Femtosecond Laser Direct‐Writing Ablation of Transparent Fluoropolymer Toward Super‐Resolution Imaging of Cell Movements

Abstract

AbstractLive imaging of living cells in 3D micro/nano‐environment is important for advanced biological studies. An issue for super‐resolution imaging is refractive index mismatch between the materials used for imaging platform and medium containing cells (water). Fluoropolymer CYTOP is the ideal platform material due to its refractive index close to that of water. Herein, femtosecond laser (220 fs) is exploited to ablate CYTOP at three laser wavelengths of 257, 515, and 1030 nm. Linear power dependences of the ablation rate obtained for all wavelengths indicate that ablation mechanisms of CYTOP are attributed to the production of fragmented CYTOPs (frag‐CYTOPs) inside the film to induce efficient light absorption for subsequent laser pulses. The frag‐CYTOPs can effectively absorb UV–Vis light, whereas those left behind generate green fluorescence. Importantly, the shortest wavelength of 257 nm offers the best ablation quality in terms of surface smoothness and low fluorescence with the highest ablation rate. We elucidate that the refractive‐index matching of CYTOP/water is effective for clear imaging of shapes/fluorescence of cells on 3D structures, e.g., HeLa cells on V‐shaped trenches. The fabrication of a microscopic 3D fluorescence code tag embedded in the CYTOP films is further demonstrated.