composites

The change of electrical resistance of a highly extensible composite sensors consisting of a network of entangled multi-wall carbon nanotubes (CNTs) and thermoplastic polyurethane elastomer in the course of elongation was stimulated by initial tensile deformation. Though the initial deformation irreversibly changes the arrangement of CNT network, subsequent cyclic elongation and corresponding resistance change is stable. The resistance sensitivity, quantified by a gauge factor, which defines the sensitivity of strain sensor as the relative resistance change divided by the applied strain, increases nearly five times from the value of about five for not initially elongated composites. This is a substantial increase, which ranks the composites among materials with the highest electromechanical sensitivity. The observed sensitivity increase is discussed on basis of the cracking of a nanotube network with extension when the number of contacts between nanotubes decreases and thus the network has fewer interconnections that can carry an electric current.

Antenna of silver nanoparticles mounted on a flexible polymer substrate constructed using inkjet print technology

This article describes the construction of an antenna that operates at frequencies of 1.07, 1.5, and 2.49 GHz and that is fabricated on a flexible polymer substrate using inkjet printing technology. In particular, this article is focused on the preparation and characterization of an antenna starting from the ink formulation for printing a homogeneous, electrically conductive layer using silver nanoparticles. The diameter of the prepared silver nanoparticles ranges from 50 to 200 nm. The inkjet printing technology on flexible polymer substrates offers a wide range of applications where there are high demands for flexibility. In combination with the polymer substrate, inkjet printing enables the production of more complex shapes and curves for antennas that are widely applicable not only in wearable electronic devices but also in plastic cases for portable communication devices.

The Multifunctional Composite on the Base of Carbon Nanotubes Network and its Use as a Passive Antenna and Gas Sensing Element

Carbon nanotubes in the form of entangled network can be used as a multifunctional composite material for a wide range of using. A new and perspective usage is a passive antenna and gas sensing element. The antenna works well at 1.284 GHz. The local reflection minimum is 11.48 dB. The reflection coefficient r=0.2667. The transmission power in this frequency is 93%. Multiwall carbon nanotubes (MWCNT) network Buckypaper was made by the vacuum filtration method of MWCNT aqueous suspension. The sensitivity of multi-wall carbon nanotube (MWCNT) networks of randomly entangled pure and HNO3 oxidized nanotubes to polar and nonpolar organic vapors (ethanol, heptane), has been investigated by resistance measurements. The results demonstrate that the network electrical resistance increases when exposed to organic solvent vapors, and a reversible reaction is observed when the sample is removed from the vapors. The investigated MWCNT networks could be potentially used as sensing elements for sensitive and selective organic vapor detection.

Using graphene/styrene-isoprene-styrene copolymer composite thin film as a flexible microstrip antenna for the detection of heptane vapors

BelSU, Belgorod National Research University; LO1504, NPU, Northwestern Polytechnical University; MEYS, Ministry of Education, Youth and Science; CZ.1.05/2.1.00/19.0409, FEDER, European Regional Development Fund; IGA/CPS/2016/002, FEDER, European Regional Development Fund; FEDER, European Regional Development Fund; Research and Development

A built-in sensor with carbon nanotubes coated by Ag clusters for deformation monitoring of glass fibre/epoxy composites

AV0Z20600510; LO1504, NPU, Northwestern Polytechnical University; STINT, Swedish Foundation for International Cooperation in Research and Higher Education; IGA/CPS/2017/002, FEDER, European Regional Development Fund; CZ.1.05/2.1.00/19.0409, FEDER, European Regional Development Fund; BelSU, Belgorod National Research University; -7AMB16AT033, MEYS, Ministry of Education, Youth and Science; Research and Development; FEDER, European Regional Development Fund

Effect of pre-strain and KMnO4 oxidation of carbon nanotubes embedded in polyurethane on strain dependent electrical resistance of the composite

Purpose The synergistic effect of functionalization of multi-walled carbon nanotubes (CNT) using KMnO4 oxidation and initial tensile deformation on the electrical resistance of nanotube network/polyurethane composite subjected to elongation was studied. Design/methodology/approach Though the initial deformation irreversibly changed the arrangement of carbon nanotube network, subsequent cyclic elongation confirmed stable resistance values. The increased strain-dependent resistance of stimulated nanotube network/polyurethane composite was demonstrated by monitoring vibration of tambour leather after a bead impact and finger flexion. Findings The results showed a tenfold composite resistance increase for the composite prepared from KMnO4 oxidized nanotubes, quantified by a so-called gauge factor, from a value of about 20 in comparison to the network prepared from pristine nanotubes. This is a substantial increase, which ranks the stimulated composite among materials with the highest electromechanical response. Originality/value The results in this paper are new and have not been published yet. The paper combines different ideas which are developed together. It presents a new concept of synergistic effect of CNT oxidation and application of pre-strain simulation. Oxidation and pre-strain increases by several times the sensitivity of the tested composites which are predetermined for use as strain sensors of various sizes and shapes.

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%.

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.

Sensing element for detection of polar organic vapours on the base of polyaniline-composite - Effect of substrate surface area

Conductive polymer polyaniline (PANI) was synthesized by oxidative polymerization of aniline hydrochloride as a source of aniline and ammonium persulfate as an oxidation agent. The polymerization process is relatively easy and cheap. The reaction was carried out in presence of polymer substrate, in our case polyethylene terephthalate (PET) as a representative of smooth surface substrate and polyvinylidenfluoride (PVDF) nanofibers membrane as a representative of porous substrate. Both these substrates were covered by polyaniline (PANI) and used as a sensing element for organic vapors detection. The detection was made by measuring and the record of the change of resistivity during adsorption and desorption of saturated vapors. The result shows that sensitivity decreases with increasing polarity of chosen solvent in order N,N- Dimethylformamide (DMF), N,N-Dimethylacetamide (DMAc) and Dimethyl sulfoxide (DMSO). The PANI base sensing element on PVDF substrate improves sensitivity, selectivity and it also has good reversibility and repeatability.