Issue No. 2, August

Abstract

In this contribution, the preparation and characterization of new shape-memory epoxy based nanocomposites filled with modified multiwalled carbon nanotubes are reported. The study has been focused on the optimization of the preparation methodology and on the evaluation of the effect of different contents of surface modified carbon nanotubes on the properties and the microstructure of the obtained materials. In particular, dispersion test, infrared spectroscopy, thermogravimetric analysis and bright field transmission electron microscopy have been carried out to analyze the modified filler. Moreover, the obtained nanocomposites have been characterized by morphological analysis, differential scanning calorimetry, thermomechanical analysis and X-ray analysis in order to clarify the effect of the nanofiller on the structure and shape memory properties of the materials.

Abstract

The latest research directions related to the design of protective clothing concern implementation of smart materials, such as shape memory alloys (SMA), that allow for its functionalization which could not be achieved with traditional materials. As a result of the research project, a thermo-mechanical treatment program of a nickel-titanium alloy has been elaborated. This program allows to obtain active elements in a form of conical springs that are characterized by twoway shape memory effect and predestined for implementation into protective clothing. Textile materials with SMA elements intended for clothing protecting against flame, radiant heat and molten splashes have been developed and manufactured. Laboratory tests aimed at evaluation of the obtained shape change effect were performed according to the specially modified testing methodology. The test results indicated that SMA elements caused an improvement of the protective properties of textile materials due to their increased thickness and creation of an additional air layer. On the basis of the achieved results, it can be also stated that protection performance of clothing according to the EN ISO 11612:2015 can be increased from level 1 to level 2 by means of textile materials with SMA elements.

Abstract

The combination of polyelectrolyte microgel technology with conventional functionalisation methods to activate the surface of polyester textiles is an innovative approach towards textiles adaptive to their environment. Biopolymer microgel complexes consisting of soft synthetic pH/thermo-responsive microparticles and natural polysaccharide macromolecules in various combinations serve as a novel textile surface functionalising system. Microgel incorporation into polyester surface layers can be achieved with non-demanding techniques such as UV irradiation. The adaptivity of the functionalised textiles to ambient conditions of varying pH, temperature and relative humidity is expressed by changes in their physicochemical and water management properties. These changes occur within a physiological pH/temperature range of the human body (pH 4-8, 20-40°C), owing to the corresponding stimuli-responsive properties of the functionalising microgels, giving scope for applications in the fields of biomedicine and protective clothing. Indicatively, such changes involve a shift in polyester surface charge from positive to negative values at a pH range 5.0-6.6, following the trend of the incorporated polyelectrolytes. Below 36°C, functionalised textiles exhibit improved water wettability, whilst above 36°C they have lower moisture regain and higher water vapour transmission rates than the non-functionalised textiles. The manifestation of the imparted adaptivity to ambient conditions is also a function of the intrinsic characteristics (e.g. porosity, surface roughness) of the textile, allowing for suitable combinations of substrates and functionalising systems with tailored properties.

Abstract

Electroluminescence offers a versatile and simple route to printed light sources. A layer of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) was inkjet printed onto polyethylene terephthalate (PET) mesh fabrics. The conductivity–transparency relationship is determined for textile-based conductors with different thicknesses of the printed PEDOT:PSS film. Alternating current powder electroluminescent devices were made by extrusion printing a layer of phosphor onto aluminum foil and then covering this with a fabric electrode. These devices are compared with indium tin oxide (ITO) glass electrodes on a similar device. Textiles coated with conducting polymers are a potential alternative to coated polymer films for flexible, transparent conductors. The strain response of these electrodes was improved by incorporating carbon nanotubes into the conductor. These bridge cracks that form on stretching.

