Fabrication of inorganic-organic hybrid polymer micro and nanostructures for fluidic applications

Abstract

Microfluidics is a rapidly developing branch of microtechnology with applications in chemistry, biology, medicine and other sciences. One major trend in fluidics has been the miniaturization of analytical devices. Miniaturization improves performance, mainly speed and sensitivity, and also reduces the required sample volumes. Initially microfluidic devices were fabricated from silicon and glass using microfabrication methods borrowed from the integrated circuits industry. But polymers are gaining more and more attention due to their simple processing and potential of being so inexpensive as to be disposable. Many different polymer materials have been used, including polydimethylsiloxane (PDMS), polymethyl methacrylate (PMMA) and epoxy-based SU-8. Although these polymers have proven to be useful in some applications, there is still need for easily processable materials that would have the chemical tolerance and favorable surface properties for analytical applications. One such major issue is avoidance of analyte adsorption on chip walls in separation devices. In this thesis, a new materials class, ORMOCER©s, are introduced into microfludics. Ormocers are inorganic-organic hybrid polymers that combine the beneficial properties of organic materials and glass/ceramics. They can be cured by using UV-light, like negative photoresists, and their surface properties resemble that of glass. New UV-embossing techniques have been conceived and tested for Ormocer patterning in this thesis. Combined with a novel self-adhesive bonding process, devices made of 100% Ormocer have been realized for the first time. Fabrication of Ormocer structures by embossing and bonding is fast and simple compared with many other polymers, and significantly easier than silicon or glass processing. Due to its unique chemical composition, nanopores can be formed in Ormocer by etching the organic sidegroups away in oxygen plasma. The microchips produced in Ormocer have been used in applications like capillary electrophoresis (CE), integrated capillary electrophoresis and electrospray ionization (ESI), and as substrates for surface assisted laser desorption ionization (SALDI). Ormocer has proven to be highly successful in these analytical applications. Especially intriguing is the excellent CE separation performance for peptides and proteins which is explained to be due to inherent resistance of Ormocer against analyte adsorption.