High-power laser systems require thin films with extremely low absorption. Ultra-low-absorption films are often fabricated via ion beam sputtering, which is costly and slow. This study analyzes the impact of doping titanium and annealing on the absorption characteristics of thin films, focusing on composition and structure. The results indicate that the primary factor influencing absorption is composition. Suppressing the presence of electrons or holes that do not form stable chemical bonds can significantly reduce absorption; for amorphous thin films, the structural influence on absorption is relatively minor. Thus, composition control is crucial for fabricating ultra-low-absorption films, while the deposition method is secondary. Ion beam-assisted electron-beam evaporation, which is relatively seldom used for fabricating low-absorption films, was employed to produce high-reflectivity films. After annealing, the absorption at 1064 nm reached 1.70 parts per million. This method offers a cost-effective and rapid approach for fabricating ultra-low-absorption films.

Passive radiation cooling technology, as a new zero-energy refrigeration technology method, has received widespread attention in recent years. However, due to differences in the testing devices used by different teams, it becomes difficult to directly compare the cooling performance of the respective prepared materials. This study combines experimental and theoretical methods to explore the impact of testing equipment and sample size on the results of the radiative cooling capacity evaluation. The research results show that when evaluating the cooling performance of materials in thermal insulation chambers, if the sample diameter is equal to or larger than 10 cm, at a sample diameter ≥ 10 cm in insulated chambers, cooling capacity stabilizes at ~25 °C (daytime) and ~28 °C (nighttime), with <2% variation across larger sizes. The evaluation of cooling capacity is not affected by the structure of the test equipment or the size of the material. However, variations in sample placement depth will always have a significant impact on the evaluation results, so a uniform placement depth needs to be specified. In addition, when using an open device to evaluate the cooling performance of materials, if the sample diameter is greater than or equal to 10 cm and the foam pad thickness is greater than or equal to 8 cm, foam pad thickness ≥ 8 cm in open devices reduces thermal interference by 89%, enabling consistent evaluations. The measured value of the cooling capacity is also not affected by the structure and material size of the test device. This study provides a basis for the standardization of radiant cooling testing, thereby promoting the practical application of radiant cooling technology.

Radiative cooling presents a promising passive cooling strategy, though its widespread adoption is often constrained by elevated costs and manufacturing complexities. This study introduces a cost-effective, scalable fabrication method for a composite membrane utilizing a spraying technique, and it was fabricated by spraying a mixture of modified nano-zirconia and ethylene-octene copolymer (POE), dissolved in petroleum ether, onto a polyethylene (PE) bubble film substrate. This composite membrane demonstrates a hydrophobic property, with a water contact angle of 100.6°. A cooling structure was formed by covering the composite membrane onto a polytetrafluoroethylene (PTFE) plate which served as an emitter, and the cooling power of this structure reaches 66.2 ± 4.3 W/m². Field tests reveal a temperature reduction of 3 ± 0.3 °C at noon and an average cooling effect of 4.7 ± 0.3 °C throughout the day, relative to ambient temperatures. This work advances the development of cost-effective, scalable radiative cooling technologies, holding promise for applications in building cooling and energy efficiency.

Fossil fuel consumption for heating and cooling represents a considerable portion, approximately half, of the world’s total energy use, thereby presenting a substantial challenge in diminishing dependence on these energy sources. Our study presents the design and fabrication of a zero-energy switchable radiative cooler (ZESRC) to address the global climate crisis by reducing energy consumption within buildings. ZESRC utilizes a simple morphology-driven method that exploits materials’ differing thermal expansion coefficients, enabling a seamless switch between cooling and heating modes at any preset temperature point, enabling superior adaptive thermal management. Field experiments demonstrate that, relative to ambient temperature, ZESRC usage results in a maximum temperature decrease of 7.1°C during summer and a maximum increase of 7.5°C in winter. Furthermore, we developed an energy-efficiency map for different climate zones, showing the ZESRC’s superiority over devices with only solar heating or radiative cooling, cutting building energy use by 14.3%. The results underscore the ZESRC’s capability for net-zero energy consumption, significantly advancing global energy conservation and the 2050 net-zero carbon goal.

Humidity monitoring is essential in industrial and scientific scenarios, yet remains challenging for compact EMI (electromagnetic interference)-immune sensors with high sensitivity and robust stability. A novel fiber Bragg grating (FBG) humidity sensor was developed, which incorporated LiCl@UIO-66 microfillers within a poly(N-isopropylacrylamide) (PNIPAM) hydrogel matrix. Structural characterization using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and Fourier-transform infrared (FTIR) spectroscopy confirms that LiCl is confined or nanodispersed within intact UIO-66, and that interfacial ion–dipole/hydrogen-bonding exists between the composite and water. Systematic variation in coating time (30–720 min) reveals monotonic growth of the total wavelength shift with diminishing returns. A coating time of 4 h was found to yield a wavelength shift of approximately 0.38–0.40 nm, representing about 82% of the maximum shift observed at 12 h, while maintaining good quasi-linearity and favorable kinetics. Calibration demonstrates sensitivities of 6.7 pm/%RH for LiCl@UIO-66_33 and 10.6 pm/%RH for LiCl@UIO-66_51 over ~0–95%RH. Stepwise tests show response times t90 of ≈14 min for both composites, versus ≈30 min for UIO-66 and ≈55 min for neat PNIPAM. Long-term measurements on the 51 wt.% device are stable over the first ~20 days, with only slow drift thereafter, and repeated humidity cycling is reversible. The wavelength decreases monotonically during drying while settling time increases toward low RH. The synergy of hydrogel–MOF–salt underpins high sensitivity, accelerated transport, and practical stability, offering a scalable route to high-performance optical humidity sensing.