Despite the remarkable progress in the development of sweat sensors, self-powered sweat-responsive sensing displays that detect sweat in electric signals with simultaneous and direct visualization of the sweat is rarely demonstrated. Here, a self-powered sweat-responsive structural color (SC) display enabled by ionomer-doped block copolymer (BCP) photonic crystals (PCs) is presented. The sweat-responsive BCP PC is developed by employing a cross-linking single-mobile ionomer (SMI) with mobile anions anchored to immobile polycations to a 1-D BCP PC. The hydrophobic SMI-doped BCP PC is mechanically robust as well as water and temperature-resistive, exhibiting ionomer concentration-dependent full visible SCs. Moreover, the mobile anions periodically confined in the SMI-doped BCP PC harvest triboelectric energy, giving rise to a high-power density of approximate to 0.774 Mw cm-2. Cation-sensitive SC variation is observed in the SMI-doped BCP PC, allowing the visualization of sweat containing various cations. A skin-patchable self-powered sweat-responsive display is demonstrated in which kirigami-patterned SMI-doped BCP PC incorporated in the display can withstand up to 50% strain during exercise. Sweat from the exercise is visualized via SC display and measured using both ionic resistance changes and triboelectric signals. In addition, the integration of sweat sensing membrane into SMI-doped BCP PC enables the quantification of sweat. A self-powered sweat-responsive sensing display enabling ionic as well as triboelectric detection of sweat with its simultaneous and direct structural color visualization is demonstrated, based on sweat-responsive block copolymer photonic crystals doped with single-mobile ionomer. Furthermore, by employing cation-selective membranes to the sensing display, the sweat is quantified in addition to the visualization of sweat. image

Optical encryption using coloration and photoluminescent (PL) materials can provide highly secure data protection with direct and intuitive identification of encrypted information. Encryption capable of independently controlling wavelength-tunable coloration as well as variable light intensity PL is not adequately demonstrated yet. Herein, a rewritable PL and structural color (SC) display suitable for dual-responsive optical encryption developed with a stimuli-responsive SC of a block copolymer (BCP) photonic crystal (PC) with alternating in-plane lamellae, of which a variety of 3D and 2D perovskite nanocrystals is preferentially self-assembled with characteristic PL, is presented. The SC of a BCP PC is controlled in the visible range with different perovskite precursor doping times. The perovskite nanocrystals developed in the BCP PC are highly luminescent, with a PL quantum yield of ≈33.7%, yielding environmentally stable SC and PL dual-mode displays. The independently programmed SC and PL information is erasable and rewritable. Dual-responsive optical encryption is demonstrated, in which true Morse code information is deciphered only when the information encoded by SCs is properly combined with PL information. Numerous combinations of SC and PL realize high security level of data anticounterfeiting. This dual-mode encryption display offers novel optical encryption with high information security and anti-counterfeiting.

Optical encryption technologies based on room-temperature light-emitting materials are of considerable interest. Herein, we present three-dimensional (3D) printable dual-light-emitting materials for high-performance optical pattern encryption. These are based on fluorescent perovskite nanocrystals (NCs) embedded in metal-organic frameworks (MOFs) designed for phosphorescent host-guest interactions. Notably, perovskite-containing MOFs emit a highly efficient blue phosphorescence, and perovskite NCs embedded in the MOFs emit characteristic green or red fluorescence under ultraviolet (UV) irradiation. Such dual-light-emitting MOFs with independent fluorescence and phosphorescence emissions are employed in pochoir pattern encryption, wherein actual information with transient phosphorescence is efficiently concealed behind fake information with fluorescence under UV exposure. Moreover, a 3D cubic skeleton is developed with the dual-light-emitting MOF powder dispersed in 3D-printable polymer filaments for 3D dual-pattern encryption. This article outlines a universal principle for developing MOF-based room-temperature multi-light-emitting materials and a strategy for multidimensional information encryption with enhanced capacity and security.

Dual-mode optical encryption based on holographic metasurfaces and color components is of great attraction because of their enhanced information security and storage; however, the realization of independently as well as reversibly encodable holographic metasurfaces and color components remains unreported. Herein, we present reconfigurable dual-mode encryptions of structural colors (SC) and holograms, achieved through stimuli-responsive block copolymer (BCP) photonic crystals (PCs) with micro-imprinted holographic metasurfaces. Holographic images appear when the micro-imprinted BCP PCs, consisting of self-assembled alternating lamellae of two dielectrics, are exposed to an incident laser. A characteristic SC develops in the visible range when the imprinted film is immersed in a liquid agent that can swell one of the dielectrics, allowing for dual-mode holographic and SC encodings in the solid and liquid states, respectively. The dual-mode optical encoding is reconfigured. The holographic image can be erased and replaced with another micropattern, while preserving the SC. Moreover, an SC, set by crosslinking of the swellable lamellae, is reset by chemical de-crosslinking and subsequent transient re-crosslinking, enabling the SC reconfigurability of the BCP PC film. A prototype of a high-security reconfigurable dual encryption has been developed, wherein true information is decrypted when holographic passwords are confirmed with full-color visible SC passwords.

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 electric‐switching (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 and mechanical integrity properties of OH. Additionally, the topologically micropatterned BCP PC allows lateral diffusion of ionic salts through the sides of the patterned domain under E‐field, facilitating E‐switching speeds of ≈30 s.