Smart textiles combine the features of conventional textiles with promising properties of smart materials such as electromechanically active polymers, resulting in textile actuators. Textile actuators comprise of individual yarn actuators, so understanding their electro-chemo-mechanical behavior is of great importance. Herein, this study investigates the effect of inherent structural and mechanical properties of commercial yarns, that form the core of the yarn actuators, on the linear actuation of the conducting-polymer-based yarn actuators. Commercial yarns were coated with poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) to make them conductive. Then polypyrrole (PPy) that provides the electromechanical actuation is electropolymerized on the yarn surface under controlled conditions. The linear actuation of the yarn actuators is investigated in aqueous electrolyte under isotonic and isometric conditions. The yarn actuators generated an isotonic strain up to 0.99% and isometric force of 95 mN. The isometric strain achieved in this work is more than tenfold and threefold greater than the previously reported yarn actuators. The isometric actuation force shows an increase of nearly 11-fold over our previous results. Finally, a qualitative mechanical model is introduced to describe the actuation behavior of yarn actuators. The strain and force created by the yarn actuators make them promising candidates for wearable actuator technologies. © 2023 The Authors. Advanced Materials Technologies published by Wiley-VCH GmbH.

Smart textile is a term referring to the textiles that could interact with their environment, receiving input and giving output based on their applications. Among smart textiles, electrically driven smart textiles (E-textiles) are being produced by various methods and materials integrated with textile substances. Graphene is one of these compounds that could be integrated into the polymer or integrated into the textile materials such as fibres. Therefore, other elements could be doped or immobilised on the graphene nanosheets for a wider range of applications, such as catalytic and electrocatalytic systems.  

However, finding the most applicable and efficient method to integrate graphene into the textile fibres and further establishing a method for catalyst immobilisation are challenging and require focused research.  

Therefore, this doctoral thesis focused on the innovative concept of integration of graphene and immobilisation of iron nanoparticles on it. Evidence from the systematic experiments was gathered for the case of dip-coating of polyester textiles with graphene oxide dispersion and enhancing the electrostatic bonding between fibres and graphene oxide nanosheets. In the second step, systematic experiments were gathered for the case of immobilisation of an inorganic catalyst (zerovalent iron) on textile supports. The goal of this thesis is to establish the feasibility of a mild and applicable method for textile material supports, which requires low temperature and mild pH, and further fabrication of heterogeneous catalytic and electrocatalytic systems for wastewater treatment. Polyester was chosen as the textile support material for graphene oxide coating and catalyst immobilisation due to its availability and cost-effectiveness.  

The thesis has four distinct parts related to (a) Pre-surface-charge modification of the polyester for strong electrostatic bonding between polyester and graphene, (b) Design a continuous yarn coating system for mass production of graphene-coated conductive yarns, (c) Immobilisation of Fe0 on graphene-coated polyester textiles and optimising their feasibility in catalytic systems and (d) Design and prove the feasibility of knitting a fully textile-based reactor having two anodic and cathodic sections by using rGO-Fe0 yarns and stainless-steel multifilament yarns, respectively as a concept of electro-Fenton wastewater treatment.  

Diverse analytical and instrumental techniques were used to monitor the surface modification of the polyester textiles and conductivity of the resulting textiles; moreover, the electromechanical and electrothermal properties of the graphene-modified textiles were examined. Further, the efficiency of catalyst immobilisation, physio-chemical properties of the immobilised catalyst, and their catalytical activities in dye removal from the water was studied. Results showed that surface charge modification of polyester fabric with both chitosan and hexadecylpyridinium chloride (HDPC) gives the most homogeneous graphene coating, resulting in high conductivity and very good fastness. Furthermore, results from scanning electron microscope (SEM), Differential scanning calorimetry (DSC), and UV/Visible spectrophotometry prove the success of immobilisation of zerovalent iron on the graphene-modified textiles. 

The novelty of the research presented in this doctoral thesis is primarily attributed to the novelty of a hybrid graphene-catalyst immobilisation-grafting on polyester textile supports for wastewater treatment applications. The final concept of the thesis is to introduce the potential for assembling a fully textile-based reactor for Electro-Fenton wastewater treatments.

