A polymer-based textile thermoelectric generator for wearable energy harvesting

Conducting polymers offer new opportunities to design soft, conformable and light-weight thermoelectric textile generators that can be unobtrusively integrated into garments or upholstery. Using the widely available conducting polymer:polyelectrolyte complex poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) as the p-type material, we have prepared an electrically conducting sewing thread, which we then embroidered into thick wool fabrics to form out-of-plane thermoelectric textile generators. The influence of device design is discussed in detail, and we show that the performance of e-textile devices can be accurately predicted and optimized using modeling developed for conventional thermoelectric systems, provided that the electrical and thermal contact resistances are included in the model. Finally, we demonstrate a thermoelectric textile device that can generate a, for polymer-based devices, unprecedented power of 1.2 μW at a temperature gradient ΔT of 65 K, and over 0.2 μW at a more modest ΔT of 30 K

Machine-Washable Conductive Silk Yarns with a Composite Coating of Ag Nanowires and PEDOT:PSS

Electrically conducting fibers and yarns are critical components of future wearable electronic textile (e-textile) devices such as sensors, antennae, information processors, and energy harvesters. To achieve reliable wearable devices, the development of robust yarns with a high conductivity and excellent washability is urgently needed. In the present study, highly conductive and machine-washable silk yarns were developed utilizing a Ag nanowire and PEDOT:PSS composite coating. Ag nanowires were coated on the silk yarn via a dip-coating process followed by coating with the conjugated polymer:polyelectrolyte complex PEDOT:PSS. The PEDOT:PSS covered the Ag nanowire layers while electrostatically binding to the silk, which significantly improved the robustness of the yarn as compared with the Ag nanowire-coated reference yarns. The fabricated conductive silk yarns had an excellent bulk conductivity of up to ∼320 S/cm, which is largely retained even after several cycles of machine washing. To demonstrate that these yarns can be incorporated into e-textiles, the conductive yarns were used to construct an all-textile out-of-plane thermoelectric device and a Joule heating element in a woven heating fabric

Roll-to-Roll Dyed Conducting Silk Yarns: A Versatile Material for E-Textile Devices

KGaA, Weinheim Textiles are a promising base material for flexible and wearable electronic applications such as sensors, actuators, and energy harvesters. An essential component in such electronic textiles (e-textiles) is electrically conducting yarns. Here, a continuous dyeing process is presented to convert an off-the-shelf silk sewing thread into a wash and wear resistant functional thread with a conductivity of about 70 S cm−1; a record high value for coated yarns. An aqueous ink based on the conducting polymer:polyelectrolyte complex poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) is modified, to produce more than 100 m of dyed conducting threads, which are subsequently converted into e-textiles by both hand weaving and machine embroidery. The yarns are resistant to abrasion and wear, and can be machine washed at least 15 times with retained electronic properties. The woven fabric is used to design a capacitive touch sensor which functions as an e-textile keyboard

Mechanically Adaptive Mixed Ionic-Electronic Conductors Based on a Polar Polythiophene Reinforced with Cellulose Nanofibrils

Conjugated polymers with oligoether side chains are promising mixed ionic-electronic conductors, but they tend to feature a low glass transition temperature and hence a low elastic modulus, which prevents their use if mechanical robust materials are required. Carboxymethylated cellulose nanofibrils (CNF) are found to be a suitable reinforcing agent for a soft polythiophene with tetraethylene glycol side chains. Dry nanocomposites feature a Young’s modulus of more than 400 MPa, which reversibly decreases to 10 MPa or less upon passive swelling through water uptake. The presence of CNF results in a slight decrease in electronic mobility but enhances the ionic mobility and volumetric capacitance, with the latter increasing from 164 to 197 F cm-3 upon the addition of 20 vol % CNF. Overall, organic electrochemical transistors (OECTs) feature a higher switching speed and a transconductance that is independent of the CNF content up to at least 20 vol % CNF. Hence, CNF-reinforced conjugated polymers with oligoether side chains facilitate the design of mechanically adaptive mixed ionic-electronic conductors for wearable electronics and bioelectronics

Polymer-Based n-Type Yarn for Organic Thermoelectric Textiles

A conjugated-polymer-based n-type yarn for thermoelectric textiles is presented. Thermoelectric textile devices are intriguing power sources for wearable electronic devices. The use of yarns comprising conjugated polymers is desirable because of their potentially superior mechanical properties compared to other thermoelectric materials. While several examples of p-type conducting yarns exist, there is a lack of polymer-based n-type yarns. Here, a regenerated cellulose yarn is spray-coated with an n-type conducting-polymer-based ink composed of poly(benzimidazobenzophenanthroline) (BBL) and poly(ethyleneimine) (PEI). The n-type yarns display a bulk electrical conductivity of 8 7 10−3 S cm−1 and Seebeck coefficient of −79 \ub5V K−1. A promising level of air-stability for at least 13 days can be achieved by applying an additional thermoplastic elastomer coating. A prototype in-plane thermoelectric textile, produced with the developed n-type yarns and p-type yarns, composed of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)-coated regenerated cellulose, displays a stable device performance in air for at least 4 days with an open-circuit voltage per temperature difference of 1\ua0mV\ua0\ub0C−1. Evidently, polymer-based n-type yarns are a viable component for the construction of thermoelectric textile devices

