The anisotropic characteristics of natural fibrous sepiolite as revealed by contact angle, surface free energy, AFM and molecular dynamics simulation

► Sepiolite fibers are anisotropic with a surface free energy of 20.09 mJ/m2. ► Rough fiber surfaces imaged by AFM undergo substitution of Mg2+ at natural pH. ► MD simulation confirms a hydrophobicity level in the transition region. ► Sepiolite basal plane exhibits 3 Å space with water molecules.