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Rerngchai Arayanarakool (promotion date: 18 October 2012)

Single-molecular analysis on droplet-based multiphase microfluidic systems

Promotion date: 18. October

Promotor: Prof. dr. ir. Albert van den Berg

The main objective of this thesis was to develop a micro- and nanofluidic platform for the generation and manipulation of tiny (femtolitre) aqueous droplets in the oil phase (water-in-oil emulsion), for the encapsulation of a single molecule of enzyme to perform an enzyme kinetic analysis.

A plenty of tiny droplets (f ~2.5-3 mm) generated from this fluidic system, were highly monodisperse, beneficial for the usage of the carriers for an analysis of single enzyme activity. To avoid high background noise, the enzyme and substrate solution was confined into femtolitre carriers, achieving high product concentrations from single-molecule encapsulation.

The method presented here allows to follow large numbers of individual droplets over time. The instrumental requirements are furthermore modest, since the small droplet size allows the use of standard microscope and standard Pyrex glass chips, as well as the use of relatively high enzyme concentrations (nM range) for single molecule encapsulation.

Was your research application driven?

Applications are to be found in the design of new laboratory apparatus for biology research. The method of encapsulating solutions of enzymes in oil, and performing on them measurements on a molecular basis, is advantageous. It delivers individual information rather than being forced to average over millions of enzyme molecules. Also the encapsulated enzymes are more realistic, almost like actually ‘living’ inside a cell.

The research was funded by the European Research Council (ERC). Collaboration was there with the Wageningen University.

In what way did you develop as a researcher and scientist during the PhD period?

First of all, now I am working much more systematically. So my method of research is much more structured now.

Also as a scientist I grew considerably. For example, when things happen during experiments I didn’t expect at all, I learned to look at these phenomena in a broader perspective, viewing them as part of a bigger picture. For example we found some phenomena in the water-oil phase that were not expected but which fitted in very well within the application scope of labs-on-a-chip and also in other research tools.

Also I learned to explain all the relevant phenomena taking place. This is a complex skill one has to learn before becoming a successful scientist.

Did you manage to have nice publications?

Yes, I published two times in Lab-on-a-Chip Journal. One article is underway still. Also I had poster presentations all over the world: in Holland, Switzerland, USA and in Japan soon.

What are your future plans?

Now, I am going to work at the IFW Dresden. During my post-doc, I would like to add to my skills on micro and nano fluidic technology in combination with biological aspects. In my view these skills are of major importance in order to find new ways of designing medicines. That is why biology is so important in this kind of nano-research. Biology is all about life. Facilitating lab research or helping out on new direct applications are important fields of research.

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

Within Mesa+ a lot of research groups are there, collaborating on various subjects. Together with the research, lab and cleanroom facilities, this is important to hold on to.

The freedom of research I experienced, is very fruitful in my opinion. My supervisor gave me guidance and made some important decisions along the way. Within this process I was able to express many new ideas of my own. That was very inspiring.