Influence of Sweat on Joint and Sensor Reliability of E-Textiles

This article addresses reliability under the sweat of interconnection techniques for the mounting surface mounted device (SMD) components and fully printed humidity sensors onto conductive stretchable textile ribbons. Samples underwent testing for the effect of ageing by artificial sweat on their electrical resistance using both alkaline and acidic artificial sweat. The best results in terms of electrical resistance change were obtained for samples soldered to the conductive fibers interwoven in the ribbon. However, this method can damage the ribbon due to the high temperature during soldering and significantly reduce the mechanical properties and flexibility of the ribbon, which can lead to a limited service life of samples. On the other hand, adhesive bonding is a very interesting alternative, where the above-mentioned properties are preserved, but there is a significant effect of sweat ageing on electrical resistance. The results of fully printed graphene-based humidity sensors show that, for the intended use of these sensors (i.e., detection of changes in moisture on the human body), usage of the samples is possible, and the samples are sufficiently reliable in the case of sweat degradation. In addition, the response of the sensor to humidity is quite high: 98% at a relative humidity of 98%.

Measurement of microwave radiation pressure on thin metal fibers

The pressure of electromagnetic radiation in the optical range is widely used to hold microparticles in a given place and control their movement. This is possible by focusing the laser radiation into an area with the dimension of several micrometers. The intensity of radiation in this area is large and sufficient to retain micro-particles in the laser beam and manipulate them. Nowadays, intensive research is underway on the use of microwave and terahertz radiation and the possibility of applying radiation pressure in these ranges. But in the microwave range, the focal spot dimension is much larger than in the optical one. Therefore, control of the objects whose dimensions are comparable to those of the focal spot using the radiation pressure requires very high power. For the objects with small dimensions, a small amount of radiation energy falls on them, and the acting force decreases. However, it is known that thin conductive fibers interact very strongly with microwave radiation. This can be used to levitate short thin metal fibers (vibrators), hold them in predicted place and control their position in space. The paper describes the measurements of the pressure of microwave radiation with a wavelength of 8 mm on thin copper fibers. Torsional balance is used for this purpose. In the metal case on a suspension from a tungsten fiber with a diameter of 8 microns there is located the rocker arm with 50 mm length with receiving elements in the form of system of copper fibers with a diameter of 300 microns and 15 mm length. Microwave radiation was directed to one of the receiving elements using a horn. The calibration of torsion balance, the measurement process, and the evaluation of the resulting error are described. The measurements gave the value of the efficiency factor of the radiation pressure Qpr = 4.86. This agrees satisfactorily with the results of calculations Qpr = 5.39. The difference is 10%.

A Review of Asphaltic Crack Healing Approaches and Its Mechanism

The concept of self-healing has an excellent potential to extend the life of asphalt pavement. This technology can be considered a sustainable technology due to its ability to reduce the utilization of asphalt mixture production materials used for road maintenance, polluting the environment. It is a complex physicochemical process wherein the molecular diffusion healing mechanisms in asphalt materials are inspired by self-healing polymeric systems, which describe the self-recovery behaviors based on polymer chain dynamics. Several methods have been adopted to improve the self-healing of asphalt, one of which is induction healing. It is the process of heating the asphalt pavement incorporated with an electrically conductive material such as steel fibers, wherein asphalt healing is undertaken via electric field induction. Induction healing via induction heating occurs with eddy current where the electric current flows within the conductive fibers when magnetically susceptible under the magnetic field. Microwave heating is another self-healing method similar to induction in which magnetic radiation is employed to treat asphalt mixtures instead of the electric field-induced induction healing processes. The conductive fibers can absorb the electromagnetic (EM) waves to convert them into heat energy through doublet polarization, interface polarization, and electrical conduction dissipation when placed in the microwave field. These two types of heating systems, which are induction heating and microwave heating, are compared and discussed thoroughly in this study. Finally, some recommendations for the future development of self-healing asphalt are proposed.

