Studying deformable systems through experimental and theoretical approaches

© 2015 Dr. Chu WuIntermolecular and surface forces play a fundamental role in the physical world. Intermolecular forces dictate molecular interactions on the atomic level whilst surface forces govern the interaction of particles from the nano to the macro level through their respective surface properties. Thus an understanding of the intermolecular and surface forces is pivotal in developing new technologies (such as lab on a chip) or improving important existing industrial processes (such as raw materials refining). In this thesis, a complimentary experimental and theoretical approach was adopted to study the interaction of a wide range of dynamical systems. The experimental component utilised the atomic force microscope to drive together two deformable objects like gas bubbles or drive a rigid particle against a membrane. These experiments were then supplemented by theoretical modelling work which provided information about the interaction of the two surfaces that could not be detected experimentally. Through this complimentary technique, several observations and developments related to intermolecular and surface forces were made and are presented in this thesis. These results include the development of a model that characterises the hydrodynamics of porous anodic alumina membranes; discovering that increasing the retraction velocity at which two drops or bubbles are pulled apart is sufficient to cause their coalescence; attempting to characterize the strength and range of the hydrophobic effect in oil-water systems; and lastly developing a method of calculating the structural disjoining pressure as a function of separation between two semi-infinite plates separated by a nanoparticle solution before using this model to examine the unique features associated with structural forces in deformable systems