Effect of Surface‐Lubricant Compatibility on Bubble Formation in Lubricant‐Infused Surfaces

Lubricant‐infused surfaces (LIS) are functional materials with desirable properties, including microscale drag reduction. Previous work has shown that large drag reduction arises from the nucleation of bubbles on regions depleted of lubricant, where the underlying hydrophobic substrate contacts water. However, this evidence was obtained on surfaces in which the lubricant only partially wetted the substrate in air. A key question is whether microbubble nucleation also occurs when the substrate is completely wetted by the lubricant in both air and water. In this study, laser‐structured steel surfaces were produced using femtosecond laser treatment and functionalized with either liquid‐like polydimethylsiloxane (PDMS) brushes, fully wetted by silicone oil in air, or perfluorinated layers, which silicone oil only partly wets in air. Silicone oil‐infused surfaces were depleted by repeated water jetting, and the presence of an interfacial plastron or bubbles was quantified using microscopy. Fully infused LIS showed no bubbles on either system, but with progressive depletion, bubbles and subsequently plastron layers appeared, confirming that bubble formation occurs on LIS regardless of surface chemistry. Scalable laser texturing and the stabilization of gas bubbles by lubricant layers offer promising avenues for practical drag reduction applications.