RESUMO
A high-level infrared dynamic patterned encoder (IR-DPE) possesses prospective applications for energy-harvesting and information, but a simple and reliable method for fabrication remains challenging. Herein, we first report an IR-DPE with multiple thermal radiation characteristics based on polyaniline (PANI). Specifically, the electron-beam evaporation technique is introduced to obtain the divanadium pentoxide (V2O5) coating, and then the V2O5 film acts as an oxidant to drive in situ polymerization of the PANI film. During the process, we experimentally explore the relationship between the thickness of V2O5 and the emissivity of PANI to obtain up to six emissivity levels and achieve the IR pattern integrated into multiple thermal radiation characteristics. The device shows multiple thermal radiation characteristics at the oxidized state, realizing a pattern visible with the IR camera and the same thermal radiation properties at the reduced state, leading to the pattern concealed in the IR regime. In addition, the highest emissivity tunability of the device is to be tuned from 0.40 to 0.82 (Δε = 0.42) at 2.5-25 µm. Meanwhile, the device exhibits a maximum temperature control of up to 5.9 °C. The results show the enormous potential of IR-DPEs for IR information transfer and thermal management.
RESUMO
A multifunctional electronic skin with thermal radiation regulation and electromagnetic interference (EMI) shielding is urgent for electronic systems because of the thermal radiation emission and electromagnetic wave pollution. Herein, a flexible electronic skin was designed and fabricated, where the polyaniline (PANI) served as the functional layer and Ti3C2Tx MXene was employed as the conductive electrode. The transformation of emeraldine salt (ES) and leucoemeraldine base (LB) of PANI makes the skin achieve an infrared emissivity modulation, and the electromagnetic loss of PANI and ultrahigh electrical conductivity of Ti3C2Tx MXene make it exhibit EMI shielding ability. Benefiting from the special structural design, the multifunctional skin with a small thickness (0.3 mm) and low surface density (0.06 g/cm2) exhibits an excellent infrared emissivity modulation ability (Δε) of 0.32 with emissive power of 119.1 W/m2 at the wavelength range of 2.5-25 µm and total shielding effectiveness (SET) of 36.3 dB over the X-band (8.2-12.4 GHz). Meanwhile, the multifunctional skin remains black in the visible spectrum but a changeable color in the infrared spectrum. Even after repeated bending and twisting, the multifunctional skin still maintains a good emissivity adjustment. The simultaneous realization of dynamic thermal radiation regulation and EMI shielding endows the skin promising potential for various fields, such as adaptive infrared camouflage, thermal regulation, anticounterfeiting, and EMI shielding-related crossing field.
RESUMO
Thermal radiation in the mid-infrared region profoundly affects human lives in various fields, including thermal management, imaging, sensing, camouflage, and thermography. Due to their fixed emissivities, radiance features of conventional materials are usually proportional to the quadruplicate of surface temperature, which set the limit, that one type of material can only present a single thermal function. Therefore, it is necessary and urgent to design materials for dynamic thermal radiation regulations to fulfill the demands of the age of intelligent machines. Recently, the ability of some smart materials to dynamically regulate thermal radiation has been evaluated. These materials are found to be competent enough for various commands, thereby, providing better alternatives and tremendously promoting the commercial potentials. In this review, the dynamic regulatory mechanisms and recent progress in the evaluation of these smart materials are summarized, including thermochromic materials, electrochromic materials, mechanically and humidity responsive materials, with the potential applications, insufficient problems, and possible strategies highlighted.