Abstract by Nan Lu

Micro total analysis systems (μTAS) have great potential for chemical and biological platforms. The miniaturized analytical systems are favorable in handling minimal amounts of sample and reducing regent consumption. They are cost-effective compared to more traditional instrumentation, provide ease of automation, and are capable of integrating different processing units into a single device. Traditional materials for fabricating microdevices, such as glass and silicon, require costly and labor-intensive procedures. Thiol-ene polymer is considered as an attractive alternative material for microscale systems, not least because of its amenability to economic as well as mass production, and its unique polymerization characteristics.

The overall aim of the current Ph.D. thesis was to explore the potential of thiol-ene polymers for the fabrication of miniaturized platforms for bioanalysis. The development of two microdevices will be presented, both having an electrophoretic separation mode as its core functionality, but with different pre- or post-separation units added.

The first part presents the development and application of a free-flow electrophoresis microfluidic chip, and its upstream combination with an enzyme microreactor with immobilized pepsin in the same miniaturized platform. It extends the application of μFFE and could be considered a potential tool for online chip-based peptide analysis. The continuous separation approach also allows for collection of larger amounts of analytes, improving in particular mass-dependent detection.

Non-aqueous capillary electrophoresis (NACE) on microfluidic chips is still a comparatively little explored area, despite the inherent advantages of this technique and its application potential for, in particular, lipophilic compounds. A main reason is probably the fact that implementation of NACE on microchips largely precluded the use of polymeric substrate materials. Here, we report non-aqueous electrophoresis on a thiol-ene-based microfluidic chip coupled to mass spectrometry via an on-chip ESI interface.

The supplementary part discusses the integration of on-chip H295R cell cultures with enantioselective separation of chiral fungicides on a thiol-ene based microfluidic platforms.

Overall, the presented thesis shows the feasibility of thiol-ene materials for the development of microfluidic chips with multifunctional elements. The rapid prototyping, tunable and versatile surface chemistry, and high resistance to solvents for thiol-ene, allows for the large-scale production of microdevices and extends the application of this material to microscale analytical purposes.