Mechanical performance of polymer protuberances induced by dynamic lithography

Polystyrene is a widely used transparent polymer for applications in functional nanocomposites and cell culture. Atomic-scale protuberances can be induced on the surfaces using atomic force microscope dynamic lithography, satisfying the requirement for atomic-scale feature sizes in atomic and close-to-atomic scale manufacturing. A further requirement is minimizing the fabrication damage to preserve surface performance. In contrast to conventional mechanical machining that typically produced grooves, channels, or bundles, the formation mechanisms and damage assessment of protuberance have remained unclear despite of investigations over the past two decades. To this end, advanced techniques including atomic force microscope, scanning electron microscope, and transmission electron microscope were employed to systematically analyze the morphology, subsurface structure, and mechanical responses of polystyrene protuberances. Surface and subsurface characterization confirmed the stable formation of continuous protuberance through localized plastic deformation under tip penetration, without observed subsurface damage. Mechanical analysis revealed that protuberance regions exhibited enhanced Young’s modulus and dissipation compared to pristine surfaces, reflecting changes in chain mobility. These findings provide new insights into the deformation mechanisms of polymers under high strain rates and advance the understanding of vibration-assisted mechanical lithography approach for ACSM.