Hydrophobic/Oleophobic/Hydrophilic/Lipophilic Paper‐based Functional Materials

This chapter explores the mechanisms and applications of hydrophobic/oleophobic/hydrophilic/lipophilic paper-based functional materials. It begins by introducing wettability models, including Young's, Wenzel, and Cassie–Baxter models, to explain surface interactions. This chapter then defines four types of wetting interfaces—biphobic, hydrophobic/lipophilic, amphiphilic, and hydrophilic/oleophobic—and discusses their unique properties. Various preparation methods, such as physicochemical modification, surface coating, nanoparticle deposition, and chemical modification, are detailed for creating these materials. Applications span oil–water separation, self-cleaning surfaces, microfluidic devices, and smart responsive materials. This chapter highlights the potential of these materials in addressing environmental and industrial challenges, emphasizing their versatility and innovation in functional material design.