Low‐Powered E‐Switching Block Copolymer Structural Color Display with Organohydrogel Humidity Controller

Abstract

In particular, PCs based on stimuliadaptive self-assembled colloids, [13][14][15] layer-by-layer, [16,17] and block copolymers (BCPs) [1,4,5,6,[8][9][10][11][12] are suitable for reflectivemode electric-switching (E-switching) SC displays because of their cost-effectiveness, facile development of full-visible color, and mechanical flexibility. The most common E-switching PC devices reported are fabricated into liquid cell-type systems in which various E-field-responsive PCs are embedded in various liquid media (Table S1, Supporting Information). [18][19][20][21][22][23][24][25] The liquid solvent medium employed in E-switching devices maintains a stable dispersion of ordered colloids in colloidal PCs [18][19][20][21] and swells targeted domains in BCP PCs with an E-field. [22][23][24][25] Despite the fast SC switching arising from the rapid kinetics of the solvent, most liquid-cell BCP SC display applications are limited because of their lack of mechanical flexibility and complex fabrication processes required to prevent solvent leakage.Solid-state E-switching PC devices have been developed to resolve this issue (Table S1, Supporting Information). [26][27][28][29] Recently, solid-state E-switching colloidal PC devices were established by encapsulating self-assembled colloidal particles in a polymer matrix. [26][27][28] Dielectric elastomer actuation was implemented in this system, where the external electrical stimulus induces Maxwell stress across the dielectric medium with the PCs. Field-dependent alteration in the periodicities of the colloidal PCs gives rise to E-switching SCs in the full visible range. However, it is unfortunate that such actuation of a few hundred micrometers-thick PC often requires a high E-field of ≈22.5 V µm −1 , [26] corresponding to an operation voltage ranging from 4 to 9 kV. [26][27][28] Only a few Soft-solid photonic crystals (PCs) based on periodically ordered block copolymer (BCP) nanostructures demonstrate stimuli-adaptive structural colors (SCs) and desirable mechanical properties suitable for reflective-mode electricswitching (E-switching) displays. However, the low electrochemical stability and humidity-dependent E-switching performance of hygroscopic ionic salts, often employed for E-field-adaptive structural alteration, limit their applications. In this study, a low-powered capacitive E-switching BCP SC display with an organohydrogel (OH) humidity controller is proposed, where a bilayer of a BCP and a polymer blend with hygroscopic E-field-adaptive ionic salts is sandwiched between Au electrodes. The display reliably exhibits reversible full-color E-switching (100 on/off cycles) at operating voltages of +2.5 to −2 V within the ionic salts' electrochemical window at ≈50% humidity. A patchable and reusable OH serves as a water reservoir (with optimized geometries and dimensions) to improve the display's humidity tolerance, providing a target humidity (≈50%). The proposed display performs at ambient humidity lower than 60% for over 10 days because of the long water retention an...

Interactive structural color displays of nano-architectonic 1-dimensional block copolymer photonic crystals

“…(c) Schematic of E-field programmable BCP SC display where an organohydrogel was placed near a BCP SC of PS- b -QP2VP/PVDF-TrFE-CFE:Li+TFSI − . (d) CIE coordinates of the BCP SC display as a function of humidity conditions from 30 to 50% under +2.5 V. Reproduced with permission [ 50 ]. Copyright 2022, Wiley-VCH.…”

“…The E-field-switching performance of the soft-solid BCP PC SC display was humidity-dependent due to the water associated with Li+ ions in the BCP films [ 50 ]. For example, the initial red BCP SC turned blue with increasing humidity, exhibiting maximum reflections at wavelengths of 451 nm at 90% relative humidity (RH) and 665 nm at 30% RH.…”

“…Further enhancement of SC-switching speed can be made by properly controlling the position and areal density of these screw dislocations. Another way to facilitate SC switching in a BCP SC display is to develop topological micropatterns of the BCP PC films; a swelling agent is laterally diffused into the micropatterns through the side walls of the patterns [ 50 ]. Studies on the SC alteration of micro/nanopatterned BCP PCs with various shapes, symmetries, and dimensions should be performed.…”

“…Since this instrumental work, numerous studies to control the degree of swelling of the domains have been accomplished to manipulate the visible SCs of a BCP not only in liquidous states [ 26–44 ] but also in thin solid films [ 12 , 13 , 45–50 ]. These methods included the addition of salts [ 31–37 ], the control of pH [ 38–41 ], the control of cross-linking of the swollen domains [ 42–44 ], and the manipulation of temperature [ 14 , 47 ], humidity [ 12 , 13 ], pressure [ 15 , 48 ], and external E-field [ 6–11 , 49 , 50 ].…”

Humidity-Tolerant Moisture-Driven Energy Generator with MXene Aerogel–Organohydrogel Bilayer

“…To prepare the organohydrogel, the neat hydrogel was soaked in ethylene glycol for at least 2 h to promote solvent exchange. 41,46 Fabrication of the MAH-MEG. The PAM hydrogel (1 cm 2 ) was placed on the bottom Cu electrode along with the same-sized MXene aerogel, which stuck to the PAM hydrogel.…”