Progress towards imaging biological samples with NSOM

Advancements in near-field scanning optical microscopy (NSOM) tip design as well as an interferometric feedback mechanism are presented for the common goal of imaging living biological samples under physiological conditions. The ability of a cantilevered tip to track the subtle topography changes of a fragile lipid film in an aqueous environment is demonstrated. In order to further the imaging capabilities, the probes have been chemically etched to reduce the spring constants of the tips, thereby lowering the forces imparted on the sample. An optical feedback mechanism used as an alternative to the conventional force feedback is also described. Utilizing this optical feedback mechanism, images have been obtained of fixed cells underwater. Finally, progress towards modifying the NSOM tip for chemical sensor applications is discussed in the context of eventually measuring ion fluxes through single protein channels. Together these advancements demonstrate the potential of NSOM for studying live cells.