Muriel Rigout

All inkjet-printed graphene-based conductive patterns for wearable e-textile applications

Inkjet printing of graphene inks is considered to be very promising for wearable e-textile applications as benefits of both inkjet printing and extra-ordinary electronic, optical and mechanical properties of graphene can be exploited. However, the common problem associated with inkjet printing of conductive inks on textiles is the difficulty to print a continuous conductive path on a rough and porous textile surface. Here we report inkjet printing of an organic nanoparticle based surface pre-treatment onto textiles to enable all inkjet-printed graphene e-textiles for the first time. The functionalized organic nanoparticles present a hydrophobic breathable coating on textiles. Subsequent inkjet printing of a continuous conductive electrical path onto the pre-treated coating reduced the sheet resistance of graphene-based printed e-textiles by three orders of magnitude from 1.09 × 106 Ω sq−1 to 2.14 × 103 Ω sq−1 compared with untreated textiles. We present several examples of how this finding opens up opportunities for real world applications of printed, low cost and environmentally friendly graphene wearable e-textiles.

Novel One Bath Application of Oil and Water Repellent Finish with Environment Friendly Cross-linker for Cotton

The performance of the fluorocarbon based acrylate polymer, Genguard, was evaluated on cotton fabric. Genguard treated fabric exhibited good oil and water repellency rating before washing. However, rating was lost immediately after washing. In order to enhance the washing durability of the Genguard finish, citric acid was incorporated into the recipe as a formaldehyde free cross-linker. The combination of citric acid with fluorocarbon exhibited good improvement in the durability of the oil and water repellency rating after multiple washings. In addition, fabric treated with this novel combination demonstrated excellent increase in the easy care performance. Scanning electron microscope (SEM) was used to examine the surface of the fabric treated with Genguard and citric acid as a cross-linker.

Optimization of the process variables for electrospinning of poly(ethylene oxide)-loaded hydroxypropyl-β-cyclodextrin nanofibres

Electrospinning is a versatile method for making nanofibres from polymer solution. Hydroxypropyl-β-cyclodextrin (HP-β-CD) is electrospun from aqueous solution by blending with non-toxic, biocompatible, synthetic polymer poly(ethylene oxide) (PEO). The aqueous solutions containing 70:30 HP-β-CD/PEO polymer blend with 8 wt.% concentration were electrospun to study the effects of process parameters on fibre morphology. Electrospinning was carried out at variable feed rate, applied voltage and working distance to see the effects on process stability and fibre diameter. Scanning electron microscope images showed that increasing feed rate, applied voltage and working distance promote bead formation in the fibre. The average diameter of the nanofibres was measured using ImageJ software. It was observed that the fibre diameter increased with increasing the feed rate and applied voltage. In contrast, the diameter of the fibres decreased with increasing the working distance up to a certain level. Further increase of the working distance produced beaded fibres. The ultimate objective of this study was optimize the electrospinning parameters to obtain bead-free HP-β-CD/PEO nanofibres. The results revealed that a feed rate of 0.5–1.0 ml/h, a working distance of 10–14 cm and an applied voltage of 5–7 kV have been found to produce smooth PEO loaded HP-β-CD nanofibres.

Investigation into the removal of an easy-care crosslinking agent from cotton and the subsequent regeneration of lyocell-type fibres

Dimethylol dihydroxyethylene urea (DMDHEU)-treated cotton fabrics were treated with alkali or alternatively acid followed by alkali for increasing time periods, and their effectiveness in removing the crosslinking agent was investigated by surface (X-ray photoelectron spectroscopy) analysis, bulk analysis, crease recovery angle performance and solubility in specific solvents. The cellulose yield after the chemical stripping processes was established and the effect of the acid and alkali treatments on the degree of polymerisation of the resultant cellulose determined. Surface and bulk analyses and solubility tests suggested that alkali alone could not remove the DMDHEU from the crease-resist-treated cotton fabric. However, a sequential acid/alkali treatment effectively removed the easy-care finish from the cotton fabric and produced a commercially viable yield of cellulose.

Fabrication and photoluminescence of hyperbranched silicon nanowire networks on silicon substrates by laser-induced forward transfer

The structure and photoluminescent properties of films obtained by modified laser-induced forward transfer of silicon are presented. Strong variations in structure with ambient gas composition are observed: in Ar, porous films of mutually agglomerated silicon nanoparticles are observed, while in air the films consist of a network of hyperbranched nanowires (SiHBNWs) whose diameter varies periodically along their length, and which are composed of crystalline silicon nanoparticles surrounded and interconnected by amorphous silicon oxide of varying stoichiometry. The mechanisms of formation of the structures are dwelt upon and explained in term of dynamics within the plume. For the SiHBNWs, the pioneering use of fluorescence imaging was employed to obtain evidence for the photoluminescence originating from the crystalline nanoparticles themselves, and origins of the emission bands are thus attributed to radiative recombination of excitons at the Si/SiO(2) interface accordingly.

