Direct Visualization of the Behavior and Shapes of the Nanoscale Menisci of an Evaporating Water Droplet on a Hydrophilic Nanotextured Surface via High-Resolution Synchrotron X-ray Imaging

Challenges and strategies for commercialization and widespread practical applications of superhydrophobic surfaces

Superhydrophobic (SH) surfaces have progressed rapidly in fundamental research over the past 20 years, but their practical applications lag far behind. In this perspective, we first present the findings of a survey on the current state of SH surfaces including fundamental research, patenting, and commercialization. On the basis of the survey and our experience, this perspective explores the challenges and strategies for commercialization and widespread practical applications of SH surfaces. The comprehensive performances, preparation methods, and application scenarios of SH surfaces are the major constraints. These challenges should be addressed simultaneously, and the actionable strategies are provided. We then highlight the standard test methods of the comprehensive performances including mechanical stability, impalement resistance, and weather resistance. Last, the prospects of SH surfaces in the future are discussed. We anticipate that SH surfaces may be widely commercialized and used in practical applications around the year 2035 through combination of the suggested strategies and input from both academia and industry.

The challenges, achievements and applications of submersible superhydrophobic materials

Superhydrophobic materials have been widely reported throughout the scientific literature. Their properties originate from a highly rough morphology and inherently water repellent surface chemistry. Despite promising an array of functionalities, these materials have seen limited commercial development. This could be attributed to many factors, like material compatibility, low physical resilience, scaling-up complications, etc. In applications where persistent water contact is required, another limitation arises as a major concern, which is the stability of the air layer trapped at the surface when submerged or impacted by water. This review is aimed at examining the diverse array of research focused on monitoring/improving air layer stability, and highlighting the most successful approaches. The reported complexity of monitoring and enhancing air layer stability, in conjunction with the variety of approaches adopted, results in an assortment of suggested routes to achieving success. The review is addressing the challenge of finding a balance between maximising water repulsion and incorporating structures that protect air pockets from removal, along with challenges related to the variant approaches to testing air-layer stability across the research field, and the gap between the achieved progress and the required performance in real-life applications.

Direct Visualization of Microscale Dynamics of Water Droplets on under-Oil-Hydrophilic Membranes by Using Synchrotron White-Beam X-ray Microimaging Techniques

Despite considerable academical and practical interests on separation of water-in-oil emulsion via special wettable membranes, fundamental understanding on microscale dynamics of water droplets on under-oil-hydrophilic membranes (UOHMs) at early stages during separation is still very preliminary due to temporal and spatial resolution of existing visualization techniques. To this end, we here succeed in a direct microscopic visualization of separation processes of water droplets on the UOHMs by employing a high-speed, two-dimensional synchrotron white-beam X-ray microimaging technique. During the separation of water-in-oil emulsion, microscale dynamic behaviors of water droplets on hydrophilic membrane surfaces immersed in the different oil media (i.e., hexane, kerosene, and light and heavy mineral oils) and oil films between water droplets and membrane surfaces are visualized and analyzed.