Development of composite micro-patterns on polymer film using repetitive ultrasonic imprinting

Ultrasonic imprinting is a novel process in which micro-patterns can be replicated on thermoplastic polymer with short processing time and low energy consumption. Ultrasonic imprinting uses ultrasonic vibration energy to soften thermoplastic polymer, and to replicate micro-patterns on the softened polymer surface from a patterned horn or mold. In this study, a new patterning method based on ultrasonic imprinting is proposed to develop composite micro-patterns using a simply-patterned mold. The proposed patterning technology uses repetitive ultrasonic imprinting in which a patterned replica is imprinted repeatedly on a rotated position. To implement this process for the development of composite micro-patterns, two-step repetitive imprinting with 90° rotation was performed using a prism-patterned mold, from which pyramid patterns can be developed. This repetitive imprinting was then further applied to fabricate composite micro-patterns that contain prism and pyramid micropatterns on a single polymer film.