Single-molecule super-resolution microscopy is emerging as a promising analytical technique beyond typical biological applications into new areas such as materials science and nanotechnology. The ability image nanostructures non-invasively opens the possibility of direct in situ real-space observation at the nanoscale. We explore the capabilities of single-molecule super-resolution microscopy using lithographically patterned polymer thin films as model samples. Line and space patterns of varying pitch were written using electron-beam lithography, and the resulting super-resolution images were compared to the expected structures. Features as small as 20 nm are clearly resolvable. We then explore the effect of fluorophore orientation, which can alter the single-molecule point-spread function and reduce localization accuracy, but can also be used to report nanoscale chemical environment and dynamics in materials. This capability is demonstrated using polymer films that have been deformed by nanoimprint lithography, where mechanical stress is detected in areas as small as 15 nm through changes in the fluorophore orientation distribution. To further accelerate the transition of single-molecule methods from the biological space into materials science, we have tailored a photoswitchable fluorophore optimized for organic environments. The fluorophore is polymerizable, which greatly streamlines labeling strategies into a single step, where a small quantity is mixed with standard monomers and copolymerized to yield the functionalized material with no further purification. We find that this fluorophore is highly photostable, and we explore the photoswitching kinetics to understand the effect on imaging resolution. This feature is highly useful in photoactivated localization microscopy experiments. For example, in situ imaging is demonstrated in solvent-swollen polymer blends, where coarsening behavior and self-assembly is readily observed.

Single-molecule localization, orientation, and dynamics for super-resolution microscopy in polymer science

2019 Spring National Meeting

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