Adhesion and friction studies of microsphere-patterned surfaces in contact with atomic force microscopy colloidal probe

Many studies have shown that surface roughness affects the adhesion and friction forces. One effective approach of reducing adhesion and friction forces between contacting interfaces is to create textured surfaces or surface modification, which is especially beneficial for micro/nano systems (e.g. MEMS/NEMS) that normally have smooth surfaces and are subjected to small applied forces. This paper presents the results of adhesion and friction studies on the ordered polystyrene microsphere-patterned surfaces (MSPS) with two types of patterned asperities fabricated by the spin-coating technique. A 1-Octadecanethiol (ODT) self-assembled monolayer was deposited on the MSPS to study the effect of hydrophobic coating on the adhesion and friction of patterned surfaces. The morphologies of MSPS were characterized by atomic force microscope (AFM) and field emission scanning electron microscope (FESEM). The adhesion and friction on the MSPS were studied by AFM using a colloidal probe. The results show that the micro-patterned surfaces have effectively reduced adhesion and friction compared to the flat surface because of the reduction of the contact area between contacting interfaces. Introducing a hydrophobic film to the microsphere-patterned surface can further reduce the adhesion and friction forces due to the reduction of meniscus-mediated adhesion and friction between interacting bodies.