A graphene/Fe loaded polyester fabric-PET with high electrical and catalytic properties has been successfully developed for the first time, via simple coating-incorporation method using hyperbranched poly(amidoamine)-PAMAM dendrimer as binder. Both graphene oxide (GO/rGO) and zerovalent iron (Fe⁰) nanoparticles were loaded on polyester fabric surface before and after chemical grafting of PAMAM.  Full characterization of fabrics before and after modifications has been studied through sessile droplet goniometry, ζ–potential, K/S coating evenness, SEM, XPS, FTIR, TGA and DSC analysis. Results showed successful and uniform coating of GO/rGO and loading of Fe⁰ on PET; also allowed correlating the type of chemical moiety responsible for uniform GO coating, high Fe⁰ loading and their electrical and catalytic activities. Sheet resistance (R_sh) analysis was carried out to measure the conductivity of the samples. The lowest R_sh (corresponds to high conductivity) has been found in PET-PAM-rGO-Fe⁰ (0.74±0.13 kΩ/sq) followed by PET-rGO-Fe⁰ (1.32±0.18 kΩ/sq), PET-PAM-rGO (2.96±0.08 kΩ/sq) and PET-rGO (3.41±0.34 kΩ/sq). Furthermore, Fe⁰ –loaded samples were found to be effective in catalytic removal of toxic water pollutants (crystal violet dye) with ~99% removal of pollutants in around one hour, as observed by UV-vis spectroscopy. Relatively high electrical and catalytic activity in PET-PAM-rGO-Fe⁰ is related to the role played by PAMAM in uniform rGO coating and high Fe⁰ loading. These findings are of great importance as they allow envisaging the development of multifunctional textiles for combined smart and green chemistry application.

Recently, graphene has been used to obtain (E)-textiles. From an industry-relevant perspective, it is essential to introduce a process that could be scaled-up. We applied a cost-effective dip-coating method using bio-sourced agents for chemical adsorption of graphene oxide (GO). Polyester and viscose woven fabrics were treated with an aqueous solution of glycerol (4 g.L-1) to overcome the electrostatic repulsion among fibers and GO and then dip-coated with a dispersion of GO. The results are homogeneous GO coating with one to a few layers of GO nano-sheets. Further, The GO was chemically reduced to rGO, by using tannic acid (10 g.L-1) as a bio-sourced reducing agent. This brings electrical conductivity to rGO nano-sheets having an electrical resistance of 2±1 and 10±4 kΩ/sq for polyester and viscose fibers respectively. Afterward, these E-textiles are both p-type and n-type doped, using nitrogen plasma treatment to prepare nitrogen-doped graphene as a p-type E-textile and electrochemical deposition of titanium on graphene as n-type Doped E-textiles. This increases the charge carrier density, consequently increasing the conductivity of the graphene. Doping rGO-modified textiles open up a visualization of the p-n junction fully-textile diodes and its further applications.

Smart textiles, a part of the present boom of wearables, is at the risk of being a newenvironmental problem as many axioms of sustainability are violated here, that of driving(mass) consumption, mixing of components of different material origin and no obvious wastehandling system when used and worn out. Smartness has been synonymous with integration ofelectronic conductivity functionality, typically realised by metal wires. Carbon allomorphsshowing low electrical resistivity might be an environmental friendly alternative.

Here we report on attempts with simple conductive graphite systems from which we makeconductive textile fibres, the production of which could be up-scaled to industrial volumes.Coating textile bulk fibers as polyester, polyamide, wool and cellulose based regenerate onesrather than (melt/wet) spinning new fibers, the mechanical properties are sustained makingthem processable within existing textile processes infrastructure.

Several different graphite compositions and different yarn topologies are compared. Twisting isshown to greatly increase the overall yarn conductance. Fabrics are manufactured with thegraphite yarns in the double role of being structural as well as functional. Furthermore, analphabet of fundamental electrical circuitry elements are demonstrated; conductor, capacitor,inductor. The devices are consisting of non-toxic components that are disposable andcompostable; showing the benefits of carbon based soft electronics.

Conjugated polymers have been developed over the last decade for applications as artificial muscle. These polymers can be synthesized on the conventional yarns to prepare actuators. When a single yarn is functionalized with such polymers, the isotonic generated strain is very low  (around 0.075%). In order to reach the early stages of commercialisation, especially in exo-skeleton devices, it is critical to amplify the actuation mechanism in both isometric force transfer and strain generation. In our previous study we showed that by using a 2´1 rib knitted fabric as a viscoelastic substrate, the generated strain enhances to 3%.

