Salvinia-inspired surfaces for enhancing the preservation of air plastrons under negative pressure

[Display omitted] •Blade coating and selective UV/O3 surface treatment are used for the fabrication.•Salvinia-inspired surfaces show enhanced ability for air plastron preservation.•Hydrophilic top surface constrains the movement of the air plastron.•Hydrophilic top surface decreases the negative critical pressure for detachment. The preservation of air plastron on a submerged microtextured surface under negative pressure has always been a challenge. In this study, the Salvinia-inspired surfaces (SIs) are fabricated and studied to enhance the preservation of air plastrons. The blade coating method and the selective UV/O3 surface treatment facilitated by an adaptive mask are applied for facile fabrication of the SIs with hydrophilic top but hydrophobic side and bottom. The air plastrons of both the SIs and regular hydrophobic surfaces (HBs) with singular and patterned cavities are experimentally visualized and theoretically deduced. The two-stage morphological behaviors of plastron expansion, together with quantitative geometric parameters, are compared between SIs and HBs under various negative pressures. The hydrophilicity effect on SIs effectively preserves the air plastron by reducing the critical negative pressure required for detachment by 90% compared to HBs. The ability of plastron preservation is proved on SIs with patterned cavities by hindering the coalescence of air plastrons. Our study benefits the cost-effective fabrication of Salvinia-inspired surfaces and provides a theory model to predict air plastron morphology and reveal its mechanism of enhanced air plastron preservation capability under negative pressure, which expands their underwater applications, such as migrating cavitation erosion. In the future, the capacity to retain air under high pressure requires further investigation.