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Joris van Lith (promotion date: 2 February 2005)

Integrated optical sensing platforms for chemical and immuno-sensing

Promotion Date: 2 February 2005

Joris van Lith

My research was about the development of a specific type of sensor: an integrated optical sensor. These sensors are developed on optical chips making use of the properties of light instead of electrical currents. The microscale of these chips opens up a range of possibilities that are unthinkable with for instance the manipulation of light with lenses, for on this very small scale the conventional laws of light (light as a beam) are no longer valid. We are talking about light now as a field with a certain intensity distribution. Interpretation of these intensities allow the development of highly sensitive sensors.

What was your thesis about?

My research was about the development of a specific type of sensor: an integrated optical sensor. These sensors are developed on optical chips making use of the properties of light instead of electrical currents. The microscale of these chips opens up a range of possibilities that are unthinkable with for instance the manipulation of light with lenses, for on this very small scale the conventional laws of light (light as a beam) are no longer valid. We are talking about light now as a field with a certain intensity distribution. Interpretation of these intensities allow the development of highly sensitive sensors. These sensors may be either chemical (for the detection of chemical concentration in a variety of substances) or biological, e.g. for the detection of antigens called immuno-sensing.

There is a lot of research going on in immuno-sensing. Why ?

A hot issue at the moment is the detection of ‘bio-terrorist threats’. This is one of the reasons why for instance the US are spending such huge amounts on this kind of research.

Medical applications are another very important application area. Existing sensors detect dangerous chemicals, bacteria or viruses in the air with antibodies that have fluorescent properties when bound to an antigen. This is an extremely sensitive method, but you need chemicals in bottles for it. If you could have an integrated optical method, the labelling of fluorescent molecules is no longer necessary and with these you could continuously and cheaply ‘sniff’ the air around you. At the moment in all Undergrounds in the US you will find huge sensor cases for the detection of poison gases and bacteria. But these sensors need a lot of tubes and chemicals, they do sometimes leak etcetera. A small sensor on a chip would be much easier.

What was exactly new about your project?

The whole area is still pretty innovative. Because it is relatively new, there are a lot of sensors that have not been developed yet. I researched and developed two completely new principles: one included in the project proposal and one entirely of my own. I also theoretically described three other principles.

So in fact you did more than was expected?

Yes and no. For the sensor described in the project proposal we were to develop a proto type of a micro sensor to detect fog, but it turned out that the gelatine –the sensing material- used to make this sensor was not at all suitable for the purpose. Also the immuno-sensing for anti bodies did not lead to direct results, because we did not have the specific expertise in our group. But on the whole I have very good specific results, I think, although we did not go quite the way that was thought up at the beginning of the project.

How do financers and committees react to that?

Well, every half year you have meetings and discussions about the project’s progress. So of course it does not come to them as a complete surprise. They know what we are doing and if that presents a problem for them, they would have let us know. The company that wanted commercially produce the air humidity sensor was of course disappointed, but a negative outcome is also an outcome: this kind of sensor is not suitable for fog detection. That also is worth knowing.

What did you like best about your research?

The research in itself. The challenge of it; to continually overcome the problems that occur.

Any setbacks?

Also for me the realization that the air humidity micro sensor was not going to work was a disappointment. Because in science if something does work, you can write publications and everybody sits up and takes notice, whereas with a negative result, -useful as it may be-, there are no publications and congresses to go to. So that is why I started to develop the ideas of my own which I described theoretically. And these are the results that we will publish eventually.

What are your plans?

I found a job in New Zealand with a company for nano electronics. So I will move to Christchurch. I have a two years’ contract. I will work with sensors again, on a nano scale.

I am looking forward to that, and to life in New Zealand.

For the summary of the thesis, click here.