RESEARCH PAPER Fabrication of high-aspect-ratio polymer nanochannels using a novel Si nanoimprint mold and solvent-assisted sealing Y. H. Cho • J. Park • H. Park • X. Cheng • B. J. Kim • A. Han Received: 7 July 2009 / Accepted: 14 September 2009 / Published online: 19 November 2009 Ó Springer-Verlag 2009 Abstract We present a low cost nanofabrication method to fabricate high-aspect-ratio (HAR) polymer nanochan- nels using a novel silicon nanoimprint mold fabrication technique and a solvent-assisted sealing method. These nanofluidic channels are being developed for single bio- molecule detection. The silicon nanoimprint mold fabri- cation process is based on the combination of anisotropic etching of silicon by potassium hydroxide (KOH) solution and the local oxidation of silicon (LOCOS) process. The resulting high-aspect-ratio silicon mold has smooth side- walls owing to the anisotropic KOH etching process along the silicon crystalline geometry as well as the LOCOS process. The nanostructures in the nanoimprint molds that form the nanochannels can be easily controlled by the initial micropattern sizes defined using conventional UV lithography and the oxidation time, making this technique a practical solution for low cost and high-throughput HAR silicon nanoimprint mold fabrication. Nanoimprint molds having aspect ratios of more than 1:5.5 (width: 200 nm, height: 1.1 lm, length: 1 cm) were successfully fabricated. Nanoimprinting technique was used to create poly(methyl methacrylate) (PMMA) nanotrenches out of this nanoimprint mold. A novel solvent-assisted sealing technique was developed in order to seal the HAR PMMA nanotrenches. This technique enables the gener- ation of nanochannels with various nanoscale dimensions without the need for complicated and expensive nanoli- thography tools. Keywords Nanochannel fabrication Á Nanoimprint lithography Á High-aspect-ratio nanostructure 1 Introduction Nanofluidic devices enable isolation, manipulation, and analysis of single biomolecules such as DNA and proteins, essential functions in the newly emerging field of nano- biotechnology (Huh et al. 2007; Craighead 2006; Tegen- feldt et al. 2004; Jo et al. 2007; Mannion et al. 2006). The radius of gyration of DNA (*400 nm) begins to match with the dimensions of nanofluidic channels, making nanochannels as one of the most effective tools for manipulating and analyzing the behaviors and movements of a single DNA strand (Jo et al. 2007; Mannion et al. 2006). Consequently, various fabrication techniques have been developed to meet the increasing demand for nano- fluidic devices, including nanochannels (Abgrall and Nguyen 2008; Perry and Kandlikar 2006). Top-down nanolithography such as focused ion beam (FIB) milling (Wang et al. 2006; Riehn et al. 2005), e-beam lithography (EBL) (Mannion et al. 2006; Tamaki et al. 2006), and scanning probe patterning (Mikayama et al. 2005) are some of the most straightforward methods to directly fabricate nanochannels. Despite their high-resolu- tion nanofabrication capabilities, they suffer from low throughput and high cost, making those techniques not suitable for mass production of nanofluidic devices. Being Y. H. Cho School of Mechanical Design and Automation Engineering, Seoul National University of Technology, Seoul, Korea J. Park Á H. Park Á X. Cheng Á A. Han (&) Department of Electrical and Computer Engineering, Texas A&M University, 235G WERC, TAMU 3128, College Station, TX 77843-3128, USA e-mail: arum.han@ece.tamu.edu B. J. Kim CIRMM, Institute of Industrial Science, The University of Tokyo, Tokyo, Japan 123 Microfluid Nanofluid (2010) 9:163–170 DOI 10.1007/s10404-009-0509-3