Development of 7-Segment Numeral Display Using Electrochromic Yarns for Advanced Functional Textiles

Development of electrochromic yarns opens up a high-tech option for the development of next-generation fashion textiles. Previous work has introduced electrochromic yarns comprising a metal wire core wrapped with organometallic compounds and conjugated polymers, but has reported unsatisfying colour-changing contrast and weavability. Here we report a tungsten trioxide (WO3)-electroplated high-contrast electrochromic filament suitable for weaving, and a 7-segment display embroidered with such filaments. The electroplating conditions have been optimised through elemental analysis via X-ray photoelectron spectroscopy (XPS), with the aid of coating morphology observation via scanning electron microscopy (SEM). We have learnt that sufficient WO3 for an evident change of colour can be deposited on the filament surface at -0.5V (vs. AgCl) in 30s. This low voltage and short coating duration have shown possibility for up scaled production of the electrochromic filament. Connecting the 7-segment display with ESP8266 Wi-Fi micro-controller unit, through remote signal input on ‘Blynk’ (an open-access mobile platform), we have demonstrated a double-digit ‘chance of rainfall’. Our study offers guidance on the design of textile-based information displays.

Keywords: Electrochromism; 7-segment display; Functional textiles; Tungsten trioxide (WO3)

Abbreviations: XPS: X-ray Photoelectron Spectroscopy; SEM: Scanning Electron Microscopy, ITO: Indium-doped Tin Oxide; TTIP: Titanium (IV) Iso-Propoxide; LD: Lethal Doses; SPA66: Shieldex® polyamide 6.6; SPA6: Shieldex® Polyamide 6; SSF: Stainless Steel Filament; PE-AL: Polyester 66wt%-aluminium 34wt%