Oleophobic

Oleophobic describes a surface property in which oils resist wetting. On an oleophobic surface, oil droplets tend to bead up and remain separate from the surface rather than spreading, allowing the droplets to roll away easily. This behavior is largely governed by surface energy: coatings or materials that present low surface energy reduce the affinity of oils for the surface. Oleophobicity is not synonymous with hydrophobicity, though a surface can be both oleophobic and hydrophobic depending on its chemical composition.

Oleophobicity is typically measured by the oil contact angle and the oil droplet’s sliding or roll-off angle. A high oil contact angle and a low roll-off angle indicate stronger oil repellency. Achieving durable oleophobicity often involves low-energy materials such as fluorinated polymers or fluorinated silanes, sometimes combined with micro- or nano-scale surface texturing to reduce contact with oil.

Common applications include protective coatings on smartphone screens, eyeglasses, and camera lenses to reduce fingerprinting and staining; oleophobic coatings on cookware and kitchen surfaces to minimize oil-based residues; and oil-repellent textiles and medical devices where easy cleaning and reduced staining are advantageous. In addition, oleophobic coatings can aid in controlling contamination in sensitive analytical and optical instruments.

Limitations and challenges include wear from abrasion, contamination, and aging, which can degrade oleophobic performance. Some oils with strong solvency can penetrate or disrupt coatings, necessitating reapplication or maintenance to restore repellency.