Anisotropic Sliding Behaviors of Gas Bubbles upon Ferrofluid‐Infused Orthonormal Tracks (FOTs) Under Magnetic Stimuli

Abstract Manipulating gas bubbles in aqueous environment exhibits both scientific and technological significance in pressure sensors, mineral flotation, and sewage disposal. Recently, the emerging ferrofluid liquid‐infused porous surfaces (FLIPS) with excellent bubble magnetism‐responsive functions have attracted great attention. Although current studies have focused on the isotropic bubble motion on FLIPS, the dynamic bubble slipping behaviors on anisotropic FLIPS has not been clarified yet. Herein, a kind of ferrofluid‐infused orthonormal tracks (FOTs) with periodic micro‐grooved structures by one‐step femtosecond laser ablation is reported, exhibiting anisotropic slipping behaviors of underwater bubbles along two orthogonal directions on FOTs. Further investigation suggests that the bubble slipping distance, that is, the interfacial resistance, is subject to the ferrofluid infusion and the external driving velocities. It is revealed that the disparity of slipping resistance is mainly related to the interfacial dissipation and the anisotropic menisci reshaped by magnetic stimuli along two orthonormal directions of FOTs. Finally, relying on the anisotropic slipping motion of gas bubbles, typical applications including bubble screening and bubble‐assisted optical shutter are demonstrated. This study should provide new insight into bubble slipping dynamics on lubricant‐infused surfaces and prompt the development of optofluidics.