Fabrication of various nanostructures poly(dimethylsiloxane) via chemical treatment and their mechanism

Abstract

Nanopatterning is fabrication of specific patterns in a nano scale. There are two methods for nanopatterning such as top down and bottom up. Top down method sculpts substrate using laser or electron beam. In this case, the expensive equipment is needed. Otherwise, bottom up method is a way to build up, and it is advantageous that it is possible to produce cheap and large capacity. Colloidal lithography and soft lithography belong to this method. Colloidal lithography is one of the simple and cheap method for fabricating nanostructures over a large area using self-assembled colloidal particles as a master template. Soft lithography, using Poly(dimethylsiloxane), is suitable to replicate the colloidal master mold. The PDMS is transparency, cheap, and non-toxic. Therefore, these two lithography techniques are a good candidate to fabricate nanopatterns because of no needed vacuum equipment and possible to room temperature process. Here I present the fabrication of various nanopatterns using honeycomb structured poly(dimethylsiloxane). The colloidal crystal, which is self-assembled by sub-micro polystyrene colloidal particles, is used to master mold for preparing honeycomb structured PDMS substrate. After cured the PDMS matrix, we can obtain pre-patterned substrate. The honeycomb size can be controlled by the size of colloidal particles. The PDMS polymer has two advantages to fabricate secondary structures. One is reduce the metal precursor through the residual silane groups in the PDMS matrix. The other is easily fabrication of secondary structures on the honeycomb structured PDMS using acid because of weakness about acid solution. In chapter 2, I report the characteristic of PDMS-gold nanoparticles composite and the secondary nanostructures on the honeycomb structure substrate. The gold precursor can be reduced in the PDMS matrix through the residual silane groups. Also, gold precursor act as catalyst to react between PDMS and EtOH. Therefore, the secondary patterns can be easily fabricated in a short time without expensive equipment. I fabricate two different patterns such as irregular metal structure, and thickened honeycomb structure via fabrication of PDMS-gold composite with different reaction condition. In chapter 3, I report the characteristic of acid treated PDMS matrix and the secondary nanostructures on the honeycomb structured PDMS matrix with acid treatment. The PDMS surface is easily modified and $NO_2$ gas is generated via acid treatment. The modified interface separates from original surface when $NO_2$ gas is emitted with post treatment. Finally, I fabricate various secondary sub-micro structures on the honeycomb structured PDMS substrate.