Mechanical contact imaging using fluorescence techniques

This thesis explores the use of fluorescence microscopy to study mechanical contacts at microscopic and nanoscopic scales. By employing multi-asperity contacts of soft (poly methyl methacrylate) and hard (glass) spheres with varying surface roughness on fluorescent molecular rotor-functionalized glass surfaces, the research provides insights into contact mechanics and molecular sensing. The fluorescence properties of the molecular rotor from dicyanomethylenedihydrofuran (DCDHF) family are utilized to probe these interfaces, providing a deeper understanding of nanoscale contact mechanics and molecular environments.
In the realm of contact mechanics, the effects of material stiffness and surface roughness on contact areas were investigated using diffraction-limited and single-molecule super-resolution fluorescence microscopy. These studies enabled in situ imaging of rough contacts, revealed nanoscopic contact areas, and demonstrated the influence of roughness and material properties on real contact area formation. These studies highlight critical length scales relevant to bridging theoretical contact mechanics models and practical applications.
The molecular sensing studies examine the fluorescence responses of DCDHF rotor molecules at mechanical contact interfaces and in diverse solid-state environments. These investigations reveal microenvironmental effects on ensemble and single-molecule fluorescence, shedding light on the mechanisms behind solid-state fluorescence blinking and its role in high-contrast, super-resolution contact imaging.
Together, these findings deepen our understanding of nanoscale contact mechanics and molecular sensing in solid-state systems, paving the way for innovative applications in materials science and molecular imaging.