Robust PEDOT:PSS Wet‐Spun Fibers for Thermoelectric Textiles

To realize thermoelectric textiles that can convert body heat to electricity, fibers with excellent mechanical and thermoelectric properties are needed. Although poly(3,4‐ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) is among the most promising organic thermoelectric materials, reports that explore its use for thermoelectric fibers are all but absent. Herein, the mechanical and thermoelectric properties of wet‐spun PEDOT:PSS fibers are reported, and their use in energy‐harvesting textiles is discussed. Wet‐spinning into sulfuric acid results in water‐stable semicrystalline fibers with a Young\u27s modulus of up to 1.9 GPa, an electrical conductivity of 830 S cm−1, and a thermoelectric power factor of 30 μV m−1 K−2. Stretching beyond the yield point as well as repeated tensile deformation and bending leave the electrical properties of these fibers almost unaffected. The mechanical robustness/durability and excellent underwater stability of semicrystalline PEDOT:PSS fibers, combined with a promising thermoelectric performance, opens up their use in practical energy‐harvesting textiles, as illustrated by an embroidered thermoelectric fabric module

Electrically Conducting Yarns for Electronic Textiles

Electronic textiles (e-textiles) present a huge opportunity to incorporate wearable devices into textiles. Electrically conducting yarns and fibers can be utilized to create these e-textiles. For e-textiles to be wearable the development of electrically conducting yarns needs to rely on materials that are neither scares nor toxic. Certain functionalities are required for the conducing yarns which depends on the e-textile application. We have therefore explored different conducting materials, substrates, and various e-textiles devices to investigate vital conducting yarn properties. This thesis discusses the different conducting yarns and what textile processes have been used to make textile thermoelectric devices, organic electrochemical transistors, and Joule heating elements. Specifically, our PEDOT:PSS coated cellulose yarn that displays a, for cellulose, record-high bulk conductivity 36 Scm-1 is presented. The characterization of electrical and mechanical properties for yarns are also explored in this thesis. The durability of the PEDOT:PSS coated yarn was illustrated by showing that the yarn could be machine washed at least five times without conductivity loss. And the resilience was further exemplified by using a household sewing machine to make an out-of-plane thermoelectric textile device

Electrically Conducting Cellulose Yarns for Electronic Textiles

Wearable electronics can be used for the purpose of fitness tracking, health monitoring, energy harvesting, and even for communication. Electronic textiles (e-textiles) are a versatile platform which can be employed for the realization of wearable electronics. E-textiles present an opportunity to incorporate electronics into textiles while also maintaining the feel and wearability of textile materials. To fabricate e-textile devices, electrically conducting yarns can be used as building blocks. It is of importance to use materials that are lightweight, benign, and scalable to enable the widespread use of e-textiles. Electrically conducting yarn can be produced by combining conducting, semiconducting and insulating materials. For energy harvesting applications, textile thermoelectric generators are of interest since these can utilize the temperature gradient between the body and the ambient surroundings to generate electrical energy.This thesis discusses several strategies for the development of electrically conducting yarns, which were based on conducting polymers and regenerated cellulose yarns. Hole- and electron-transporting conducting polymer-based yarns were realized for the fabrication of textile thermoelectric generators. Various methods to characterize conducting yarns were explored to evaluate properties of interest for e-textile devices, such as procedures for measuring the electrical resistance and the Seebeck coefficient of the yarns. Furthermore, the electrical stability of the yarns was investigated upon washing and bending, to assess if the produced yarns could withstand textile processing and use. Several p-type polymer-based yarns were produced. P-type polymer-based coated cellulose yarns that were generated through a roll-to-roll process showed a record-high bulk conductivity of 36 S cm-1 for cellulose based conducting yarn. The durability was demonstrated by machine sewing the yarns into a substrate fabric for thermoelectric device fabrication. Furthermore, this thesis introduces the first example of n-type polymer-based yarns, which were produced by spray-coating regenerated cellulose yarns. The p-type and n-type polymer-based coated cellulose yarns enabled the fabrication of an all polymer-based thermoelectric textile device.The presented methods are scalable and resulted in conducting yarns with resilient electrical properties that could be used for the fabrication of e-textile devices. The demonstrated conducting polymer-based yarns present new opportunities for further development of textile polymer-based thermoelectric generators

Huge potential for electronic textiles made with new cellulose thread

Electronic textiles offer very interesting new opportunities in various fields, in particular in healthcare. However, to be sustainable, they need to be made of renewable materials. A research team led by Chalmers University of Technology, Gothenburg/Sweden, now presents a thread made of conductive cellulose, which offers interesting and practical possibilities for electronic textiles

Highly Reliable Yarn-Type Supercapacitor Using Conductive Silk Yarns with Multilayered Active Materials

The fibrous supercapacitor is a promising candidate for wearable energy-storage systems due to excellent mechanical reliability under deformation. In this study, a mechanically reliable fibrous supercapacitor with high volumetric power density and energy density was developed using fiber electrodes composed of multilayered active materials coated on silk yarns. The conductive silk yarn electrodes are fabricated via a sequential dip-coating process of silver nanowires, multi-walled carbon nanotubes (MWCNT, three to seven walls), and poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS). The composite-coated silk yarn electrodes were stable under cyclic bending as well as under washing in water. Due to the synergetic effect of the three conducting materials, an excellent electrochemical performance was obtained resulting in high volumetric energy and power densities of 8–13 mWh cm−3 and 8–19\ua0W cm−3, respectively. A yarn-type supercapacitor was demonstrated by integrating composite-coated silk yarn electrodes with a hydrogel electrolyte, showing a promising stability as evidenced by the retention of over 94% and 93% of the specific capacitance after 90-degree bending and stretching