(452a) Direct Force Measurement Between Chemically Patterned Heterogeneous Surfaces

Artificially patterned surfaces provide a means of precisely tailoring the interactions between particles and surfaces.  As a consequence, such surfaces have a variety of potential uses in the fabrication of sensors and separation devices.  They can also provide a template to direct assembly at the micro and nanoscale.  However, to utilize artificially patterned surfaces for such applications, it is important to fully understand how patterning or surface heterogeneities alters surface forces.  One way patterning can alter surface forces is through control over the distribution and size of charge heterogeneities.  In this work, charge heterogeneities consisting of alternating stripes of a cationic polyelectrolyte were patterned onto mica via microcontact printing.  The force profile between the patterned surface and bare mica were directly measured in the surface force apparatus.  This force profile was compared to the force profiles between two bare mica surfaces and two surfaces uniformly coated in polyelectrolyte.  Comparisons were made between the measured force profiles and DLVO theory.  The effects of charge heterogeneity on surface forces have been explored experimentally through direct force measurement.