High-Efficient Microdroplet Harvesting and Detaching Inspired from Sarracenia Lid Trichome

True "Liquid Diode": Check Valve@Janus Membrane to Achieve an Extremely High Reverse Breakthrough Pressure

Janus membranes, widely recognized for their remarkable unidirectional permeability, can achieve spontaneous liquid transport from the hydrophobic sides to the hydrophilic sides while impeding liquid flow in the opposite direction. However, the current Janus membrane only possesses limited reverse breakthrough pressure (RBP) (<20 cm water height), which is a key factor in determining the unidirectional liquid transport function. Here, inspired by the one-way blood transport function of heart valves, a solution to the issue above is proposed in the form of a Janus membrane integrated with a gravity-assisted check valve (check valve@Janus membrane). As a result, the breakthrough pressure of the check valve@Janus membrane was observed to be nearly zero in the positive direction. More importantly, the RBP had been observed to reach up to 4 m. This considerable advance in RBP is predominantly attributable to the unparalleled resistance of the check valve to the backward flow. The check valve@Janus membrane results in a perfect unidirectional flow, thereby achieving the concept of a true "liquid diode". This innovation offers a novel method for enhancing the RBP of a Janus membrane, opening up a wealth of potential avenues for future applications in clinical medicine, microfluidics, and other disciplines.

Preparation of Aluminum-Based Dual-Gradient Surfaces for Directional Droplet Transport by Bioinspired Sarracenia Microstructures

Inspired by the ultrafast directional water transport structure of Sarracenia trichomes, hierarchical textured surfaces with specific microgrooves were prepared based on laser processing combined with dip modification, in response to the growing problem of freshwater scarcity. The prepared surfaces were tested for droplet transport behavior to investigate the relationship between the surface structure and the driving force of directional water transport and their effects on the water transport distance and water transport velocity. The results showed that surfaces with a superhydrophobic background associated channels of multirib structures, and a dual-gradient surface of gradient hydrophobic background associated channels with gradient structure performed the best in terms of water transport efficiency. In addition, the water transport process of different samples under Mode II was simulated by CFD, and the dynamic evolution of water film mode formation was obtained to be divided into four phases, including film formation, transition state, mode formation, and stable water transport. This study provides a good reference for the development and preparation of surfaces for directional water transport.

Synergistic Effect of Neighboring Superhydrophilic Patterns on Superhydrophobic Surfaces for Enhanced Fog Collection

In this work, a superhydrophobic surface loaded with elliptical superhydrophilic patterns in a V-shaped arrangement has been fabricated with the help of shape memory membranes with uniform vertically penetrative channels (i.e., SMEUVs, as a mask). The special geometry (elliptical) and arrangement (V-shaped) of superhydrophilic patterns play important roles in the enhancement of fog collection. The former not only facilitates droplet detachment from superhydrophilic regions but also dominates its directional transport. The latter promotes the coalescence of tiny droplets based on directional flow pathway toward collection area, minimizing the risk of re-evaporation of them and providing fresh sites for subsequent nucleation and growth of droplets. The combination of them contributes to the synergistic effect of neighboring superhydrophilic patterns on the superhydrophobic surface. As a result, the optimal specimen (V-shaped arrangement of elliptical superhydrophilic patterns) in this work exhibits much higher fog collection efficiency (∼4 times) relative to the reference (superhydrophobic or superhydrophilic surface). Our results are significant for the design and fabrication of fog collection systems.

A critical review of sodium alginate-based composites in water treatment

The global freshwater crisis is a pressing issue, especially in areas with little rainfall and inner continental regions. The growing attention to water scarcity has induced increased interest in research on advanced water treatment technologies. As an abundant bioactive material in nature, sodium alginate (SA) has been widely used in water management due to its outstanding water absorption and holding ability, reversible swelling property, and pollutant adsorption performance. Building on this, progress made in using various modified forms of SA to access clean water is addressed in this review. Covering studies concern the adsorption and separation of pollutants in wastewater by SA-based absorbents and freshwater harvesting by SA-based collectors. This review explores SA-based composites' composition-structure-construction designs and emphasizes the impact of materials like inorganic materials, functional polymers, and porous matrices and how they can be exploited for water treatment. It also highlights the mechanisms of contaminants adsorption and freshwater desorption of SA-based composites. Finally, the shortcomings and future orientation of SA-based composites are proposed, including performance optimization, structural modification, application expansion, and mechanism in-depth investigation. This review aims to offer a theoretical basis and technical guidance for the use of natural materials to respond to the shortage of freshwater resources.