Flexible rewritable electrochromic device with handwriting feature

Abstract

A rewritable electrochromic device (rECD) was developed to achieve handwriting function. The device was composed of four main components: a flexible conductive substrate, ruthenium-based metallo-supramolecular polymer (polyRu) as an electrochromic layer, electrolyte film, and a stainless steel stylus for writing. To avoid color diffusion between electrochromic pixels, a device structure with separate electrolyte pixels was designed. Next, to achieve handwriting feature without damaging the device, poly (vinylidene fluoride) was mixed with nanocellulose crystals to provide an anti-scratch electrolyte layer. The assembled device was switched between red and transparent states by applying an electrical potential of −0.7 V and +1.0 V, respectively. The rECD exhibited a high coloration efficiency of 332 cm2/C at 525 nm, rapid response times within a second. Moreover, the transmittance change without significant loss after 1000 color/bleach cycles was observed. The flexible rECD can be operated under bending condition without losing coloring ability. We demonstrated a feasible structure of rECD with durable electrolyte pixels for the first time. This strategy can be extended to the other practical handwriting applications.