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Abstract Moisture-driven electricity generators (MEGs) have been extensively researched; however, high-performance flexible variants have seldom been demonstrated. Here we present a novel complex coacervation with built-in potential strategy for developing a high-performance uniaxial MEG, featuring a core of poly(3,4-ethylenedioxythiophene) (PEDOT) with a built-in charge potential and a gel shell composed of poly(diallyldimethylammonium chloride) (PDDA) and sodium alginate (NaAlg) coacervate. The complex coacervation of two oppositely charged polyelectrolytes produces extra mobile carriers and free volume in the device; meanwhile, the PEDOT core’s surface charge significantly accelerates carrier diffusion. Consequently, the uniaxial fiber-based MEG demonstrates breakthrough performance, achieving an output voltage of up to 0.8 V, a maximum current density of 1.05 mA/cm2, and a power density of 184 μW/cm2 at 20% relative humidity. Moreover, the mechanical robustness is ensured for the PEDOT nanoribbon substrate without performance degradation even after 100,000 folding cycles, making it suitable for self-powered human interactive sensor and synapse. Notably, we have constructed the inaugural MEG-synapse self-powered device, with a fiber-based MEG successfully operating a synaptic memristor, thereby emulating autonomous human synapses linked with fibrous neurons. Overall, this work pioneers innovative design strategies and application scenarios for high-performance MEGs.

Abstract 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.

Soft actuators that can operate at high temperatures are of great interest in emerging research fields such as microfluidics, soft robotics, automotive, aircraft, and bioelectronics. However, most polymer-based flexible actuators suffer from performance degradation at elevated temperatures above 60 °C. In this paper, we present the high-temperature electromechanical actuation of relaxor ferroelectric polymers solution-blended with normal ferroelectric polymers. We conduct a systematic analysis of the electromechanical properties of three unimorph actuators with relaxor ferroelectric poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene)s [P(VDF-TrFE-CFE)s] containing different amounts of chlorofluoroethylene (CFE) moieties (approximately 1, 3.5, and 9 wt%). In this study, we propose the film stress, given as Young's modulus times strain, as the measure of the electromechanical performance of soft bending actuators under loading, rather than strain or strain energy density. We demonstrate that a relaxor ferroelectric actuator with 1-wt% CFE, which mixes high-modulus ferroelectric crystal domains with an optimized electrostrictive relaxor phase, develops a high film stress of ∼3.5 MPa. When blended with the normal ferroelectric P(VDF-TrFE), the actuator exhibits excellent film stress of approximately 3.1 MPa at an elevated temperature of 60 °C comparable with that at 25 °C. The high-modulus ferroelectric crystals in P(VDF-TrFE) reinforce the mechanical properties of the actuator at elevated temperatures, generating high-temperature electromechanical actuation with a large strain and strain energy density of approximately 1.6% and 23 mJ/cm², respectively. We also demonstrate successful microfluidic pump operation at 60°C with our actuator using a relaxor ferroelectric polymer blended with an intrinsic ferroelectric polymer.

Abstract In this study, we present a promising and facile approach toward the fabrication of non-toxic, water-stable, and eco-friendly luminescent fiber paper composed of polycaprolactone (PCL) polymer and CsPbBr3@SiO2 core–shell perovskite nanocrystals. PCL-perovskite fiber paper was fabricated using a conventional electrospinning process. Transmission electron microscopy (TEM) clearly revealed incorporation of CsPbBr3@SiO2 nanocrystals in the fibers, while scanning electron microscopy (SEM) demonstrated that incorporation of CsPbBr3@SiO2 nanocrystals did not affect the surface and diameter of the PCL-perovskite fibers. In addition, thermogravimetric analysis (TGA) and contact angle measurements have demonstrated that the PCL-perovskite fibers exhibit excellent thermal and water stability. The fabricated PCL-perovskite fiber paper exhibited a bright green emission centered at 520 nm upon excitation by ultra-violet (UV) light (374 nm). We have demonstrated that fluorescent PCL-perovskite fiber paper is a promising candidate for anti-counterfeiting applications because various patterns can be printed on the paper, which only become visible after exposure to UV light at 365 nm. Cell proliferation tests revealed that the PCL-perovskite fibers are cytocompatibility. Consequently, they may be suitable for biocompatible anti-counterfeiting. The present study reveals that PCL-perovskite fibers may pave way toward next generation biomedical probe and anti-counterfeiting applications. Graphical Abstract

