Anja Lund

Machine-Washable PEDOT:PSS Dyed Silk Yarns for Electronic Textiles

Durable, electrically conducting yarns are a critical component of electronic textiles (e-textiles). Here, such yarns with exceptional wear and wash resistance are realized through dyeing silk from the silkworm Bombyx mori with the conjugated polymer:polyelectrolyte complex PEDOT:PSS. A high Young’s modulus of approximately 2 GPa combined with a robust and scalable dyeing process results in up to 40 m long yarns that maintain their bulk electrical conductivity of approximately 14 S cm–1 when experiencing repeated bending stress as well as mechanical wear during sewing. Moreover, a high degree of ambient stability is paired with the ability to withstand both machine washing and dry cleaning. For the potential use for e-textile applications to be illustrated, an in-plane thermoelectric module that comprises 26 p-type legs is demonstrated by embroidery of dyed silk yarns onto a piece of felted wool fabric.

Textile sensing glove with piezoelectric PVDF fibers and printed electrodes of PEDOT:PSS

The development of an entirely polymer-based motion sensing glove with possible applications, for example, in physical rehabilitation is described. The importance of comfort for the wearer and the possibility to clean the glove in normal laundering processes were important aspects in the development. The glove is all textile and manufactured using materials and methods suitable for standard textile industry processes. For the first time, melt-spun piezoelectric poly(vinylidene fluoride) (PVDF) fibers with conductive cores were machine embroidered onto a textile glove to function as a sensor element. Electrodes and electrical interconnections were constituted by a screen printed conductive poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) formulation. The screen printing of the interconnections was shown to be a reliable method for reproducible material deposition, resulting in an average surface resistivity value of 57 Ω/square. A repeated strain of 10% only influenced the resistance of the interconnections initially and to a very limited extent. The influence of washing on the electrical resistance of the printed interconnections was also studied; after 15 wash cycles the average surface resistivity was still below 500 Ω/square, which was deemed sufficient for the polymeric sensor system to remain functional during long-term use. Sensor data from the glove was also successfully used as input to a microcontroller running a robot gripper, in order to demonstrate its potential applications.

Energy harvesting textiles for a rainy day: woven piezoelectrics based on melt-spun PVDF microfibres with a conducting core

Recent advances in ubiquitous low-power electronics call for the development of light-weight and flexible energy sources. The textile format is highly attractive for unobtrusive harvesting of energy from e.g., biomechanical movements. Here, we report the manufacture and characterisation of fully textile piezoelectric generators that can operate under wet conditions. We use a weaving loom to realise textile bands with yarns of melt-spun piezoelectric microfibres, that consist of a conducting core surrounded by β-phase poly(vinylidene fluoride) (PVDF), in the warp direction. The core-sheath constitution of the piezoelectric microfibres results in a—for electronic textiles—unique architecture. The inner electrode is fully shielded from the outer electrode (made up of conducting yarns that are integrated in the weft direction) which prevents shorting under wet conditions. As a result, and in contrast to other energy harvesting textiles, we are able to demonstrate piezoelectric fabrics that do not only continue to function when in contact with water, but show enhanced performance. The piezoelectric bands generate an output of several volts at strains below one percent. We show that integration into the shoulder strap of a laptop case permits the continuous generation of four microwatts of power during a brisk walk. This promising performance, combined with the fact that our solution uses scalable materials and well-established industrial manufacturing methods, opens up the possibility to develop wearable electronics that are powered by piezoelectric textiles.Wearable electronics: textile piezoelectric generators made washableCore-sheath design shielding the inner electrodes brings the washable function and boosts the performance of the piezoelectric generators.A collaborative team led by Christian Müller from Chalmers University of Technology, Sweden presents piezoelectric generator based on textiles made of core-sheath structured polymer microfibers. The black carbon/polyethylene based hidden electrodes are coated with piezoelectric polymer PVDF by a melt spinning process and then woven into textile bands with PA silver conducting yarns as the outer electrodes. Such a design guarantees the water proof function and even improves the performance with water due to reduced resistance. As a result, a 2.5 cm × 20 cm textile delivers an output pulse voltage of up to 8 V under wet conditions and continuous output power of 4 µW in a brisk walk.

All-Organic Textile Thermoelectrics with Carbon-Nanotube-Coated n-Type Yarns

Thermoelectric textiles that are able to generate electricity from heat gradients may find use as power sources for a wide range of miniature wearable electronics. To realize such thermoelectric textiles, both p- and n-type yarns are needed. The realization of air-stable and flexible n-type yarns, i.e., conducting yarns where electrons are the majority charge carriers, presents a considerable challenge due to the scarcity of air-stable n-doped organic materials. Here, we realize such n-type yarns by coating commercial sewing threads with a nanocomposite of multiwalled carbon nanotubes (MWNTs) and poly(N-vinylpyrrolidone) (PVP). Our n-type yarns have a bulk conductivity of 1 S cm–1 and a Seebeck coefficient of −14 μV K–1, which is stable for several months at ambient conditions. We combine our coated n-type yarns with poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) dyed silk yarns, constituting the p-type component, to realize a textile thermoelectric module with 38 n/p elements, which are capable of producing an open-circuit voltage of 143 mV when exposed to a temperature gradient of 116 °C and a maximum power output of 7.1 nW at a temperature gradient of 80 °C.