Using silicon molds for ultrasonic embossing on Polymethyl Methacrylate (PMMA) substrates

Abstract

This paper presents ultrasonic embossing using silicon molds to replicate microstructures on Polymethyl Methacrylate (PMMA) substrates. The pattern of the silicon mold consists of micro grooves with different sizes. The molds were fabricated by wet etching, and both concave and convex types were fabricated. The effects of the processing parameters on replication quality, including average microstructure depth, uniformity and the location-related replication depth were investigated via orthogonal experiments. The results show that the ultrasonic amplitude is the most important parameter for replication depth. The ultrasonic time benefits the accumulation of the heat, so it also influences replication depth. As for ultrasonic force, it has less influence on replication depth but significant influence on replication uniformity. The width of the grooves of the high density patterning molds ranged from 10 to 30 μm, and the center distance between the two microstructures from 20 to 50 μm in our experiments. The concave molds were intended to reach higher replication depth than that of convex molds with the same micro grooves. The average replication depth reached 98 %, and the uniformity on one chip reached 99 % with an area of 11 × 11 mm. All experiments were finished in 60 s, which is more efficient than the hot embossing technique, thus this paper provides a potential method for medium-sized bulk production and rapid fabrication for polymer microcomponents.