Optical-force-directed single-particle-based track etching in polystyrene films

Abstract

The establishment of optical trapping theory by A Ashkin almost half a century ago led to the trapping and manipulation of micro-/nano-objects and atoms by laser beams, which is now applied in many fields. However, in a complex system where multi-physical effects interact synergistically, light–matter interaction becomes dynamic and complicated and is still poorly understood. Here, by utilising plasmonic heating, nanolithography of polystyrene (PS) films and nanomanipulation of gold nanoparticles are realised. We find that laser power and PS film thickness as well as particle shape strongly affect the etching behaviour of the PS films, which is a synergistic effect of photothermal ablation and optical forces. Theoretical calculations and simulations rationalise the proposed mechanism, which is also verified by experimental observation. This understanding not only sheds light on how the synergistic effect of photo-ablation and optical forces acts on the particles and polymer films, but also provides a guideline for light-directed single-particle-based nanolithography and nanomanipulation.