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Open AccessArticle

Development of Micropatterns on Curved Surfaces Using Two-Step Ultrasonic Forming

1
Department of Mechanical System Design Engineering, Seoul National University of Science and Technology, Seoul 01811, Korea
2
R&D Department, Rastech Co. Ltd., Daejeon 34037, Korea
*
Author to whom correspondence should be addressed.
Micromachines 2019, 10(10), 654; https://doi.org/10.3390/mi10100654
Received: 29 August 2019 / Revised: 20 September 2019 / Accepted: 26 September 2019 / Published: 28 September 2019
(This article belongs to the Special Issue New Approaches to Micropatterning)
Nanoimprint lithography (NIL) is a micro/nanoscale patterning technology on thermoplastic polymer films, and has been widely used to fabricate functional micro/nanoscale patterns. NIL was also used to develop micro/nanoscale patterns on curved surfaces by employing flexible polymer stamps or micropatterned metal molds with macroscopic curvatures. In this study, two-step ultrasonic forming was used to develop micropatterns on a curved surface out of a flat metal stamp, by connecting ultrasonic imprinting and stretching processes. Ultrasonic imprinting was used to replicate functional micropatterns on a flat polymer film, using a flat ultrasonic horn and micropatterned metal stamps with prism and dot micropatterns. An ultrasonic stretching process was then used to form a curvature on the patterned film using a curved ultrasonic horn and a soft mold insert, to avoid damage to the pre-developed micropatterns. The ultrasonic horn was designed to have three different tip radii, and the resulting forming depth and curvature formation were investigated experimentally. As a result, three different curved surfaces containing two different micropatterns were obtained. The developed curved films containing micropatterns were then evaluated optically, and showed different optical diffusion and illumination characteristics according to the film curvature and micropattern type. These results indicate that the proposed technology can extend the functionality of conventional micropatterned products by imposing appropriate curvatures. View Full-Text
Keywords: micropattern; ultrasonic imprinting; ultrasonic stretching; functional surface; curved surface micropattern; ultrasonic imprinting; ultrasonic stretching; functional surface; curved surface
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MDPI and ACS Style

Park, J.-H.; Park, K. Development of Micropatterns on Curved Surfaces Using Two-Step Ultrasonic Forming. Micromachines 2019, 10, 654.

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