Multifuctional Janus Materials for Rapid One-Way Water Transportation and Fog Collection

Laser-Constructed Bionic Composite Fog-Collecting Surfaces with Efficient Nucleation Sites and Enhanced Water Transport

Fog collection effectively alleviates the current freshwater shortage; thus, enhancing its efficiency is crucial. Here, we report a novel bionic fog collection surface (Al@B-V) comprising composite superhydrophobic bumps integrated with superhydrophilic V-channel grooves. This surface, which has efficient fog nucleation points and enhanced water transport capabilities, effectively balances fog capture and water transport during the collection process, thereby achieving high-efficiency fog collection. Compared to ordinary aluminum-based surfaces, Al@B-V achieves a fog collection efficiency of up to 3.08 g·cm-2·h-1, three times higher than the original aluminum-based surface. Furthermore, the V-channel groove proposed in this study exhibits a water transport speed of up to 165 mm·s-1, which is remarkably approximately 80 times faster than the commonly used U-channel groove. Additionally, this V-channel groove can overcome gravity, transporting approximately 10 μL of liquid to the top even when placed at 90° inclination. It can directionally transport 10 μL of liquid over a distance of up to 151 mm on a plane. This novel microgroove design can be effectively applied in various fields, including liquid collection, directional transport, seawater desalination, microfluidics, and drug delivery.

Beetle-Inspired Dual-Directional Janus Pumps with Interfacial Asymmetric Wettability for Enhancing Fog Harvesting

Fog-harvesting devices (FHDs) have been widely explored and applied to alleviate the shortage of fresh water. However, during the fog collection process, how to maintain a balance between fog capture and water removal behaviors to enhance the water collection rate still remains a challenge. Herein, inspired by the Stenocara beetle, we combined a beetle-like Janus surface and the conventional cross-sectional Janus structure together, developed a simple spray-and-dry strategy to obtain three types of biomimetic asymmetric meshes, and explored the working modes for atmospheric fog collection. The surface wettability could be carefully controlled, and various asymmetric meshes with different water transportation behaviors were obtained. Through a detailed study of the fog collection process, we concluded that there existed three main working modes: Janus mode, hybrid mode, and Janus and hybrid mode. It was noted that the dual-directional Janus pump with the Janus and hybrid working mode balanced the fog capture and water removal ability and exhibited the highest water collection rate of 2478.73 mg m^-2 h^-1, which was 2.61 times more than that of the corresponding superhydrophilic mesh. Furthermore, the prepared dual-directional Janus pump showed superior mechanical durability and antibacterial ability. In general, this work was considered instrumental in the reasonable design of biomimetic asymmetric meshes and could provide references for efficient atmospheric fog harvesting.

Surface behaviors of droplet manipulation in microfluidics devices

In recent years, the rapid development of microfluidic technology has caused a revolutionary impact in the fields of chemistry, medicine, and life sciences. Also, droplet control is one of the most important technologies in the field of microfluidics. In order to achieve different degrees of droplet transport, the dynamic balance of the competing processes of droplet driving force and fluid resistance should be controlled to achieve good selectivity of droplet transport. Here, we focus on the principles of droplet transport in microfluidic devices, including the driving forces for droplet transport in fluids and the effects of transport properties on droplet transport. After that, the effects of external fields on the directional transport of droplets and the advantages and disadvantages of each external field in droplet transport are discussed in detail. Finally, the applications and challenges of droplet microfluidics in chemical, biomedical, and mechanical systems are comprehensively introduced.

Multi-Bioinspired Janus Copper Mesh for Improved Gravity-Irrelevant Directional Water Droplet and Flow Transport

A conceptually novel multi-bioinspired strategy based on structures and functions derived from the Namib desert beetle and lotus leaf is proposed in this paper. The proposed scheme synergistically combines the features of alternating wettability patterns and asymmetric wettability for improved directional water transport. Consequently, a Janus copper mesh, which substantially outperforms other single-bioinspired synthetic materials, is produced. The Janus copper mesh achieves directional self-transportation of tiny water droplets and continuous water flow in a gravity-irrelevant or an anti-gravity manner without energy consumption. This depends on the asymmetric wettability and alternating hydrophobic-hydrophilic wettability patterns on the hydrophobic surface of the mesh. In particular, Janus copper shows remarkable selective directional water transport in a water-oil system, rendering it a promising candidate for practical applications.

Directional Water Transport Janus Composite Nanofiber Membranes for Comfortable Bioprotection

The Janus membrane has a huge prospect for personal comfortable protection. However, there still is a huge imbalance between the comfort and protection of the existing Janus membrane. There is an urgent need to further improve the comprehensive performance of the protective membrane to realize both protection and comfort. Herein, we report the Janus membrane with directional water transport capacity and dust rejection performance by compounding the polyvinyl chloride hydrophobic nanofiber membrane and polyamide-6 blended polyvinyl pyrrolidone hydrophilic nanofiber membrane. This Janus composite nanofiber membrane exhibited an excellent dust rejection efficiency of 99.99%, air permeability of 42.15 mm/s, which was 76 times that of the commercial waterproof and breathable PTFE membrane, water vapor transmission rate of 4.89 kg/(m² × 24 h), and accumulative one-way transport capacity of 888.7%. In addition, the breakthrough pressure of the Janus membrane in the reverse direction (i.e., hydrophilic layer to hydrophobic layer) was four times that in the positive direction (i.e., hydrophobic layer to hydrophilic layer), suggesting it to be a potential substrate for comfortable bioprotection with a comprehensive protection capability.