A Review of Multiple Scale Fibrous and Composite Systems for Heating Applications

Spinning the Future: The Convergence of Nanofiber Technologies and Yarn Fabrication

The rapid advancement in nanofiber technologies has revolutionized the domain of yarn materials, marking a significant leap in textile technology. This review dissects the nexus between cutting-edge nanofiber technologies and yarn manufacturing, aiming to illuminate the pathway toward engineering advanced textiles with unparalleled functionality. It first discusses the fundamentals of nanofiber assemblies and spinning techniques, primarily focusing on electrospinning, centrifugal spinning, and blow spinning. Additionally, the study delves into integrating nanofiber spinning technologies with traditional and modern yarn fabrication principles, elucidating the design principles that underlie the creation of yarns incorporating nanofibers. Twisting technologies are explored to examine how they can be optimized and adapted for incorporating nanofibers, thus enabling the production of innovative nanofiber-based yarns. Special attention is given to scalable strategies like centrifugal and blow spinning, which are spotlighted for their efficiency and scalability in fabricating nanofiber yarns. This review further analyses recently developed nanofiber yarn applications, including wearable sensors, biomedical devices, moisture management textiles, and energy harvesting and storage devices. We finally present a forward-looking perspective to address unresolved issues in nanofiber-based yarn technologies.

High-Performance, Easy-to-Fabricate, Nanocomposite Heater for Life Sciences and Biomedical Applications

Microheaters are used in several applications, including medical diagnostics, synthesis, environmental monitoring, and actuation. Conventional microheaters rely on thin-film electrodes microfabricated in a clean-room environment. However, low-cost alternatives based on conductive paste electrodes fabricated using printing techniques have started to emerge over the years. Here, we report a surprising effect that leads to significant electrode performance improvement as confirmed by the thorough characterization of bulk, processed, and conditioned samples. Mixing silver ink and PVA results in the solubilization of performance-hindering organic compounds. These compounds evaporate during heating cycles. The new electrodes, which reach a temperature of 80 °C within 5 min using a current of 7.0 A, display an overall 42% and 35% improvement in the mechanical (hardness) and electrical (resistivity) properties compared to pristine silver ink electrodes. To validate our results, we use the composite heater to amplify and detect parasite DNA from Trypanosoma brucei, associated with African sleeping sickness. Our LAMP test compares well with commercially available systems, confirming the excellent performance of our nanocomposite heaters. Since their fabrication relies on well-established techniques, we anticipate they will find use in a range of applications.

Multiscale Carbon Fibre-Carbon Nanotube Composites of Poly(Vinyl Chloride)-An Evaluation of Their Properties and Structure

To date, there has been limited information in the literature on the application of carbon fibre-carbon nanotube systems for the modification of poly(vinyl chloride) (PVC) matrixes by micro- and nanometric fillers and an evaluation of the properties of the unique materials produced. This paper presents the results of newly designed unique multiscale composites. The advantages of the simultaneous use of carbon fibres (CFs) and carbon nanotubes (CNTs) in PVC modification are discussed. To increase the dispersibility of the nanofiller, CFs together with nanotubes were subjected to a sonication process. The resulting material was introduced into PVC blends, which were processed by extrusion. The ratio of components in the hybrid filler with CF_CNT was 20:1, and its proportion in the PVC matrix was 1, 5, and 10 wt.%, respectively. Comparatively, PVC composites modified only with carbon fibres were obtained. The structure, thermal, electrical, and mechanical properties and swelling resistance of the composites were studied. The study showed a favourable homogeneous dispersion of nanotubes in the PVC matrix. This enabled effective modification of the structure at the nanometric level and the formation of an interpenetrating network of well-dispersed hybrid filler, as evidenced by a decrease in volume resistivity and improvement in swelling resistance, as well as an increase in glass transition temperature in the case of PVC/CF_CNT composites.

Independent Heating Performances in the Sub-Zero Environment of MWCNT/PDMS Composite with Low Electron-Tunneling Energy

The structural stability of various structures (railroads, bridges, buildings, etc.) is lowered due to freezing because of the decreasing outside temperature in winter. To prevent damage from freezing, a technology for de-icing has been developed using an electric-heating composite. For this purpose, a highly electrically conductive composite film with multi-wall carbon nanotubes (MWCNTs) uniformly dispersed in a polydimethylsiloxane (PDMS) matrix through a three-roll process was fabricated by shearing the MWCNT/PDMS paste, through a two-roll process. The electrical conductivity and the activation energy of the composite were 326.5 S/m and 8.0 meV at 5.82 Vol% of MWCNTs, respectively. The dependence of the electric-heating performance (heating rate and temperature change) on the applied voltage and environmental temperature (from -20 °C to 20 °C) was evaluated. The heating rate and effective-heat-transfer characteristics were observed to decrease as the applied voltage increased, while they showed the opposite tendency when the environmental temperature was at sub-zero temperatures. Nevertheless, the overall heating performance (heating rate and temperature change) was maintained with little significant difference in the considered external-temperature range. The unique heating behaviors can result from the low activation energy and the negative-temperature (T) coefficient of resistance (R) (NTCR, dR/dT < 0) of the MWCNT/PDMS composite.

