Tortuosity Engineering of Water Channels to Customized Water Supply for Enhancing Hydrogel Solar Evaporation.

Hydrogel as a solar evaporator shows great potential in freshwater production. However, hydrogels often lead to an imbalance between solar energy input and water supply management due to their excessively high saturated water content. Thus, achieving a stable water-energy-balance in hydrogel evaporators remains challenging. Here, by tortuosity engineering designed water transport channels, a seamless high-tortuosity/low-tortuosity/high-tortuosity structured hydrogel (SHLH structure hydrogel) evaporator is developed, which enables the hydrogel with customized water transport rate, leading to the controlled water supply at the evaporator interface. An excellent equilibrium between the photothermal conversion and water supply is established, and the maximum utilization of solar energy is realized, thereby achieving an excellent evaporation rate of 3.64 kg m-2 h-1 under one solar illumination. This tortuosity engineering controlled SHLH structured evaporator provides a novel strategy to attain water-energy-balance and expands new approaches for constructing hydrogel-based evaporators with tailored water transportation capacity.

Pose error correction in offline three-dimensional profile measurement system for large-diameter aspheric mirror.

This paper proposes an offline measurement method for a large aspheric mirror during its grinding stage. A measurement method and mathematical model to realize a three-dimensional (3D) profile measurement for large-diameter aspheric mirrors are proposed, based on a cylindrical coordinate system. The measurement error induced by the alignment error is examined based on the error analysis of the measurement and workpiece coordinate systems. The corresponding pose error obtained through the nonlinear least squares method is eliminated to improve the measurement accuracy. To evaluate the entire surface profile error, a 3D profile model is established. The total uncertainties of the proposed measurement system are also estimated. Comparison experiments for a 300-mm-diameter K9 glass workpiece are conducted on UPFM900 and Taylor Hobson PGI 3D profile instruments, and the profile accuracy is found to be improved from 15.3 to 7.12 µm after eccentricity and tilt error elimination.

Alignment Method for Linear-Scale Projection Lithography Based on CCD Image Analysis.

This paper presents a method to improve the alignment accuracy of a mask in linear scale projection lithography, in which the adjacent pixel gray square variance method is applied to a charge-coupled device (CCD) image to obtain the best position of the focal length of the motherboard and then realize the alignment of the focal plane. Two image positions in the focal plane of the CCD are compared with the traits overlap according to the image splicing principle, and four typical errors are corrected on the basis of the total grating errors. Simultaneously, the rotation error of the mask is used to summarize the grayscale variation function of the CCD image. Threshold functions are employed to express the factors including the wave crests of the amplitude, period error, and phase error, which govern the rotation accuracy and weight alignment accuracy expression of the established four error factors. Finally, in the experiment, the slope of the mask is corrected and adjusted to the same direction as the slide plate with the assistance of a dual-frequency laser interferometer. The effect of the alignment error on the lithography accuracy is discussed and verified in the static case, and it is found that the CCD maximum resolution pixel is 0.1 µm and accuracy of the scale is 0.79 µm in only a 200-mm-measurement range.

Enabling Self-Adaptive Water-Energy-Balance of Photothermal Water Diode Evaporator: Dynamically Maximizing Energy Utilization Under the Ever-Changing Sunlight.

Maintaining a match between input solar energy and required energy by water supply management is key to achieving efficient interfacial solar-driven evaporation (ISDE). In practice, the solar radiation flux is constantly changing throughout the day, so keeping a dynamic water-energy-balance of ISDE is a big challenge. Herein, a photothermal water diode (WD) evaporator concept is proposed by an integrated hydrophilic/hydrophobic Janus absorber to overcome the issue. Due to the unique unidirectional water transport properties induced by asymmetric wettability, a self-adaptive balance between photothermal energy input and water uptake is established, thus realizing the energy matching and utilization maximization. The experimental and simulation results exhibit that with the increase of sunlight intensity, the water supply speed is significantly accelerated due to the dynamic management and self-regulation on water replenishment. Therefore, an excellent evaporation rate of up to 2.14 kg m-2 h-1 with a high efficiency of 93.7% under 1 sun illumination is achieved. This water diode engineering with Janus wettability provides a novel strategy and extends the path for designing solar evaporation systems with diverse water supply properties, which shows great potential in different environmental conditions.

Superhydrophilic Interconnected Biomass-Based Absorbers Toward High-Speed Evaporation for Solar Steam Generation.

Taking abundant and sustainable solar energy as the only energy source, solar-powered interface evaporation has been regarded as a promising method to alleviate the pressure of freshwater shortage. However, the uptake of clean water from brine is constantly accompanied by evaporation of water and condensation of vapor, which inevitably generates salt solid, preventing further continuous and stable evaporation. The most direct method is to fabricate a photothermal material with salt self-resistance by using the reflux of salt ions. Here, a superhydrophilic interconnected biomass carbon absorber (SBCA) is prepared by freeze-drying and carbonization, realizing strong liquid pumping, and self-blocking salt. In combination with superior broadband light absorption (94.91%), high porosity (95.9%), superhydrophilicity, and excellent thermal localization, an evaporation device with excellent evaporation rate (2.45 kg m-2 h-1 under 1 kW m-2) is successfully proposed. In the meantime, the porous skeleton and rapid water transport can enhance the diffusion of salt ions and slow down the rate of salt deposition. As a result, no salt deposition is found on the SBCA surface after continuous irradiation at 1 kW m-2 for 15 h. The design can provide a convenient and low-cost efficient strategy for solar steam generators to address clean water acquisition.