Water Spider-Inspired Nanofiber Coating with Sustainable Scale Repellency via Air-Replenishing Strategy

Self-Driven Gas Spreading on Mesh Surfaces for Regeneration of Underwater Superhydrophobicity

Underwater superhydrophobic surfaces stand as a promising frontier in technological applications such as drag reduction, antifouling, and anticorrosion. Unfortunately, the air film, known as the plastron, on these surfaces tends to be unstable. To address this problem, active approaches have been designed to preserve or restore plastrons. In this work, a self-driven gas spreading superhydrophobic mesh (SHM) surface is designed to facilitate recovery of the plastron. The immersed SHM can be "wetted" by gas, even when the plastron is removed. We demonstrate that the injected gas can spread spontaneously along the SHM over a large area, which greatly simplifies the plastron replenishment process. By incorporating a locally coated gas-producing layer, we achieve rapid in situ plastron recovery and long-term immersion stability, extending the plastron lifespan by at least 48 times. We also provide a framework for designing an SHM with suitable structural dimensions for gas spreading. Furthermore, an SHM with asymmetric structural dimensions enables unidirectional gas transport by the capillary pressure difference. This SHM surface shows excellent drag reduction properties (37.2%) and has a high slip recovery coefficient (73.4%) after plastron loss. This facile and scalable method is expected to broaden the range of potential applications involving nonwetting-related fields.

Manipulation of bubble collapse patterns near the wall of an adherent gas layer

This paper aims to apply experimental methods to investigate the effect of the thickness of gas layers on the wall on the collapse direction of spark-induced bubbles. In the experiment, two high-speed cameras synchronously record the time evolution of the bubbles and the corresponding parameters such as the normalized collapse position and bubble collapse time. Experiments yielded results for individual bubbles over a range of normalized distances from 0 to 4.0 for different air layer thicknesses. Based on the morphology of the bubbles, the experimental jets were visualized into six different modes, namely, forward jet (FJ), merging jet (MJ), bidirectional jet (BJ), reversing jet (RJ), forward followed by reversing jet (FRJ), and non-directional jet (NDJ). The height of the air layer on the wall is affected by the fluctuation of the bubble volume and shows the opposite trend to the change of the bubble volume. The air film reaches its maximum height when the bubble collapses, which affects the final jet pattern. In addition, as the thickness of the air layer increases, the center of the bubble gradually migrates away from the wall. The different collapse modes and the migration of the bubble centers have positive significance for reducing cavitation erosion in engineering.