Sub-micrometer and nanoscale imprinting on large-area foils using high-pressure underwater shock waves

Abstract

Laser shock imprinting (LSI) is an emerging method for creating sub-micrometer and nanoscale reliefs on thin metal foils. This report proposes using underwater shockwaves, generated by detonating an explosive charge, for high-quality imprinting as an alternative to LSI. The nanoscale relief of a polycarbonate mold with 740 nm periodic grooves was replicated on an Al foil using an underwater shockwave. Underwater detonation of a high explosive creates a shockwave with pressure ≥ 1 GPa that lasts for more than 100 ns, significantly longer than that for LSI. This provides a relief depth equal to 90% of the depth of the grooves on the mold. This mold filling efficiency is the best achieved by shock imprinting reported to date. In addition, underwater shockwaves can be used for imprinting over a large area in a single shot. Furthermore, the thickness of the Al foil can be increased in comparison to that for LSI. Using a simplified 1-D model of foil acceleration, we showed that increasing the foil thickness decreases the imprinting accuracy. This study paves new ways for large-area manufacturing of micro/nanopatterns on metals that would be especially beneficial for future applications in the fields of plasmonics and metasurfaces.

Keywords

• Nanoimprinting
• Explosive
• Underwater shock wave
• High strain rate