A\nUniversal Strategy for the Preparation of Dual Superlyophobic\nSurfaces in Oil–Water Systems

There\nare some methods to prepare superwetting surfaces with underwater\nsuperoleophobicity (UWSOB) or underoil superhydrophobicity (UOSHB),\nbut it is still thorny to put forward a universal strategy for constructing\ndual superlyophobic surfaces in oil–water systems due to a\nthermodynamic contradiction. Herein, a universal strategy was proposed\nto prepare the dual superlyophobic surfaces in oil–water systems\nonly via delicately controlling surface chemistry, that is, adjusting\nthe ratios of superhydrophilic and superhydrophobic counterparts in\nthe spray solution. Three types of materials, attapulgite (APT), TiO₂, and loess, were chosen to prepare a diverse series of mixed\ncoatings (mass gradient of superhydrophobic counterparts from 0 to\n100 wt %). With the proportion of each superhydrophobic counterpart\nincreasing, the underwater oil contact angle (θ_o/w^*) of each mixed\ncoating slightly decreased but still was more than 150°, that\nis, UWSOB. In contrast, the underoil water contact angle (θ_w/o^*) was significantly\nimproved, realizing the transformation from UOHL (or UOHB) to UOSHB.\nMore importantly, the respective mass ratios of superhydrophobic counterparts\nin the resulting mixed coatings of APT, TiO₂, and loess\nwere finally determined to be 0.3, 0.4, and 0.2, respectively. Taking\nAPT as a model, a train of mixed APT coatings with different superhydrophobic\ncomponents were systematically characterized and analyzed. Finally,\nthe prepared superlyophobic separation mesh in oil–water systems\nwas applied to the separation of various surfactant-stabilized oil–water\nemulsions. We envision that this universal strategy we proposed will\nshow a significant application potential in addressing scientific\nand technological challenges in the field of interfacial chemistry\nsuch as oil–water separation, microfluidics, microdroplet manipulation,\nantifogging/icing, cell engineering, drag reduction, and so forth.