Research On The Fabrication Approach And Theory For Thermoplastic Polymer Two Dimensional Nanochannels

With the feature size in nanoscale, the nanofluidic chips have extensive application prospects in chemical detection, biological analysis, medical engineering and other fields. The two-dimensional (2D) nanochannel is a type of component of the nanofluidic chip with significant practical value. Because of the dimensions of2D nanochannels are comparable to those of biomolecules, these components have numerous advantages to study molecular behavior (such as DNA and proteins) at single-molecule levels. However, the fabrication of2D nanochannels mainly relies on expensive equipments with nanometer resolution, which has usually low throughput and is therefore impractical for large-scale manufacturing. Therefore, we studied the mass production techniques and related theory for fabricating2D nanochannels with low cost and high-precision. The main research work of this dissertation is summarized as follows:First, a novel method based on low temperature sidewall technique for fabrication of2D silicon nano-mold is presented. A nano-thick layer of Au film is first sputtered onto the surface of the micro-sized photoresist mesas formed by conventional ultraviolet (UV) optical lithography. Then, arrays of one-dimensional (1D) Au nano-sidewalls are formed by anisotropic sputter etching. By taking the1D Au nano-sidewalls as a mask, the2D silicon nano-mold is obtained by Deep Reactive Ion Etching (DRIE) process.We analyze the effects of process parameters on the2D nano-mold fabrication resolution. As compared to other sidewall technologies (with process temperature more than300℃), the entire process of the presented method is performed under a relatively low temperature environment which is below40℃. Thus, lower thermal stress is generated which improves the bonding strength between the sidewall and substrate. This method does not require expensive equipment such as electron beam or focused ion beam lithography. It can provide support for production of high-precision2D silicon nano-mold with low-cost and large area.Second, the2D nanochannel fabrication method is studied based on the hot embossing technique. We assume that the substrate area of the polymer is not constant during the hot embossing process. A thermoplastic polymer compressive creep model is derived from the viscoelastic creep constitutive equation. Influence of embossing temperature, embossing pressure, and embossing time on replication resolution of2D nanochannels is studied by numerical simulations and experiments and the process parameters for fabrication of2D nanochannels are optimized. Thus, high quality polymer2D nanochannels can be obtained by replicating the features of the2D nano-mold into the polymer substrate with the optimized process parameters. Third, an oxygen plasma assisted thermal bonding technique is studied for sealing the2D nanochannels. The effctive bonding area, bonding strength, and deformation of the2D polymer nanochannels are selected as the evaluation indexes, and the effect of bonding temperature, bonding pressure and bonding time on the bonding quality of polymer2D nanochannels are studied and optimized. Finally, the enclosed2D nanochannels with low deformation loss and high bonding strength are obtained without clogging and leakages. High-precision2D polymer nanochannels are fabricated by using this method.In this thesis, a novel method for fabrication of2D polymer nanochannels with low-cost and large area is proposed based on experimental analysis and theoretical study. This work can provide important support for practical applications of2D nanofluidic chips.