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 byβ-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.

Highly insulating thermoplastic blends comprising a styrenic copolymer for direct‐current power cable insulation

The impact of the composition of blends comprising low‐density polyethylene(LDPE),isotactic polypropylene(PP)and a styrenic copolymer additive on the thermomechanical properties as well as the direct‐current(DC)electrical and thermal conductivity is investigated.The presence of 5 weight percent(wt%)of the styrenic copolymer strongly reduces the amount of PP that is needed to enhance the storage modulus above the melting temperature of LDPE from 40 to 24 wt%.At the same time,the copolymer improves the consistency of the thermomechanical properties of the resulting ternary blends.While both the DC electrical and thermal conductivity strongly decrease with PP content,the addition of the styrenic copolymer appears to have little influence on either property.Evidently,PP in combination with small amounts of a styrenic copolymer not only allows to reinforce LDPE at elevated temperatures but also functions as an electrical conductivity‐reducing additive,which makes such thermoplastic ternary formulations possible candidates for the insulation of high‐voltage power cables.