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Heiko van der Linden (promotion date: 19 November 2003)

Investigation of the potentials of stimulus-sensitive hydrogels for micro actuator applications

Promotion Date: 19 November 2003

Heiko van der Linden

It is a new principle for a bio pump really. My professor was involved in analyses of blood samples on the body itself using biosensors. A chip with a minute little pump sucks a bit of blood along sensors, measuring for instance blood sugar. We made an inventory of the existing systems, which all had specific setbacks that were mostly dealing with size.

What was your thesis about?

It is a new principle for a bio pump really. My professor was involved in analyses of blood samples on the body itself using biosensors. A chip with a minute little pump sucks a bit of blood along sensors, measuring for instance blood sugar. We made an inventory of the existing systems, which all had specific setbacks that were mostly dealing with size. Because no system was really satisfactory, we thought of the application of a new principle: the stimulus sensitive hydrogel, which is a polymer absorbing water. If you change the PH of the polymer by electrical current -needing only a very small battery- it either shrinks or expands. This principle we wanted to apply to our micro pump.

I also had to put in a lot of research into the actual hydrogel, because it did not exist in such an extremely small size. Also the division between the gel itself and the to be pumped fluids took quite some effort. We succeeded, but one problem remained: the expansion is very slow. Up to two hours even. We proved that everything works but did not get round to actualization of the material.

Is it possible to find a material that is quicker?

It must be further investigated. There are a number of properties with which you could speed up the process. There are also a number of gels that react to temperature, which is much quicker.

Is the application of this principle purely medical?

No, it could be anything. Because of the separation of gel and fluid, you could pump a variety of substances, ether or petrol or gasses. This was not possible before.

Was it a disappointment that the pump was so slow?

Only in the beginning I thought of it in terms of disappointment. You could say that I did not reach the ultimate goal: making the pump to work in practice. On the other hand, we made enormous progress in the field of characterizing the materials as well as the gels.

It has never been done before that the specific characteristics of these polymers are being put to practice.

Did you work with other groups?

At the beginning with the Polymer Group here at Mesa+ and later I went to America for three months. There was a group working with these materials as well. But the field is so new that this did not actually contributed a lot.

Did you enjoy being in front of the troops, so to speak?

Well, sometimes you have your doubts. Will it ever work? What I found is that you must get a grip on every aspect. Nothing can be neglected, every small detail needs to be investigated.

Where did the idea come from that the characteristics of these polymers could be used as a pump?

My professor thought of this, made a project and looked for somebody with my background, which is pharmacy, chemistry (organic synthesis) and I am an electronics enthusiast besides.

Because of my electrical engineering skills the lack of mathematical background was generously overlooked. I am pleased that I did not betray this confidence and succeeded in this very challenging project. It was a great opportunity for me to study a completely new principle, to look at the micro system side of things and to work in the clean room.

It was great too, that I got so much of a free hand.

What are you going to do next?

I now have a postdoc position at Groningen University, because a lot of interesting angles for further research have presented themselves from a pharmaceutical point of view. I want to look into an antigen sensor in Groningen. In the field of antigen detection my experience with micro systems is very useful. It is also a starting group with plenty of challenges. The pharmaceutical industry is a good line of business besides. Nobody is cutting costs where health is concerned.

So you will eventually make the switch from science to industry?

I don’t know yet. But when I see how hard my professors have to work and are more or less sacrificing there private lives for their careers, I do have serious doubts, especially since a lot of their workload has nothing to do with their scientific interests. Nearly half of their enormous effort is taken up by writing applications for funding, supervising students, management tasks, practising presentation skills, etcetera, etcetera.

That is all very different in America. If doing the things I want to do are getting too difficult here, I will go there. Or to New Zealand. Or Switzerland.

With the background I acquired and with the ability to persevere that I got along the way,

I could go anywhere.