Chemical Patterning of Ultrathin Polymer Films by Direct-Write Multiphoton Lithography

摘要

We applied 2-photon laser ablation to write sub-diffraction nanoscale chemical patterns into ultrathin polymer films under ambient conditions. Poly(ethylene glycol) methacrylate brush layers were prepared on quartz substrates via surface initiated atom transfer radical polymerization (SI-ATRP) and ablated to expose the underlying substrate using the non-linear 2-photon absorbance of a frequency doubled Ti:Sapphire femtosecond laser. Single-shot ablation thresholds of polymer films were ~ 1.5 times smaller than that of a quartz substrate, which allowed patterning of nanoscale features without damage to the underlying substrate. At a 1/e² laser spot diameter of 0.86 µm the features of exposed substrate approached ~ 80 nm, well below the diffraction limit for 400 nm light. Ablated features were chemically distinct and amenable to chemical modification.