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In Yee Phang (promotion date: 24 October 2008)

Marine bio-fouling surfaces: morphology and nanomechanics of barnacle cyprid larva adhesion proteins by AFM

Promotion date: 24. October 2008

Thesis advisor: Prof. Dr. G. Julius Vansco

In the barnacle’s cyprid larva stage, barnacles move to settle themselves on a hard marine underwater surface, f.e. a ship hull. The footprints they produce attract other barnacles and encourage them to colonize together. Using AFM-techniques the structure, mechanical properties and characteristics of the cyprid larva stage, are studied.

Do these barnacles cause big problems?

Yes, they do. If only five percent of the surface of a large ship, for example three hundred meters long, is colonized by barnacles, the extra fuel consumption can reach millions of dollar per annum. This is also really bad for the environment, considering raising exhaust rates of carbon dioxide and other gasses. Therefore the Dutch Polymer Institute funded this project.

What was your strategy, and in what way was nanotechnology involved in this specialized subject?

In the cyprid larva stage (baby stage) of the barnacle, they search the underwater structure in order to find a stable spot to settle for survival. By making use of the atomic force microscope I concentrated on the porous and thin layer of the footprints, i.e. 30-50 micrometer in diameter and 50 nanometer thickness, the barnacles leave behind.

Because the footprint is a very thin layer and a tiny amount of macro-molecules is involved, the AFM is a very powerful instrument to study the nano-mechanical properties, especially for this kind of biological data in its native form.

There is no need to dry the sample. With this ability, I was able to investigate the footprint proteins with which they attach themselves to the surface. These appeared to be rather tough. Together with the hairy ultra-structure in the attachment organ, cyprid larva can attach tenaciously underwater.

I went to Singapore twice to collaborate with biologist colleagues there. We carefully prepared samples and put them in the sea to obtain realistic circumstances, and compared the results from the laboratory settlement assay and the AFM morphology studied.

Did you do some recommendations?

In one of the chapters I discuss a method to use enzymes that can remove the footprints. It can protect the surface and minimize problems from the very beginning, rather than killing the settled adult barnacle. If these footprints can be wiped out, the risk of big colonies of barnacles to settle is reduced.

How did you come into contact with this project?

During my master in Singapore, I met Professor Julius Vansco. I knew he was from MESA+. The group Materials Science and Technology of Polymers I found very interesting, and the project using the AFM was a big challenge.

What are your future plan?

The next six months, I will perform a post-doc at MESA+, that is also AFM-related. It is about measuring nanoparticles that are “hidden” in polymers. Using the combined setup of ellipsometry and AFM we can go beyond the limits of optical microscopy, by using no lenses at all.

After that, me and my wife - who also finished her promotion project at MESA+ on the same date I did – are looking for other jobs. That can be all over the world, really. I prefer a research related position, because I like the freedom of working in this way. And it satisfies my curiosity.

Being a researcher involves a combination of patience and passion. F.e. looking for barnacle footprints and make meaningful measurements out of them, did cost me nearly two years. But the result is ever so rewarding.

What does MESA+ need to stay successful in the future, you think?

First of all, they should maintain the open and international oriented structure, I believe. But also, I think, more Dutch students should perform top-research jobs at MESA+. The government should do extra effort to encourage high-potential Dutch students to come working for MESA+. In that way you enhance quality and that will attract other top-notch candidates. Stop investing in quality research has the danger that it would break down this successful system, that is built up in a long period of years.