Periodic microstructuring of metal moulds using direct laser interference patterning for nanoimprint replicationWednesday (24.06.2020) 13:10 - 13:13 Room 1
Periodic structure in surfaces with feature sizes in micro- and nanoscale range are capable of modifying a wide range of surface properties, such as wetting, friction, anti-bacterial behavior and optical reflectivity. Among the vast developed technologies to fabricate periodic patterns, Nanoimprinting Lithography (NIL) is regarded as one of the most promising industrial-scalable processes for the parallel replication of structures at the micro- and nano-scale with high-precision and high-quality. However, the fabrication of large-area microstructured molds at low-cost and high processing speed is still challenging. A manufacturing method that fulfills these requirements is Direct Laser Interference Patterning (DLIP), since it is a one-step process that can be used to pattern periodic micro- and submicro-structures in metals, ceramics and polymers with processing speeds up to 1 m2/min. In this work, microstructures were fabricated employing four-beam DLIP on three different metals, namely Ni, Cr, and Cu, relevant for the mold production in NIL systems. A picosecond laser source emitting at a wavelength of 532 nm was used to structure periodic hole-like patterns with a spatial period of 5 µm. The results show that the quality and surface topography of the produced hole-like micropatterns are determined by the laser processing parameters, such as irradiated energy density and number of pulses. After laser manufacturing, the three studied metals were used as embossing molds to imprint micropatterns on polymethyl methacrylate (PMMA) foils using an electrohydraulic press. Topographical profiles demonstrate that the imprinted microstructures are comparable to the molds showing a satisfactory replication of the textures. The polymeric microlens arrays that showed the best surface homogeneity and overall quality were those embossed with the Cr molds. In contrast, the PMMA substrates embossed with the Ni and Cu stamps showed a low quality and a relatively small microlens diameter caused by the rough cavities sidewalls of these stamps.
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