Experimental study of the interactions and dynamics at interfaces using newly developed AFM techniques

Abstract

Compared to the bulk properties of material, our fundamental understanding of the interactions and dynamics at the material interface are still very limited. The lack of progress is partially because the interfacial interactions are extremely sensitive to the nanoscale distance at which the measurements are made, and the interfacial dynamics are easily disturbed by defects and impurities at the interface. Well-controlled experimental systems with tunable interfacial properties together with surface-sensitive experimental tools and analysis methods are needed for the study of the interactions and dynamics at interfaces. In this talk I will present the development of new atomic force microscopy (AFM) probes and techniques and their applications in the investigation of novel interfacial phenomena and understanding of the underlying physics.

 

Three interesting problems are studied at different interfaces: In the first experiment, I conduct direct AFM measurements of capillary force hysteresis and of the relaxation of a circular moving contact line formed on a long micron-sized hydrophobic glass fiber intersecting a liquid-air interface. The second experiment studies the plasmonic interactions of light with a nano-structured metallic surface using the dynamic mode AFM. In the third experiment, I conduct a non-contact measurement of the viscoelastic properties of a nanometer-thin polymer film in a liquid medium using the frequency modulation AFM. In addition, I apply this new AFM technique to simultaneously measure the morphology and spatial distribution of the elastic modulus of live cells and their temporal evolution during different stages of cell growth and division. This thesis work thus provides new techniques and perspectives of AFM and leads to better understanding of the interactions and dynamics at interfaces.