Optical properties of cotton and nylon fabrics coated with silica photonic crystals

In this work, colourant-free coloured fabrics have been produced by the self-assembly of silica nanoparticles (SNPs) using a natural sedimentation method. The optical properties of the SNP-coated fabrics were investigated and the spectral reflectance, chromaticity coordinates, and CIE L* a* b* values are reported. The overall colour effect on the fabric can be described by Bragg’s diffraction of the ordered SNP photonic crystal and the Mie scattering of the disordered SNP arrangement. It was found that the structural colour on the tight black woven cotton fabric was more uniform than that from the loose black knitted nylon fabric. Although the structural colour was not easily perceived on a white fabric due to the strong reflection of the white background, the SEM images show that an ordered photonic crystal was formed on the fabric and a small colour difference by the introduction of SNPs was measured using instrumental colour measurement.

Influence of nanotube dispersion and spinning conditions on nanofibre nanocomposites of polypropylene and multi-walled carbon nanotubes produced through ForcespinningTM

Melt centrifugal spinning has been used to successfully produce nanofibres from compounds of polypropylene (PP) and multi-walled carbon nanotubes (MWNTs) at a concentration of 1%. The compounds were prepared either via twin screw compounding or by dissolution in decalin with sonication. Nanofibre production was conducted by centrifugal spinning in a Forcespinner™, a technology capable of producing nanofibres with a high material throughput. Processing via dissolution resulted in a reduction in the size of the MWNT agglomerations in the polymer, which led to a more uniform fibre morphology and a reduced incidence of bead defects as compared to products produced from the melt extrusion compound. The addition of a nonionic surfactant (Triton X-100) to the compound solution aided dispersion of the MWNTs as determined by optical light microscopy of thin cast films and produced fibres with the lowest mean diameter. The mean fibre diameter in the as-spun webs prepared by dissolution of PP in decalin with sonication was found to decrease with increasing spinneret speed; however, a similar trend was not observed for fibres generated from the melt compounded material.

Development of zero formaldehyde easy care finishing system by using nano titanium dioxide with citric acid and its impact on physical properties

The Performance of nano TiO2 with citric acid cross-linker was assessed by using pad-dry-cure method on cotton fabric. Significant increase in crease recovery performance was observed which was previously only associated with the lengthy ultraviolet irradiation process. The optimum amount of only 0.1 % nano TiO2 was needed with the citric acid to exhibit significant increase in easy care performance of the fabric. Typically, application of a cross-linker to cellulosics will impart a deleterious effect on the softness of the fabric; however, incorporation of nano-TiO2 with the citric acid cross-linker significantly improved the softness of the fabric which was reflected in the mean deviation of coefficient of friction (MMD) and interyarn friction (2HG5) KES-F values. In addition, there was improvement in tensile strength retention of the fabric as well.

Investigation into the removal of a formaldehyde-free easy care cross-linking agent from cotton and the potential for subsequent regeneration of lyocell-type fibres

1,2,3,4-Butane tetracarboxylic acid (BTCA)-treated cotton fabrics were immersed in alkali for increasing time periods and the effectiveness of alkali in removing the cross-linking agent was investigated by surface (X-ray photoelectron spectroscopy, XPS) analysis, attenuated total reflectance Fourier transform infrared spectroscopy and solubility in specific solvents. The cellulose yield after the chemical ‘stripping’ processes was established and the effect of the alkali treatments on the degree of polymerization of the resultant cellulose determined. Surface analyses and solubility tests suggested that the alkali alone could successfully remove the BTCA from the crease resist-treated cotton fabric and produced a commercially viable yield of cellulose.

Towards UV-curable inkjet printing of biodegradable poly (lactic acid) fabrics

There has been growing interest in using poly (lactic acid) (PLA) fibres because of its natural-based origin and good biodegradability; however, its adoption within the textile industry has been limited to lower temperature wet and dry processing, because of its relatively lower glass transition temperature (Tg) and melting point (Tm). Here we report for the first time inkjet printing of heat-sensitive PLA fabrics using ambient temperature UV-curable inks as a way of overcoming the potential degradation at higher temperature. The UV cured inkjet printed PLA fabrics exhibited good performance characteristics such as acceptable colour fastness, relatively high colour strength, K/S, and comparable colour difference, ΔE, after washing to the thermally cured ink system, without affecting the physical and mechanical properties of the fabrics. In contrast thermally cured inkjet printed PLA fabrics exhibited significantly reduced bursting strength and stiffer handle attributed to the thermal degradation and lower fibre flexibility imparted at the higher temperature. Investigation of the radiation-cured printing approach indicates UV-curable inkjet printing may be considered as an alternative to conventional thermally cured pigment printing of heat-sensitive biodegradable PLA-based fabrics.