Surface Chemical Modification of Poly(dimethylsiloxane)-Based Biomimetic Materials: Oil-Repellent Surfaces

The oil-repellent performance of a poly(dimethylsiloxane)-based biomimetic replica (PDMS-replica) was tuned by modifying its surface chemical composition. PDMS-replica possessing a complementary combination of hierarchical roughness and mixed -CF3 and -SiCH3 terminal functionality was prepared in the presence of a surface-modifying agent, using nanocasting based on soft lithography. PDMS-replica showed superhydrophobicity and enhanced oil repellency, theta(oil) similar to 86 degrees. PDMS-replica was further modified with silica nanoparticles followed by chemical vapor deposition of (heptadecafluoro-1, 1, 2,2-tetrahydrodecyl)trichlorosilane. The -CF3 terminal, silica-modified PDMS-replica (i.e., PDMS-replica(silica/CF3)) showed both superhydrophobic and high oil-repellent properties (advancing theta(oil) similar to 120 degrees). During the process of each chemical transformation, the surface pattern present on PDMS-replica was preserved and monitored using scanning electron microscopy. Surface chemical compositions of PDMS-replica and PDMSsilica/CF3 were determined using X-ray photoelectron spectroscopy. Understanding the extent of adhesion on a biomimetic replica possessing different surface chemical compositions and roughness would provide fundamental information for various applications.