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Sertan Sukas (promotion date: 15 February 2013)

Microchip capillary electrochromatography with pillar columns

Promotion date: February 15

Promotor: Prof.dr. Han Gardeniers

Novel methods for microchip capillary electrochromatography applications with micro fabricated pillar columns were investigated in a systematic way.

The first goal was to make the best column design ever. Computational models were constructed to design and optimize the pillar shapes instead of fabricating and experimenting the outcome of the incremental design changes. The resulting shape – using the cross section of an airplane wing as a design base - and placement of the columns, were compared with the ones from literature. The proposed designs yielded a superior performance "on paper".

Microchips were fabricated and tested under both non-retained and retained conditions. Experimental results showed that the foil shape performed the best in all working conditions in "real life".

Also an optimized distributor structure was designed for the electro-kinetic injection by means of computational modelling. An extra advantage of the optimized injector was the ability of controlling the injected sample volume precisely.

The most important application related issue for solid pillars, appeared to be the load ability problem. The only way to increase the volume and the surface at the same time, was deploying porous layers over the pillars. The substrate material changed to silicon (from fused silica). It was anodized to obtain a porous silicon layer over the pillars, and the porous silicon layer was converted into porous glass with an insulating solid silica layer underneath, using thermal oxidation.

Were there some special moments that you recall during your thesis project?

I had two papers published: one concerning more the theoretical part of my work, in Electrophoresis Journal, the other being more on the experimentation and implementation part, in Analytic Chemistry. Two more manuscripts on the injector design and the integrated porous silica fabrication, were submitted to the Journal of Chromatography and Lab on a Chip, respectively.

Beforehand I was very curious how people would react on my findings. By receiving such great comments, especially form the reviewers of Analytic Chemistry, I was strengthened in my belief that I did the right thing in focussing on this subject and this approach. Normally I am not a highly emotional type of person, but this time was somewhat of an exception to that.

In what way did you develop personally, as a scientist and researcher?

During my master thesis, I was more likely to solve problems from an engineering perspective This suited my personal perception being more of a technician myself than a scientist.

During my PhD thesis, I spent much more time in understanding the physics of the problem in a thorough way. Working on modelling guided the experiments, knowing beforehand what results were realistic to expect.

Scientific research is a right cycle of: theoretical approach, model verification and getting result from experiments. In that way one can work towards optimization. This is especially important in my area of research, even necessary, in field fluidics. The optimization of the shape and the placement of the pillars, serves as a prove of that. In this way one can gain improvements on the timing of the separation process – taking place earlier - resulting in narrow and sharp detection bands.

Are your findings close to application?

The area of research certainly is. Our research fellows at the University of Brussels are close to the market with a similar pressure driven application device. They started earlier on that.

My approach can be optimized further. Using polymer instead of silica is a commercially exciting option, for example.

What are your future plans?

Right now, I am working as a post-doc in the BIOS Lab-on-a-Chip group of research which is part of Mesa+. I am planning to apply for a Veni-grant taking my idea further. Also, I am planning to start a spin-off company in order to realize the commercial value of a new kind of microfluidic device.

This is a fascinating route. Of course, I can fail much more easily than working safely in a proper job. On the other hand I am sure to have double fun in pursuing my goals. In Holland the opportunities to do so are favourable as compared to my home country of Turkey. In science however, one is working for a public that can be anywhere, so the exact working location is of minor importance.

What, in your opinion, is important for Mesa+ to stay successful in future?

I guess, in some areas Mesa+ can save some costs, for example by using costly equipment to fabricate nanostructures in exotic ways. By attracting experienced colleagues who are aware of the possibilities and usefulness of producing experimental devices, research can be carried out more effectively.

On the other hand, the equipment available here at Mesa+ is outstanding. So, also investments should continue.

Mesa must try and stay in touch with colleagues, politicians and the public. This also is of prime importance, I believe.