Characterization of adhesion phenomena and contact of surfaces by soft colloidal probe AFM

Abstract

We present a method based on colloidal probe atomic force microscopy (AFM) to measure adhesion energies and to study other contact phenomena of surfaces. The method employs an elastomeric colloidal probe, rendering the contact area between probe and sample much larger as compared to standard atomic force microscopy techniques. The technique allows us to determine the contact area via microinterferometry and measure the applied forces at the same time. The adhesion properties can then be accessed by using the Johnson–Kendall–Roberts (JKR) approach, i.e. measuring (a) the contact area as a function of applied load, and (b) the elastic parameters and the thermodynamic work of adhesion. We test this method in ambient conditions as well as in aqueous media on well-known surface chemistries, and can clearly characterize the contributions of capillary in air, hydration forces and hydrophobic interactions in water. This novel method provides a means to study the contact behavior of soft colloids and enhanced sensitivity for adhesion measurements.