Enhancement of Electromagnetic Wave Shielding Effectiveness by the Incorporation of Carbon Nanofibers-Carbon Microcoils Hybrid into Commercial Carbon Paste for Heating Films

Carbon microcoils (CMCs) were formed on stainless steel substrates using C₂H₂ + SF₆ gas flows in a thermal chemical vapor deposition (CVD) system. The manipulation of the SF₆ gas flow rate and the SF₆ gas flow injection time was carried out to obtain controllable CMC geometries. The change in CMC geometry, especially CMC diameter as a function of SF₆ gas flow injection time, was remarkable. In addition, the incorporation of H₂ gas into the C₂H₂ + SF₆ gas flow system with cyclic SF₆ gas flow caused the formation of the hybrid of carbon nanofibers-carbon microcoils (CNFs-CMCs). The hybrid of CNFs-CMCs was composed of numerous small-sized CNFs, which formed on the CMCs surfaces. The electromagnetic wave shielding effectiveness (SE) of the heating film, made by the hybrids of CNFs-CMCs incorporated carbon paste film, was investigated across operating frequencies in the 1.5-40 GHz range. It was compared to heating films made from commercial carbon paste or the controllable CMCs incorporated carbon paste. Although the electrical conductivity of the native commercial carbon paste was lowered by both the incorporation of the CMCs and the hybrids of CNFs-CMCs, the total SE values of the manufactured heating film increased following the incorporation of these materials. Considering the thickness of the heating film, the presently measured values rank highly among the previously reported total SE values. This dramatic improvement in the total SE values was mainly ascribed to the intrinsic characteristics of CMC and/or the hybrid of CNFs-CMCs contributing to the absorption shielding route of electromagnetic waves.

Joule-Heating Effect of Thin Films with Carbon-Based Nanomaterials

Smart textiles have become a promising area of research for heating applications. Coatings with nanomaterials allow the introduction of different functionalities, enabling doped textiles to be used in sensing and heating applications. These coatings were made on a piece of woven cotton fabric through screen printing, with a different number of layers. To prepare the paste, nanomaterials such as graphene nanoplatelets (GNPs) and multiwall carbon nanotubes (CNTs) were added to a polyurethane-based polymeric resin, in various concentrations. The electrical conductivity of the obtained samples was measured and the heat-dissipating capabilities assessed. The results showed that coatings have induced electrical conductivity and heating capabilities. The highest electrical conductivity of (9.39 ± 1.28 × 10⁻¹ S/m) and (9.02 ± 6.62 × 10⁻² S/m) was observed for 12% (w/v) GNPs and 5% (w/v) (CNTs + GNPs), respectively. The sample with 5% (w/v) (CNTs + GNPs) and 12% (w/v) GNPs exhibited a Joule effect when a voltage of 12 V was applied for 5 min, and a maximum temperature of 42.7 °C and 40.4 °C were achieved, respectively. It can be concluded that higher concentrations of GNPs can be replaced by adding CNTs, still achieving nearly the same performance. These coated textiles can potentially find applications in the area of heating, sensing, and biomedical applications.

Effect of GNPs on the Piezoresistive, Electrical and Mechanical Properties of PHA and PLA Films

Sustainability has become the primary focus for researchers lately. Biopolymers such as polyhydroxyalkanoate (PHA) and polylactic acid (PLA) are biocompatible and biodegradable. Introducing piezoresistive response in the films produced by PLA and PHA by adding nanoparticles can be interesting. Hence, a study was performed to evaluate the mechanical, electrical and piezoresistive response of films made from PHA and PLA. The films were produced by solvent casting, and they were reinforced with graphene nanoplatelets (GNPs) at different nanoparticle concentrations (from 0.15 to 15 wt.%). Moreover, cellulose nanocrystals (CNC) as reinforcing elements and polyethylene glycol (PEG) as plasticizers were added. After the assessment of the nanoparticle distribution, the films were subjected to tests such as tensile, electrical conductivity and piezoresistive response. The dispersion was found to be good in PLA films and there exist some agglomerations in PHA films. The results suggested that the incorporation of GNPs enhanced the mechanical properties until 0.75 wt.% and they reduced thereon. The addition of 1% CNCs and 20% PEG in 15 wt.% GNPs’ tensile values deteriorated further. The PHA films showed better electrical conductivity compared to the PLA films for the same GNPs wt.%. Gauge factor (GF) values of 6.30 and 4.31 were obtained for PHA and PLA, respectively.