Extreme-Pressure Imprint-Directed Micropatterning of Self-Assembled Nanostructures

Abstract

Extreme pressure imprint lithography (EPIL) offers a simple route to impart microscale geometries without thermal or chemical preconditioning, yet its integration with block copolymer (BCP) self-assembly remains relatively unexplored. Here we report an EPIL-directed micro- and nanopatterning strategy that couples mold-driven microscale confinement with thickness-dependent self-assembly of sphere-forming PS-b-PDMS thin films. When a spin-cast BCP film is imprinted with a rigid Si mold, the imposed height contrast, from a few nanometers on compressed mesas to tens of nanometers inside trenches, governs whether no pattern, monolayer, or double-layer nanostructures appear after thermal annealing and RIE treatment. On ductile Al substrates, simultaneous metal deformation and pressure-driven BCP redistribution create hierarchical patterns, in which polymer accumulation on the raised microfeatures after imprint release leads to selective formation of SiO x nanostructures. This EPIL-directed self-assembly approach provides large-area and shape-versatile patterning enabled by mechanically imposed confinement across rigid and ductile substrates, suggesting a broadly applicable route for hierarchical pattern engineering across multiple length scales.