Abstract

In order to mimic natural tissues, a successful strategy is to design bio-inspired materials including controlled morphological and biochemical cues as nature guidelines suggested. In this context, old and new process technologies, case by case, have to be adapted to develop innovative templates with the finest control of structural/functional properties able to correctly interact with biological tissues. Since organic and inorganic materials from synthetic or natural source do not singularly satisfy all the requirements, the discovery of new process solutions able to combine two or more materials into multicomponent systems (i.e., blends, composites, hybrids) may represent an interesting alternative for scaffold design. In order to simplify process conditions, without limiting the complexity of final device, current trends mainly address to bottom up approaches based on fibres used as micro-tassels, variously combined as a function of the desired properties – biochemical, mechanical or biological ones, to form the final device.
Here, two different approaches based on the use of polymeric fibres have been proposed. Continuous microfibres processed by capillary extrusion can be integrated as reinforcement agent of porous biodegradable matrices to develop composite scaffolds with multiscale degradation properties suitable for hard tissue regeneration. Alternatively, micro- or submicro- fibres made of synthetic and/or natural polymers can be randomly assembled or patterned to form uniaxially oriented or textured platforms, thanks to the high customization of electrofluidodynamic techniques (i.e., electrospinning). Both approaches offer a large variety of micro and nano-structured platforms - with micro/nanoscale architecture and peculiar chemical composition - suitable as scaffolds or biotextiles for tissue regeneration or other biomedical uses.

Abstract

In this paper we present preliminary results of ballistic testing and thermal measurement of a functional structure consisting of phase change material (PCM) and soft armour layers made of Kevlar. The purpose of this study is to explore the feasibility of combining thermal management with ballistic protection in a single system such that the thermal stress of dismounted combat personnel may be mitigated to an extent while wearing their body armour in hot and humid environments. Under such conditions the breathability of smart textiles will offer little to no benefit. In our study each Kevlar sheet is coated with PCM from Microtek Laboratories Inc. and bonded with normal PVA wood glue. Twenty coated layers were prepared for ballistic testing and compared with twenty pure Kevlar layers as reference. The cooling power of the soft armour insert (SAI) with PCM was measured on a heated sweating manikin. The proof of concept results show that the SAI with PCM only produced a mild cooling effect, which may lower skin temperature and provide a mild cooling sensation for a body region that would otherwise allow limited heat loss, due to the impermeability of the SAI.

Abstract

We report formation of complex responsive fibers consisting of a low molecular weight liquid crystal (LC) core surrounded by a polymer sheath using simple airbrush or jet spraying techniques. The fibers are formed using a solution of LC and polymer dissolved in a common solvent. With proper control of the solution composition and formation conditions the fibers selfassemble. The diameter of the resulting fibers can be adjusted over a range spanning from one to tens of microns. The core of the fiber retains all of the responsive properties associated with low molecular weight LCs. A nematic LC core's director aligns along the long axis of the fiber making them highly birefringent. An electric field applied across the fiber changes both the director alignment and the optical properties of the fiber. Alternatively, thermochromic fibers are formed using a cholesteric LC in the core. Unlike similar electrospun fibers, the airbrushed fibers can be sprayed as continuous mats on virtually any surface or woven into textiles. The resulting fabrics can be made into displays, thermochromic temperature sensors, or for detection of chemical or biological agents. They offer numerous opportunities for wearable textiles that respond optically to a variety of stimuli.

Abstract

Currently electroluminescent devices, operated by alternating current (AC-EL) on film, paper or textile are based on a capacitor with one transparent electrode and one generally nontransparent, highly conductive electrode and a light-emitting dielectric layer in-between. The lightemitting pigments are mostly based on doped zinc sulfide. Currently available commercial products contain encapsulated pigments dispersed in organic solvents. Those dispersions allow AC-ELdevices illuminating solitary in the colors white, green, blue-green, blue and orange. Blending those pigments leads to numerous new colors however, always linked to loss of brightness in the final device. In this research work the combination of fluorescent organic and inorganic dyestuffs with inorganic EL-phosphors was investigated. The AC-EL-devices were all based on textile materials; all dispersions were free of organic solvents. Special focus was directed to the concentration of dyes in an additional layer within the EL-capacitor as well as the thickness and particularly the positioning of the layer. In the result colors were achieved, which cannot be found by blending the phosphors, such as yellow and red. In addition, depending on the type of added fluorescent dyestuff layer, the brightness could be increased substantially.

