Fig. 4: Structure, optical properties, and degradation of the BECD with 45 s-electrospun W/PLGA (~75%T and ~ 890 Ω sq^–1).

a An exploded view of the BECD. The BECD is composed of a TCE made of W nanomesh deposited on electrospun PVA template followed by transferring to PLGA, an electrochromic layer made of WO₃ which exhibited a color transition from transparent to deep blue through a Na⁺ ion intercalation, and a solid-electrolyte made of NaCl 1 M agarose hydrogel with Na₄Fe(CN)₆ that lowers the operating voltage and reduces side reactions. b Transmittance change of the BECD at 656 nm wavelength during sweeping potential from 0 V to –1.2 V (coloration, red) and from –1.2 V to 1 V (bleaching, blue). c Transmittance spectra in range of 300 to 700 nm wavelength of the BECD with applied voltage of 0 V (black), –0.4 V (red), -0.8 V (blue), -1.2 V (yellow), and 1 V (green). Vivid and thick colored lines are average data, and pale colored area is standard deviation data (n = 4). d Photographic images at on/off states of the BECD on white paper (left is an initial state and right is on state which applying –1.2 V) (Aperture F 5.6 and ISO 1600). e Response time of the BECD measured during cyclic on/off states (–1.2 V/ 1 V). The left dashed line region is bleaching time (t_b = 20.5 s) and right dashed line region is coloration time (t_c = 21.7 s). f Sequential images of degradation of the BECD on a soil with radish seeds planted and sprinkled water every day for 21 days at room temperature (Aperture F 5.6 and ISO 6400).