ABSTRACT For changing environmental circumstances, interactive structural color (SC) observation is a promising strategy to store and express external information. SCs based on self-assembled block copolymer (BCP) photonic crystals have been a research focus due to their facile and diverse nanostructures relying on the volume ratio of blocks. Their unique nano-architectonics can reflect incident light due to constructive interference of the two different dielectric constituents. Their excellent ability to change nano-architectonics in response to external stimuli (i.e. humidity, temperature, pH, and mechanical force) allows for a programmable and stimuli-interactive BCP SC display. In this review, recent advances in programmable and stimuli-interactive SC displays with the 1-dimensional self-assembled BCP nano-architectonics are comprehensively discussed. First, this review focuses on the development of programmable BCP SCs that can store various information. Second, stimuli-interactive BCP SCs capable of responding reversibly to external stimuli are also addressed. Particularly, reversible BCP SC changes are suitable for rewritable displays and emerging human-interactive BCP SC displays that detect various human information through changes in electric signals with the simultaneous alteration of the BCP SCs. Based on previously reported literature, the current challenges in this research field are further discussed, and the perspective for future development is presented in terms of material, nano-architectonics, and process.

Abstract Overcoming the thermal sensitivity of the van‐der Waals layered material, an inevitable high defect concentration in a large area (2 × 2 cm2) vapor phase grown few‐layer MoS2 (2.3 nm thick) is uniformly repaired over the entire area through thermal process. The defect concentration of the healed sample decreased by 3.8 times, and both the PL intensity and field‐effect mobility over the entire area increased by more than two times. Through observing in situ photoluminescence (PL) spectra with raising temperature, it is confirmed that the oxygen‐substitutional healing proceeds radically from the starting point at which trion dissociation energy is zero, inducing e–h plasma. At this time, for achieving successful healing of the entire area, immediate cooling is required to prevent accelerated oxidation when reaching the critical temperature. Considering the laboratory‐dependent crystalline quality of vapor‐phase grown transition metal dichalcogenides (TMDs), the methodology to find the optimal thermal healing temperature through in situ PL monitoring will be quite useful.

Abstract An additive, 1,4‐butadiene sulfone (BDS), which generates H2SO3 by in situ thermal retro‐Diels‐Alder decompositions, is used for preparing high β‐phase polyvinylidene fluoride (PVDF) films. Because of preferential multiple non‐covalent interactions of H2SO3 with all‐trans configuration of PVDF, β‐phase PVDF is spontaneously induced without mechanical drawing and/or extensive thermal annealing process. PVDF films cast from PVDF/BDS/water solutions exhibit high β‐phase content (fβ = 95%) when the BDS concentration is only cBDS = 1.0 wt%, which is confirmed by polarized optical microscopy (POM), SEM, Fourier transform infrared spectroscopy (FT‐IR), differential scan calorimetry (DSC), and 2D grazing incidence wide‐angle X‐ray scattering (GIWAXS). Because of the high β‐phase content, PVDF films prepared by using BDS exhibit excellent ferroelectric and piezoelectric properties (Ec = 50 MV/m, Pr = 5 µC/cm2, and d33 = ≈‐25 pm/V). Furthermore, a triboelectric nanogenerator (TENG) developed with high β‐phase PVDF film exhibits enhanced performance as 2.5 times higher than neat PVDF film in output charge density, allowing reliable operation of conventional electronic devices.

To optimize the electron-hole balance by controlling the electron transport layer in (ETL) in quantum dots light emitting diodes (Q-LEDs), ZnO was modified by doping with Mg and Ga and applied to commercial Q-LEDs as ETLs. By doping ZnO nanoparticles with Ga, the electrons easily inject due to the increased Fermi level of the ZnO nanoparticles. By co-doping with Mg, the valence band maximum of the ZnO nanoparticles deepens and blocks the holes more efficiently. Also at the interface of the QD/ETL, Mg reduces non-radiative recombination by reducing oxygen vacancies on the surface of the ZnO nanoparticles. As a result the maximum luminance and the maximum luminance efficiency of the Q-LEDs increased to 43 440 cd m-2 and 15.4 cd A-1 respectively. These results increased by 34%, 10%, and 27% for the maximum luminance and 450%, 88%, and 208% for maximum luminance efficiency with undoped ZnO and Mg or Ga single doped ZnO ETL. The effect of Mg and Ga co-doping on the maximum luminance and maximum luminescence efficiency will be discussed. [ABSTRACT FROM AUTHOR]

A weak van der Waals (vdW) force in layered materials enables their isolation into thin flakes through mechanical exfoliation while sustaining their intrinsic electronic and optical properties. Here, we introduce a universal roll-printing method capable of producing vdW multilayer films on wafer-to-meter scale. This process uses sequential exfoliation and transfer of layered materials from the powder sources to target substrates through a repeated rolling of a cylindrical metal drum. We achieve uniformly coated films with a library of vdW powders on various mechanically rigid and flexible substrates. The printed films are configured into different devices including light-emitting diodes and photodetectors. The presented technique offers substantial benefits in terms of cost efficiency and a low thermal budget while offering high material quality. [ABSTRACT FROM AUTHOR]