Spatial resolution in polymerization of sample features at nanoscale

Abstract

Recent developments in laser nanotechnologies allow overcoming optical limitations at the $100\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$ level of spatial resolution. However, at such distances spatial restrictions on nanostructuring can be imposed by nonlocal response of the media. In the present paper, we consider nanostructuring by means of locally initiated radical polymerization of multifunctional monomers. Such local initiation can be provided, for instance, by femtosecond laser techniques. We theoretically analyze the limitations imposed by diffusion on the formation of two separate nanofeatures such as voxels, rods, and plates. Owing to the percolationlike transition occurring during the polymerization process, mathematical criteria for possible separation of such features are formulated. We develop a theoretical approach by consecutively taking into account diffusion of radicals of growing length. This approach allows us to estimate a characteristic spatial scale which determines the spatial resolution for the particular polymerizing system. For several realistic polymerizable resins, this resolution limit was estimated to be on the order of $10--100\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$.