Molecular interfaces control chemical, physical, biological and tribological properties of surfaces at all scales and levels of complexity, including simple adsorbates and self-assembled monolayers (SAMs), multi-component bio-functionalized surfaces, and real-world lubricating coatings. Research in the section ranges from developing comprehensive analytical methods to understand model and realistic surfaces to designing and optimizing molecular interfaces that reduce fouling, preserve biological activity, or lower friction.
AFM of barnacle adhesive fibrils
Biointerfaces form when biomolecules interact with inorganic or synthetic solid surfaces. The Section aims to understand biointerfaces across a wide range of spatial and complexity scales and participates in interdisciplinary collaborations, both within NRL and externally. Optimizing the methods for surface attachment of biomolecules that preserves their biological activity and minimizes nonspecific adsorption is a focus area of research in the Section. The goal of understanding the molecular structure of biointerfaces extends to more complex cases such as biological films that mediate the attachment of cells and organisms to surfaces. A Navy-specific biofilm problem addressed by the Section is the analysis of the chemical and mechanical properties of barnacle adhesive proteins.
Tribology and adhesion behavior of complex surfaces is often dominated by the chemical and molecular structure of the contacting interfaces. The Section works on developing a fundamental understanding of the chemical and mechanical basis of interfacial processes in sliding and adhesive contacts. Current projects in the Section include 1) developing in situ methods to probe interfacial chemical and mechanical processes controlling friction and wear, 2) developing robust lubrication strategies for especially demanding Navy applications, 3) understanding how structure and surface chemistry of nanostructured materials influence friction and wear, and 4) developing new approaches to evaluate and model mechanics and chemistry of foul-release or anti-fouling surface treatments.
Bioinspired materials under development in the Section aim to exploit the design motifs that result in biomaterials having unique properties, such as superior toughness and mechanical properties of spider silk and structural proteins. Synthetic materials that mimic the nanostructure of such biomaterials offer the potential of large-scale production and of incorporating functions, e.g., conductivity and fluorescence, not found in the respective natural materials. An important biomimetic design strategy currently explored in the Section is based on nanostructured subunits that are constructed and polymerized using strong covalent bonds, while organized at the microscopic scale using weak and reversible bonds. These synthetic efforts in the Section are complemented by the ability to directly probe the optical and mechanical properties of nanostructured materials.
Quantitative surface analysis of molecular, biological, and tribological interfaces requires adapting or developing analytical techniques that can probe surface and interface properties of realistic systems, ideally in real time and in situ. The Section’s members are internationally recognized in many areas of surface analysis, including optical and electron spectroscopy of complex inorganic, organic, and biological interfaces, quantitative nanomechanics, and real-time in situ analysis of thin film interfaces involved in sliding and adhesion. The Section is particularly successful in addressing interdisciplinary problems, where it has the critical advantage of being able to combine multiple complementary analytical techniques in order to comprehensively characterize complex interfaces.