High Breakthrough Pressure in Hydrogels Enabled Ultrastable Treatment of Hypersaline Wastewaters.

Surface effects of low-surface-tension contaminants accumulating at the evaporation surface easily induce wetting in membrane distillation, especially in hypersaline scenarios. Herein, we propose a novel strategy to eliminate the surface effect and redistribute contaminants at the evaporation interface simply by incorporating a layer of hydrogel. The as-fabricated composite membrane exhibits remarkable stability, even when exposed to solution with salt concentration of 5 M and surfactant concentration of 8 mM. Breakthrough pressure of the membrane reaches 20 bar in the presence of surfactants, surpassing commercial hydrophobic membranes by one to two magnitudes. Density functional theory and molecular dynamics simulations reveal the important role of the hydrogel-surfactant interaction in suppressing the surface effect. As a proof of concept, we demonstrate the membrane in stably processing synthetic wastewater containing 144 mg L-1 surfactants, 1 g L-1 mineral oils, and 192 g L-1 NaCl, showing its potential in addressing challenges of hypersaline water treatment.

Enhanced Moisture Condensation on Hierarchical Structured Superhydrophobic-Hydrophilic Patterned Surfaces.

Patterned surfaces combining hydrophobic and hydrophilic properties show great promise in moisture condensation; however, a comprehensive understanding of the multiscale interfacial behavior and the further controlling method is still lacking. In this paper, we studied the moisture condensation on a hybrid superhydrophobic-hydrophilic surface with hierarchical structures from micro- to nanoscale. For the first time, we demonstrated the effects of wettability difference and microstructure size on the final condensation efficiency. By optimizing the wettability difference, sub-millimeter pattern width, and microstructure size, maximum 90% enhancement of the condensation rate was achieved as compared with the superhydrophobic surface at a subcooling of 13 K. We also demonstrated the enhanced condensation mechanism by a detailed analysis of the condensation process. Our work proposed effective and systematical methods for controlling and optimizing moisture condensation on the patterned surfaces and shed light on application integration of such promising functional surfaces.

Understanding capacity fading of the LiVO3 cathode material by limiting the cutoff voltage.

The effects of discharge cutoff voltages on the structural evolution and electrochemical performance of the LiVO3 cathode upon cycling are investigated by electrochemical measurements, electrochemical impedance spectroscopy, ex situ X-ray diffraction, Raman spectra, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. It is found that a lower cutoff voltage causes formation and accumulation of unstable V4+ ions on the surface of the electrode, which easily leads to severe structural deterioration and capacity fading. A limited cutoff voltage between 3.5 and 1.5 V can effectively enhance the structural stability and consequently the electrode demonstrates 75.9% capacity retention and neglectable working voltage decay over 400 cycles. The result that the operation voltage range strongly affects the structural stability of cycled LiVO3 provides a new insight into exploring feasible approaches to achieve highly stable LiVO3 and other vanadium-based electrodes for lithium-ion batteries.

Stretchable and Self-Powered Temperature-Pressure Dual Sensing Ionic Skins Based on Thermogalvanic Hydrogels.

Tactile sensors with both temperature- and pressure-responsive capabilities are critical to enabling future smart artificial intelligence. These sensors can mimic haptic functions of human skin and inevitably suffer from tensile deformation during operation. However, almost all actual multifunctional tactile sensors are either nonstretchable or the sensing signals interfere with each other when stretched. Herein, we propose a stretchable and self-powered temperature-pressure dual functional sensor based on thermogalvanic hydrogels. The sensor operates properly under stretching, which relies on the thermogalvanic effect and constant elastic modulus of hydrogels. The thermogalvanic hydrogel elastomer exhibits an equivalent Seebeck coefficient of -1.21 mV K-1 and a pressure sensitivity of 0.056 kPa-1. Combined with unit array integration, the multifunctional sensor can be used for accurately recording tactile information on human skin and spatial perception. This work provides a conceptual framework and systematic design for stretchable artificial skin, interactive wearables, and smart robots.