Development of an Elastic, Electrically Conductive Coating for TPU Filaments

Electrically conductive filaments are used in a wide variety of applications, for example, in smart textiles and soft robotics. Filaments that conduct electricity are required for the transmission of energy and information, but up until now, most electrically conductive fibers, filaments and wires offer low mechanical elongation. Therefore, they are not well suited for the implementation into elastomeric composites and textiles that are worn close to the human body and have to follow a wide range of movements. In order to overcome this issue, the presented study aims at the development of electrically conductive and elastic filaments based on a coating process suited for multifilament yarns made of thermoplastic polyurethane (TPU). The coating solution contains TPU, carbon nanotubes (CNT) and N-Methyl-2-pyrrolidone (NMP) with varied concentrations of solids and electrically conductive particles. After applying the coating to TPU multifilament yarns, the mechanical and electrical properties are analyzed. A special focus is given to the electromechanical behavior of the coated yarns under mechanical strain loading. It is determined that the electrical conductivity is maintained even at elongations of up to 100%.

Revealing Electrical and Mechanical Performances of Highly Oriented Electrospun Conductive Nanofibers of Biopolymers with Tunable Diameter

The present study outlines a reliable approach to determining the electrical conductivity and elasticity of highly oriented electrospun conductive nanofibers of biopolymers. The highly oriented conductive fibers are fabricated by blending a high molar mass polyethylene oxide (PEO), polycaprolactone (PCL), and polylactic acid (PLA) with polyaniline (PANi) filler. The filler-matrix interaction and molar mass (M) of host polymer are among governing factors for variable fiber diameter. The conductivity as a function of filler fraction (φ) is shown and described using a McLachlan equation to reveal the electrical percolation thresholds (φc) of the nanofibers. The molar mass of biopolymer, storage time, and annealing temperature are significant factors for φc. The Young’s modulus (E) of conductive fibers is dependent on filler fraction, molar mass, and post-annealing process. The combination of high orientation, tunable diameter, tunable conductivity, tunable elasticity, and biodegradability makes the presented nanofibers superior to the fibers described in previous literature and highly desirable for various biomedical and technical applications.

An expansion of the brand and message framing effects on smart health-care clothing

PurposeThe purpose of this study is to examine the effects of brand and message framing on consumers’ evaluations and purchase intentions of smart health-care clothing. The study also examines the mediating effect of consumers’ evaluations on the effects of the brand and message framing on purchase intentions. Design/methodology/approachThrough an experimental approach, a total of 240 US consumers’ evaluation of smart health-care clothing is compared according to the existence of a well-known brand (vs. none) and message framing (technology-focused vs. fashion-focused). FindingsThe results show that consumer evaluation of smart health-care clothing is higher when the product is from a well-known brand, where consumers’ fashion consciousness and health consciousness positively influence such an evaluation as covariates. Message framing, however, did not have an influence that revealed any significant difference between technology-focused and fashion-focused messages. The consumer’s evaluation of smart health-care clothing eventually increased their purchase intentions and mediated the effects of brand on purchase intentions. Originality/valueSmart health-care clothing refers to clothing that measures, records and manages the user’s activity and health status through conductive fibers or sensors that are woven in the clothes. Despite its benefits, smart health-care clothing is still not widely adopted among consumers, except for a few successful examples. Closing this gap, the results of this study provide implications regarding whether and how brand and message framing maximize consumers’ evaluations toward smart health-care clothing, which the developers and marketers of such products can use to increase the product’s market penetration.

Scale production of conductive cotton yarns by sizing process and its conductive mechanism

Conductive yarn is an important component and connector of electronic and intelligent textiles, and with the development of high-performance and low-cost conductive yarns, it has attracted more attention. Herein, a simple, scalable sizing process was introduced to prepare the graphene-coated conductive cotton yarns. The electron conductive mechanism of fibers and yarns were studied by the percolation and binomial distribution theory, respectively. The conductive paths are formed due to the conductive fibers' contact with each other, and the results revealed that the connection probability of the fibers in the yarn (p) is proportional to the square of the fibers filling coefficient (φ) as p ∝ φ2. The calculation formula of the staple spun yarn resistance can be derived from this conclusion and verified by experiments, which further proves the feasibility of produce conductive cotton yarns by sizing process.