Printed Graphene, Nanotubes and Silver Electrodes Comparison for Textile and Structural Electronics Applications

Sensors 2021, 21(12), 4038

Figure 9. Scanning Electron Microscopy micrograph image presenting the morphology of the sample surface with printed graphene paste containing 10 wt.% GNP in PMMA organic vehicle.

Due to the appearance of smart textiles and wearable electronics, the need for electro-conductive textiles and electro-conductive paths on textiles has become clear. In this article the results of a test of developed textile electro-conductive paths obtained by applying the method of screen printing pastes containing silver nanoparticles and carbon (graphene, nanotubes, graphite) are presented. Conducted research included analysis of the adhesion test, as well as evaluation of the surface resistance before and after the washing and bending cycles. Obtained results indicated that the samples with the content of carbon nanotubes 3% by weight in PMMA on substrate made of aramid fibers (surface mass of 260 g/m2) were characterized by the best adhesion and the best resistance to washing and bending cycles. Such electro-conductive paths have potential to be used in smart clothing applications.

Carbon Nanotube-Based Composite Filaments for 3D Printing of Structural and Conductive Elements

Applied Sciences 2021, 11(3), 1272S

 

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.

Additive manufacturing of electronics from silver nanopowders sintered on 3D printed low-temperature substrates

… wkrótce w Advanced Engineering Materials.

Additive manufacturing is more widely used these days in aerospace, power industry, and automotive. The latest reports indicate that electronics can be produced with this technique. This approach requires the development of new materials for the fabrication of conductive metallic layers on polymers. Herein, a hybrid technique based on fused deposition modeling, direct‐write, and selective laser sintering is demonstrated, for the fabrication of structural electronics. Highly conductive paths are obtained with conductivity values up to 3.2·106 S m−1 in a single printing and sintering additive process. The influence of process parameters is evaluated with several 3D printed polymer substrates affecting the electrical conductivity of the printed conductive paths and circuits. The developed hybrid technique allows performing selective thermal sintering of metallic pastes on polymer substrates exhibiting the value of melting temperatures much lower than the sintering temperature of the silver paste. This phenomenon can be explained with the proposed hypothesis that the activation energy of the sintering process of metallic paste and degradation of polymer substrate plays a key role in obtaining functional conductive metallic paths on polymer substrates. Application of the developed process is demonstrated with a simple human interface device and a circuit with light‐emitting diodes and power source.

Carbon Nanotube Embedded Adhesives for Real-time Monitoring of Adhesion Failure in High Performance Adhesively Bonded Joints

Scientific Reports 10, 16833 (2020)

Carbon nanotubes (CNTs) embedded polymers are of increasing interest to scientific and industrial communities for multi-functional applications. In this article, CNTs have been introduced to high-strength epoxy adhesive for enabling in-situ strain sensing in adhesively bonded aluminium-to-aluminium single-lap joints to accurately indicate the onset and propagation of adhesion failure to the evolution of piezo-resistivity in varying mechanical loads. The CNT modified adhesive in bonded joints and the CNT modified adhesive alone have been tested under monothonic and cyclic tensile loads up to ultimate failure. The changes in the piezo-resistivity induced by the CNTs have been monitored in situ with respect to loading. A novel interpretation method has been developed for progressive, instantaneous adhesion failure estimation under cyclic tensile stresses from a resistivity baseline. The method indicates that the in-situ resistivity changes and the rate of the changes with strain, i.e. sensitivity, strongly correlate with the adhesion failure progression, irrespective of the CNT dispersion quality. Moreover, the effect of bond thickness on the evolution of piezo-resistivity and adhesion failure have been studied. It was observed that relatively thin adhesive bonds (0.18 mm thickness), possessing higher CNT contact points than thick bonds (0.43 mm thickness), provide 100 times higher sensitivity to varying cyclic loads.

Koniec!

… choć to jeszcze nie zakończenie.

„Wykonywanie czegoś co się wymyśliło jest bardzo nudne. W społeczeństwie tkwi przymus kończenia prac. To zdaniem ogółu jest stosowne. Sprzeciwiałem się wszystkiemu co stosowne.” – Marcel Duchamp

Flexible Gas Sensor Printed on a Polymer Substrate for sub-ppm Acetone Detection

Electronic Materials Letters (2020).

