(452a) Interactions At Heterogeneous Surfaces: Regrouping Colloidal Interactions to Achieve Biomimetic Behavior

Textbooks on colloidal phenomena teach us to describe the electrostatic and dispersion interactions at interfaces using single parameters (Hamaker constants, surface potentials or charge densities), an approach which treats surface as uniform. Real surfaces, be they mineral, polymeric, or biological, present heterogeneous surface chemistry that complicates their interactions.  It is recognized that clustered rather than uniform presentation of attractive chemistries, for instance peptide sequences, enhances biological interactions.  Likewise, heterogeneity in charge and acid-base interactive groups has been invoked to explain colloidal instabilities and bacterial adhesion (that DLVO theory fails to predict).  A lack of understanding the energy landscape of real surfaces prevents their description by convolved versions of DLVO and related approaches.  Our lab, has, however, developed a series of model surfaces with well-characterized electrostatic heterogeneity and, through systematic variations in the interface, demonstrated how heterogeneity alters the surface forces.  This talk addresses the fundamental aspects of heterogeneous surface interactions and then translates the interactions to static and dynamic particle adhesion.  In particular, the influence of the energy and distribution of the heterogeneity will be addressed. The talk will then demonstrate how interactions at heterogeneous interfaces are particularly sensitive to physical interfacial features such as curvature and mechanical softness, and how this sensitivity can be exploited for separation and microfluidic sensing schemes.  Finally, the talk will address the role of heterogeneity in dynamic adhesion, from capture –hold-release protocols to continuous behaviors such as rolling.  These will be demonstrated with particles and spherical bacteria.  Throughout the talk, parallels between synthetic and biological interfaces will be drawn, probing the extent to which charge and other chemical clusters can be treated conceptually as biological receptors.