Abstract

In a near future, many people will be able to visit and stay in the space hotels easier than now days. In this situation, a novel clothes that fit to the special environment will be required. In this paper, we describe the detail of a prototype of “space clothes”, a new clothes design that could solve the appearance and functionality conditions shown below.
• Conventional clothes especially skirts and loosely designed shirts are often difficult to be worn in space because it restricts wearer’s motion. On the other hand, such clothes are often preferred by women because of their elegance. The both elegance and functionality must be achieved for the clothes of the future space tourists.
• All the future space tourists should suffer from space sickness and sunburns by ultraviolet rays.
Those issues will worsen the experience in the space. Future clothes for space tourists should be able to solve or be able to mitigate them.
Based on these conditions, we developed a prototype of clothes for future space tourists.
This clothes is carefully designed to achieve both functionality and elegance. In addition, it embedded with bio-informatics display system to share wearer’s health status among other tourists to enable early initial treatment. We believe that this paper could be a good opportunity to initiate the discussion to clear new market of clothes in space.

Abstract

Electrospinning is a versatile technology for the production of polymer micro/nano scale fibers. It provides the direct addition of bioactive payloads into micro/nanofibers thus improving the encapsulation efficiency and reducing the burst release via proper selection of drug-polymer-solvent system or electrospinning setup. In addition, since electrospun fibers have one dimension at the microscopic scale but another dimension at the macroscopic one, it is possible to combine the advantages possessed by functional materials on the nano-meter scale. A large surface to volume ratio, with the properties of conventional solid membranes, such as ease of manipulation and applicability in any size and shape, making them suitable for biomedical or healthcare applications both topically (i.e. skin) and locally (i.e. tumor). This communication deals with electrospun fibrous systems containing active compounds extracts from plants such as Artemisinin and Propolis; these systems have been properly realized to preserve the pharmacological activity of drugs and evaluated as potential delivery systems for vector-born deseases and cancer, reducing the damage to non-target organism and environment.

Abstract

Alternating-current (AC) electroluminescent (EL) devices on fabrics with high brightness
are presented. The EL-devices were fabricated via knife coating; inorganic luminous pigments are
based on zinc sulfide. Effects of parameters influencing the brightness were investigated. These
parameters are the AC-voltage, AC-frequency, AC-waveform, layer composition of the luminous capacitor and the fabric. Introducing a flexible reflecting dielectric layer enhances the light yield on fine woven fabrics with green luminous pigment. This can be achieved with small concentrations of reflective white pigments such as titanium dioxide, maintaining the flexibility and bendability of the textile substrate. The produced luminous textiles are investigated as a possible replacement for light boxes used in the therapy of seasonal affective disorder (SAD). A high luminous emittance and a high portion of short and energy rich wavelengths are necessary for the treatment. Contrarily to state-of-the-art light boxes a higher acceptance of light therapy is expected, because a luminous textile can be integrated easily and unremarkably into the living environment.

Abstract

Textile band structures with integrated soft condensed matter sensor (SCMS) can be used as a vital function monitor device to detect pulse wave and breathing on the human body. A textile an elastic band was used as a support material and the U-shaped SCMS fiber sensor was bonded on the surface with elastic band with a liquid rubber bonding material. The sensor signal and gauge factor of the textile sensor structure was investigated using tensile testing experiments. The resistivity of the sensor structure increased linearly within a strain of 10 to 50%, and a slope of 8 (kOhm/% strain) could be detected. The sensor had a gauge factor of 4-5 from 10 to 50% between strain. Using the integrated SCMS sensor textile band around the chest, it was possible to detect talking, normal breathing and coughing. In collaboration with Rice University the textile sensor was tested for proof-of-concept for use in a battery-powered monitor for apnea of premature infants.