© Wiley Periodicals, Inc. Mechanical Property Investigation of Soft Materials by Cantilever-Based Optical Interfacial Force Microscopy

Summary: Cantilever-based optical interfacial force microscopy (COIFM)was applied to the investigation of themechanical properties of soft materials to avoid the double-spring effect and snap-to-contact prob-lem associated with atomic force microscopy (AFM). When a force was measured as a function of distance between an oxidized silicon probe and the surface of a soft hydrocarbon film, it increases nonlinearly in the lower force region below ∼10 nN, following the Herzian model with the elastic modulus of ∼50MPa. Above∼10 nN, it increases linearly with a small oscil-latory sawtooth pattern with amplitude 1–2 nN. The pattern suggests the possible existence of the layered structure within the film.When its internal part of the film was exposed to the probe, the force depends o