Lattice-contraction triggered synchronous electrochromic actuator.

Li, Kerui; Shao, Yuanlong; Yan, Hongping; Lu, Zhi; Griffith, Kent J; Yan, Jinhui; Wang, Gang; Fan, Hongwei et al. · Nat Commun · 2018

basic_science · Level V

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Abstract

Materials with synchronous capabilities of color change and actuation have prospects for application in biomimetic dual-stealth camouflage and artificial intelligence. However, color/shape dual-responsive devices involve stimuli that are difficult to control such as gas, light or magnetism, and the devices show poor coordination. Here, a flexible composite film with electrochromic/actuating (238° bending angle) dual-responsive phenomena, excellent reversibility, high synchronization, and fast response speed (< 5 s) utilizes a single active component, W<sub>18</sub>O<sub>49</sub> nanowires. From in situ synchrotron X-ray diffraction, first principles calculations/numerical simulations, and a series of control experiments, the actuating mechanism for macroscopic deformation is elucidated as pseudocapacitance-based reversible lattice contraction/recovery of W<sub>18</sub>O<sub>49</sub> nanowires (i.e. nanostructure change at the atomic level) during lithium ion intercalation/de-intercalation. In addition, we demonstrate the W<sub>18</sub>O<sub>49</sub> nanowires in a solid-state ionic polymer-metal composite actuator that operates stably in air with a significant pseudocapacitive actuation.