Highly-conductive porous poly(ether ether ketone) electrolyte membranes for flexible electrochromic devices with variable infrared emittance

A Flexible Long-Wave Infrared Radiation Modulator Integrated with Electrochromic Behavior for Dual-Band Camouflage

Electrochromic devices (ECDs), which are capable of modulating optical properties in the visible and long-wave infrared (LWIR) spectra under applied voltage, are of great significance for military camouflage. However, there are a few materials that can modulate dual frequency bands. In addition, the complex and specialized structural design of dual-band ECDs poses significant challenges. Here, we propose a novel approach for a bendable ECD capable of modulating LWIR radiation and displaying multiple colors. Notably, it eliminates the need for a porous electrode or a grid electrode, thereby improving both the response speed and fabrication feasibility. The device employs multiwalled carbon nanotubes (MWCNTs) as both the transparent electrode and the LWIR modulator, polyaniline (PANI) as the electrochromic layer, and ionic liquids (HMIM[TFSI]) as the electrolyte. The ECD is able to reduce its infrared emissivity (Δε = 0.23) in a short time (resulting in a drop in infrared temperature from 50 to 44 °C) within a mere duration of 0.78 ± 0.07 s while changing its color from green to yellow within 3 s when a positive voltage of 4 V is applied. In addition, it exhibits excellent flexibility, even under bending conditions. This simplified structure provides opportunities for applications such as wearable adaptive camouflage and multispectral displays.

Cobweb-Inspired Quintuple Network Structures toward High-Performance Wearable Electrochromic Devices with Excellent Bending Resistance

Flexible electrochromic devices (FECDs) have been regarded as an ideal stratagem for wearable displays. However, it remains a great challenge to achieve long-term stability for high-performance FECDs due to their severe electrolyte deformation/leakage under repeated bending. Herein, inspired by the rough and fluffy microstructure of cobwebs, we prepared a porous polylactic acid (PLA) network through electrospinning and nonsolvent-induced phase separation. This loosely interlaced PLA network can be well infiltrated by electrolytes and exhibits extraordinarily high transparency; in addition, its surface contains numerous tiny holes to effectively load electrolytes to mitigate deformation. Furthermore, we also introduced silver nanowires (AgNWs) as the supporting network to load and connect electrochromic materials. After assembling them with graphene (GR) electrodes, a wearable FECD with a quintuple network structure (two GR networks, two AgNW networks, and one PLA network) was successfully prepared. The resulting FECD can realize high optical modulation (more than 70%), excellent cyclic stability (retain 95% after 1000 cycles), and innovative bending resistance (retain 84.8% after 6000 bending cycles). This work not only solves the long-lasting challenge of developing FECD with high optical modulation and bending resistances but also provides an energetic paradigm for diverse soft electronics used in harsh environments.

Bioinspired Microstructured Materials for Optical and Thermal Regulation

Precise optical and thermal regulatory systems are found in nature, specifically in the microstructures on organisms' surfaces. In fact, the interaction between light and matter through these microstructures is of great significance to the evolution and survival of organisms. Furthermore, the optical regulation by these biological microstructures is engineered owing to natural selection. Herein, the role that microstructures play in enhancing optical performance or creating new optical properties in nature is summarized, with a focus on the regulation mechanisms of the solar and infrared spectra emanating from the microstructures and their role in the field of thermal radiation. The causes of the unique optical phenomena are discussed, focusing on prevailing characteristics such as high absorption, high transmission, adjustable reflection, adjustable absorption, and dynamic infrared radiative design. On this basis, the comprehensive control performance of light and heat integrated by this bioinspired microstructure is introduced in detail and a solution strategy for the development of low-energy, environmentally friendly, intelligent thermal control instruments is discussed. In order to develop such an instrument, a microstructural design foundation is provided.

Inorganic all-solid-state electrochromic devices with reversible color change between yellow-green and emerald green

All-solid-state electrochromic devices with the structure of glass/ITO/WO₃/Ta₂O₅/Li/V₂O₅/ITO were prepared by an evaporation method. Because of the use of a V₂O₅ complementary layer, the ECD can achieve obvious color change between yellow-green and emerald green with superior cycling performance up to 5000 cycles, indicating the great potential in smart window applications.