Electrochemical Actuators with Multicolor Changes and Multidirectional Actuation

Abstract

developed to achieve dual-responsive devices with color change and actuation, such as thermoelectric actuators, magnetochromic actuators, and photochromic actuators, to facilitate their application in military camouflage, robotics, healthcare, etc. [3][4][5][6] However, the stimulus sources of dual-responsive devices are affected by the surrounding environmental conditions, thereby hindering the development of highly controllable and precise dualresponsive behaviors.Compared with the stimuli mentioned above, electricity is highly controllable and hence provides a potential pathway for achieving high-frequency, stable, and accurate dual-responsive devices. [7][8][9] Among various electricity-induced strategies, the electrochemical (EC) method has garnered significant attention owing to its low driving voltage and large actuation amplitude, and is generally classified into two categories: a method based on electric dual-layer capacitance (EDLC) and one based on pseudocapacitance. [10][11][12] In the EDLC-based method, the surface electro-sorption/-desorption of electrolyte ions will cause reversible expansion and recovery of micro-/nanopores, thereby inducing reversible actuation. [13][14][15] However, it is difficult to simultaneously trigger optical color changes (bandgap structure) for the EDCL process based on only the adsorption and the desorption of ions.Pseudocapacitive EC actuators primarily rely on the Faradic redox reaction and involve ion intercalation into the active materials to achieve volumetric expansion and contraction. [10,[16][17][18][19] Hence, it is particularly important to introduce changes in the optical bandgap based on the EC actuator to achieve the dual-responsive of color/shape changes. For instance, Detsi et al. coated a nanolayer of electrochromic polymer onto the ligaments of nanoporous gold, which caused reversible dimensional and color changes during EC actuation. [20] Our team fabricated an electrochromic actuator based on W 18 O 49 nanowires (W 18 O 49 NWs) and demonstrated the color change/actuation dual-responsive phenomenon. [21] Macroscopic actuation was systemically investigated and derived from the lattice contraction/recovery of W 18 O 49 NWs during Li ion (Li + ) de-/intercalation. Nevertheless, a few challenges remain to be addressed. 1) The dual-responsive actuators in the air cannot present the color changes, owing to the inconspicuous color contrast Electrochemical (EC) actuators have garnered significant attention in recent years, yet there are still some critical challenges to limit their application range, such as responsive time, multifunctionality, and actuating direction. Herein, an EC actuator with a back-to-back structure is fabricated by stacking two membranes with bilayer V 2 O 5 nanowires/single-walled carbon nanotubes (V 2 O 5 NWs/SWCNTs) networks, and shows a synchronous high actuation amplitude (about ±9.7 mm, ±28.4°) and multiple color changes. In this backto-back structure, the inactive SWCNTs layer is used as a conductive current collector, and the bil...

Ultrafast, Stable Electrochromics Enabled by Hierarchical Assembly of V2O5@C Microrod Network

“…In the Raman spectra, peaks at 284, 304, 406, and 995 cm −1 can be clearly observed, which corresponds to the bending vibration of O C −V−O B , bending vibration of V−O C , tensible vibration of V−O B −V, and vibrations of the V�O bond, respectively. 32,33 The peak at 143 cm −1 is attributed to the characteristic lattice bending vibration of V 2 O 5 , 34 indicating the successful conversion to V 2 O 5 . As shown in XPS spectra of V 2 O 5 @C microrods (Figures S5a and S5b in the Supporting Information), C 1s peak was observed at 288.1 eV, and the carbon content was calculated to be ca.…”

“…The vis-NIR transmittance spectra show that it exhibits a certain adjustment ability in the NIR region (Figure S11 in the Supporting Information). In situ Raman spectrum (Figure S12 in the Supporting Information) of EC electrode was tested to elaborate the redox process of V 2 O 5 @C, when a negative voltage was applied to the EC electrode, the Raman peaks at 284 (v 1 ), 304 (v 2 ), and 406 (v 3 ) cm –1 were gradually weakened when Li + inserted into the interlayer spaces of V 2 O 5 , indicating the lengthening of O C –V–O B bond, V–O C bond, V–O B –V and phase transformations of V 2 O 5 . After the +1 V voltage was applied, peak intensity recovered due to the extraction of Li + from the V 2 O 5 @C EC layer.…”

Wearable electrochromic materials and devices: from visible to infrared modulation

“…Inspired by the dual-responsive behaviour of octopuses, our group designed a dual-responsive composite film by attaching a bilayer 1D network composed of V 2 O 5 nanowires (V 2 O 5 NWs) and SWCNTs on a porous polymer membrane to extend the dual-responsive mode. 140 The composite film demonstrated synchronous colour changes (optical reflectance variation at 550 nm from 40.5% to 12.7%) and actuation (bending angle of 1731). Two composite films were stacked to assemble the air-working EC actuators, which showed colour changes between yellow and greyish green and a high actuation distance (about AE9.7 mm, AE28.41) between AE1.8 V bias (Fig.…”

Stretchable, Electrochemically‐Stable Electrochromic Devices Based on Semi‐Embedded Ag@Au Nanowire Network

“…Flexible electrochromic (EC) devices with high controllability, fast switching speed, and low power consumption have attracted significant attention, [1][2][3][4][5] and show broad applications in wearable electronics and smart clothing, including display, dynamic camouflage, and visual sensation. [6][7][8][9][10][11] Considering that the the reduced graphene oxide (rGO)-coated Ag NW films exhibited highly enhanced thermal oxidation and chemical stabilities due to the excellent gas-barrier property of the rGO layer. [40] Despite these achievements, the coated Ag NWs cannot withstand harsh mechanical stretchability and electrochemical reaction environment due to inelastic structure, weak adhesion to substrates, and incomplete coverage and protection on Ag NWs.…”

“…Flexible electrochromic (EC) devices with high controllability, fast switching speed, and low power consumption have attracted significant attention, [ 1–5 ] and show broad applications in wearable electronics and smart clothing, including display, dynamic camouflage, and visual sensation. [ 6–11 ] Considering that the motion of human joints will cause large tensile deformation, the EC devices with stretchability are highly desired to adapt the irregular and dynamic surfaces. [ 12–14 ] Unfortunately, related reports are limited due to the complex device structure and electrochemical redox mechanism.…”