Graphical abstract

Gas sensors are widely used in many industrial and home applications. There is therefore continued need to develop novel gas sensor substrates which provide good mechanical and electrical stability, and good flexibility in comparison with the conventional alumina and silicon-based materials. In this paper, we present the experimental results on flexible gas sensors based on the Kapton foil and alumina substrate covered by copper oxide as a gas-sensitive layer. These sensors exhibited good mechanical stability and gas-sensing characteristics. The Kapton-based CuO gas sensors were tested under exposure to acetone in the 0.05–1.25 ppm range (150 °C, 50%RH). The results confirmed that sensors deposited on the flexible substrate such as Kapton can be used in the exhaled breath analyzers dedicated to diabetes biomarker detection or other applications for which the elastic substrate is needed.

Zaczynajmy przygodę z ERC.

Nadeszła wiekopomna chwila, w której po miesiącach przygotowywań, zmiany celu życiowego, ustawiania priorytetu/ów i wytrwałej walki o słuszne idee i wartości, złożyłem wniosek do konkursu ERC Consolidator Grant. Cieszę się, że Fundacja promuje takie inicjatywy, więc pozostaje trzymać kciuki za pomyślne rozpatrzenie wniosku o przedłużenie czasu realizacji projektu First Team.

Highly Conductive Carbon Nanotube-Thermoplastic Polyurethane Nanocomposite for Smart Clothing Applications and Beyond

Nanomaterials 2019, 9(9), 1287

The following paper presents a simple, inexpensive and scalable method of production of carbon nanotube-polyurethane elastomer composite. The new method enables the formation of fibers with 40% w/w of nanotubes in a polymer. Thanks to the 8 times higher content of nanotubes than previously reported for such composites, over an order of magnitude higher electrical conductivity is also observed. The composite fibers are highly elastic and both their electrical and mechanical properties may be easily controlled by changing the nanotubes content in the composite. It is shown that these composite fibers may be easily integrated with traditional textiles by sewing or ironing. However, taking into account their light-weight, high conductivity, flexibility and easiness of molding it may be expected that their potential applications are not limited to the smart textiles industry.

Electrical and rheological percolation threshold of graphene pastes for screen-printing

Circuit World, vol. 45, no. 1, pp. 26–30, 2019

A comparison of electric and viscosity percolation threshold is crucial from the scientific and technical points of view to understand the features and capabilities of heterogeneous graphene composite materials and properly select the functional phase volume. Therefore, the purpose of this paper is to present the analysis of the electrical and rheological percolation thresholds in the polymer–graphene screen printing pastes and the analysis of the relation between these two parameters.

In the paper, the properties of polymer-based pastes with graphene nanoplatelets were tested: paste viscosity and printed layers conductivity. The tests of pastes with different filler content allowed to determine both the electrical and rheological percolation thresholds using power law, according to Kirkpatrick’s percolation model.

The electrical percolation threshold for graphene nanoplatelets (GNPs) in the composite was 0.74 Vol.% when the rheological percolation threshold is observed to be at 1.00 Vol.% of nanoplatelets. The percolation threshold values calculated using the Kirkpatrick’s percolation model were 0.87 and 0.5 Vol.% of GNPs in the paste for electrical and rheological percolation thresholds, respectively.

Recently, GNPs are becoming more popular as the material of the functional phase in screen printing heterophase materials, because of their unique mechanical and electrical properties. However, till date no research presented in the literature is related to the direct comparison of both the electrical and rheological percolation thresholds. Such analysis is important for the optimization of the printing process toward the highest quality of printed conductive paths, and finally the best electrical properties.

Photonic curing of silver paths on 3D printed polymer substrate

Circuit World, Vol. 45 Issue: 1, pp.26-30, 2019

Despite almost limitless possibilities of rapid prototyping, the idea of 3D printed fully functional electronic device still has not been fulfilled – the missing point is a highly conductive material suitable for this technique. The purpose of this paper is to present the usage of the photonic curing process for sintering highly conductive paths printed on the polymer substrate.

This paper evaluates two photonic curing processes for the conductive network formulation during the additive manufacturing process. Along with the xenon flash sintering for aerosol jet-printed paths, this paper examines rapid infrared sintering for thick-film and direct write techniques.

This paper proves that the combination of fused deposition modeling, aerosol jet printing or paste deposition, along with photonic sintering, is suitable to obtain elements with low resistivity of 3,75·10−8 Ωm. Presented outcomes suggest the solution for fabrication of the structural electronics systems for daily-use applications.

The combination of fused deposition modelling (FDM) and aerosol jet printing or paste deposition used with photonic sintering process can fill the missing point for highly conductive materials for structural electronics.