Year: 2007
Type: dissertation
Abstract: Miniaturization of analytical devices has been an ongoing trend to improve performance of analytical tools. These systems have been microfabricated originally of silicon and glass, but polymers have become increasingly popular as alternative materials. Polymers are mostly used because the material costs are lower and fabrication processes are easier. However, those facts depend heavily on the fabrication method and particular polymer. In this thesis the usability of epoxy-polymer SU-8 has been studied for analytical microfluidic applications. Lithographically defined SU-8 can provide simpler fabrication processes as comparison to silicon and glass fabrication. In this thesis processes for microdevice fabrication of SU-8 are studied and developed. For many devices the proper microchannel enclosure method becomes the most critical fabrication step. Therefore adhesive bonding using SU-8 has been studied extensively.\n\nA widely applicable microchannel fabrication process has been developed as a combination of lithographic patterning of SU-8 and ultraviolet-cured adhesive bonding. This process enables high yield of microfluidic devices with wide range of channel dimensions both laterally and cross-sectionally. Furthermore, multilevel structures are possible, inlet fabrication is easy and alignment of inlets and other structures like electrodes can be done fully lithographically. Hence the SU-8 fabrication process avoids many limitations of the earlier fluidic chip fabrication processes.\n\nSU-8 microchannels have been used for electrophoretic applications for the very first time. Electroosmotic flow (EOF) mobility was measured in the channels and also first electrophoretic separations were made. SU-8 promises good properties for such applications, because the EOF mobility was higher than with most other untreated polymers. Solid phase extraction was integrated to electrophoresis chips to enable sample purification or concentration before the electrophoretic separation. This was realized by applying high aspect ratio pillars and multilevel SU-8 structures. Detection from the chip can be done by fluorescence detection through the SU-8 cover. To improve detection sensitivity mass spectrometric detection was also studied from the chips using electrospray ionization (ESI) mass spectrometry. SU-8 provided good material properties for the ESI-analysis. Furthermore, SU-8 enables accurate tip fabrication that is difficult with most other microfabrication methods.
Source: Aaltodoc (Aalto University)
Author: Santeri Tuomikoski
Institution: Aalto University
Language: English
Subfield: Biomedical Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W2596012525