However, viscoelastic properties of fabrics are determined not only by the constitutive operators of the fibers but also by the fabric pattern and its structures, which governs the fibre deformation. Here we have studied the actuation mechanism of polypyrrole on various fabric structures.

Polyamide 6 and stretchable polyamide 6/PU fibers were used to knit the fabrics. Fabrics were pre-modified with tannic acid and bath sonicated for its stress relaxation. Then, they were dip-coated in PEDOT:PSS solution in order to achieve an electrode layer. Dynamic elastic behaviour of samples was measured before and after applying the seed layer. Further, electrochemical synthesis of polypyrrole on PEDOT:PSS was taken place by a 3-electrode electrochemical cell setup. A dual-mode muscle lever was used to characterize the textile actuators. The results show that the efficiency of actuation mechanism is determined by both viscoelastic properties and stress-relaxation time of textiles.

Graphene has the potential to create highly valuable electrical conductive textile systems with maintained pliability and psychological comfort. There have already been numerous studies regarding electrically functionalized graphene-coated textiles. However, processing development is far from being exhausted. Here we have studied electro-thermal textiles based on the most common fibers, polyester, and an industry-relevant graphene impregnation method by introducing surface pre-modification of fabrics for graphene-modified textile processing. For this purpose, polyester fabrics were treated with four different cationic agents and impregnated with graphene oxide (GO) colloidal particles. Then, direct chemical reduction of GO to an electrically conductive graphene oxide (rGO) was performed. A pristine fabric modified by rGO showed a high resistance of 27.3 kΩ □−1 without any electro-thermal activity, whilst chitosan-treated (CS) and hexadecylpyridinium chloride-treated (HDPC) fabrics had resistance values of 2.7 and 0.59 kΩ □−1 respectively, and excellent heat propagation with a good temperature distribution. The steady-state temperature of CS-treated and HDPC-treated fabrics increased from 28 °C and 33 °C to 60 °C and 120 °C, respectively, as the voltage applied increased from 10 V to 30 V. These rGO-modified fabrics also have excellent electro-mechanical performance, and are good candidates for flexible strain sensor applications.

Diseases of the nervous system, traumas, or natural causes can reduce human muscle capacity. Robotic exoskeletons are forthcoming to support the movement of body parts, e.g. assist walking or aid rehabilitation. Current available devices are rigid and driven by electric motors or pneumatic actuators, making them noisy, heavy, stiff and noncompliant. We are developing textile based assistive devices that can be worn like clothing being light, soft, compliant and comfortable. We have merged advanced textile technology with electroactive polymers. By knitting and weaving electroactive yarns, we are developing soft textile actuators ("Knitted Muscles") that can be used in wearable assistive devices. We will present the latest progress increase the performance and to rationalise the fabrication. In addition we will show some demonstrators of the textile exoskeletons.

Textiles with electrical properties, known as e-textiles, are realized by different methods. Among these, graphene-coated textiles have attracted great attention due to its multifunctional properties such as being flexible lightweight; and offering interesting optical and electrical properties. While Aqueous dispersion of graphene oxide (GO) could be prepared and applied as a dye to textiles via a simple and cost-effectivene dip-coating method. Moreover, the GO could be reduced to graphene directly on the surface of the textiles. However, the GO flakes do not adhere properly to most textiles at any pH values probably because of electrostatic repulsion between the particles and the textile substrate as both the aqueous solution of GO and most textiles carry negative surface charges. Though, GO flakes could be easily assembled on a positively charged surface. Therefore, textiles need to be cationized before the dip-coating in the GO dispersion. In this work a number of both organic and inorganic cationic agents such as chitosan, Poly(diallyldimethylammonium chloride), Hexadecylpyridinium chloride, and Polyethylenimine are applied to the textiles before the coating process. Further on the so formed systems are characterized by scanning electron microscopy, FT-IR measurement, four-terminal sensing surface resistance measurement, diffusion reflection spectroscopy, electro-thermal analysis, and electro-mechanical analysis. The results display the fact that utilizing an appropriate cationic agent not only enhances the absorption of GO onto the textile surfaces but also play a critical role for the electrical conductivities and electro-thermal properties of the coated fabrics, with values varying between 12 to 0.6 kΩ.cm^-1.