Replication of polyethylene nano-micro hierarchical structures using ultrasonic forming

Abstract

We present the replication of polyethylene (PE) nano-micro hierarchical structures and their application for superhydrophobic surfaces. A commercial ultrasonic welding system was used to apply ultrasonic vibration energy to the forming of nano-micro hierarchical structures. To evaluate ultrasonic formability, Ni nanomold and nano-micro hierarchical mold were designed and fabricated. The optimal weld times were 1.5 s and 3.0 s for PE nanoprotrusions and nano-micro hierarchical structures, respectively. The forming process was conducted at atmospheric pressure. The PE structures were well replicated without a vacuum. The trapped air in the microcavity of the nano-micromold was dispersed and absorbed into the molten PE. Ultrasonic nano-microreplication technology showed an extremely short processing time and did not require a vacuum environment. To investigate the applicability of ultrasonic forming, the fabricated nanoprotrusions and nano-micro hierarchical structures were coated with plasma polymerized fluorocarbon (PPFC) of a hydrophobic nature and were applied to modify superhydrophobic surfaces. The contact angle was increased from 106 • (smooth surface) to 125 • (nanostructured surface) and finally to 160 • (nano-microstructured surface) so that the surface became superhydrophobic.

Replication of micro/nano-scale features by micro injection molding with a bulk metallic glass mold insert

“…The traditional siliconbased molds are brittle and have a limited longevity [6,14,15]. Metal, such as nickel stamper, has been widely used as micro/nano scale molds [8].…”

A general, rapid and solvent-free approach to fabricating nanostructured polymer surfaces

“…Benefiting from ultrasonic vibration, the involvement of involatile solvent and the preheat of AAO template and/or polymer were avoided in our approach, which is advantageous over ultrasonic vibration-assisted hot embossing or nanoimprint lithography approach [25][26][27][28]. Additionally, the heat induced by ultrasonic vibration completely dissipated within several seconds after the vibration was terminated.…”

Heat generation and distribution in the ultrasonic hot embossing process

“…Several papers have been published on ultrasonic hot embossing and its variants Liu and Dung 2005;Mekaru et al 2007a, b;Khuntontong et al 2008;Yu et al 2009;Lee et al 2010;Altmann et al 2012;Šakalys et al 2015;Planellas et al 2014), but up to now only few investigations have been performed on the physical processes during fabrication. Liu and Dung measured the temperature inside of a polymethylmethacrylate (PMMA) plate, 2 mm in thickness, with thermocouples inserted into drilled holes and discovered that in less than 0.5 s temperatures were rising up to 200 °C (Liu and Dung 2005).…”