Fabrication and Application of Micro/Nano Hybrid PDMS Mold
Date Issued
2010
Date
2010
Author(s)
Huang, Yi-Hao
Abstract
Micro contact printing (μCP), nano contact printing (nCP) and transfer stamping processes have been developed with the goal of direct fabrication of microstructures without residual layers. But in real cases, residual layers are frequently observed. The inks often reside in cavities of the mold structure during spin coating; these inks might be left on the substrate when the stamping or printing pressure deforms the mold.
In this research, we propose a novel method to solve the residual layer problem by using PDMS mold with micro/nano hybrid structures. The mold consists of hydrophobic nanostructures and micro structures. The hydrophobic property of nanostructures can avoid the sticking of inks in the cavities and thus prevent residual layers.
We first fabricated AAO (anodic aluminum oxide) template, and this template was then used as a mold to replicate nanostructures on PC (polycarbonate) film by gas-assisted hot embossing process. Next, we performed the second gas-assisted hot embossing process using this PC film with nanostructures as the substrate and employed a mold with micro structures to replicate micro structure to this PC substrate. After that, a PC film of protruded microstructures with AAO nanostructures was obtained. This PC film with nano/micro structures was then used as a master mold, and the PDMS (polydimethylsiloxane) resin was cast onto this master mold. After cure, a PDMS mold of hydrophobic nanostructures on surface of micro-cavity was obtained.
These are three major aspects in this research: 1. AAO templates with different geometrical characteristics of nanopores were fabricated through varying the AAO processing parameters, and the hydrophobic properties displayed in the final PDMS surface using these AAO templates were investigated. The hydrophobic property of PDMS’s surface has been significantly improced; the contact angle on the flat PDMS with nanostructures is nearly 150°, higher than that on the smooth PDMS surface, which is about 115°. 2. Micro/nano hybrid structures were fabricated on PC film using two continual gas-assisted hot embossing processes with AAO template for nanostructures and stainless mold for microstructures. PDMS was cast on this PC film as the master mold to fabricate the PDMS mold with hybrid micro/nano structures. 3. The transferred patterns using the micro/nano hybrid mold showed significantly less residual layers, compared with these transferred results using a conventional PDMS mold without hydrophobic nanostructures. The PDMS mold with hybrid micro/nano structures was used to transfer photoresist patterns, which served successfully as the mask patterns onto copper substrate during the subsequent Cu etching, showing the promising potential in applying such PDMS mold with hybrid micro/nano structures in photolithography.
Subjects
transfer stamping process
hydrophobic nanostructures
anodic aluminum oxide
micro/nano hybrid PDMS mold
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