Integrated Raman Spectrometers for applications in Health and Medicine
Promotion date: 8. February 2012
Promotor: Prof. dr. Markus Pollnau, Prof. dr. Alfred Driessen
Assistant promotor: Dr. ir. René M. de Ridder
Recent advances in solid-state lasers and high resolution charge-coupled devices have allowed Raman spectroscopy to emerge as a powerful tool in many applications, as for example in the fields of virology, pharmacology, forensic science, cosmetics, bioscience and nanotechnology. The goal of this research is to contribute even more to the widespread of this technology by developing low-cost, portable Raman spectrometers, integrated on a chip. In particular the project aims at the fabrication of on-chip devices to be used for the detection of Raman signals from biological samples such as human skin and teeth.
Such spectrometer systems comprise optics for delivering an excitation laser signal to, and collecting the resulting Raman signal from the specimen; a laser line filter; a laser suppression filter; the Raman spectrometer; and, for some applications, polarization splitters.
In the course of the research a novel device for laser delivery and confocal signal collection is developed, that may open the doors to new types of applications in the fields of microscopy and spectroscopy, for example in combination with microfluidics.
We also proposed a novel design for the Arrayed Waveguide Gratings which appears to be advantageous especially when high diffraction orders are required.
We have also successfully demonstrated Raman spectroscopy from human tissue (in particular teeth) by using on-chip AWG spectrometers.
Was your research application driven or were fundamental questions also important?
Raman spectroscopy is available in many medical applications already. The equipment however is very expensive. We searched making integration on one chip possible and integrated all functionalities on one chip. Then, hopefully, in future Raman spectroscopy is usable in developing countries and also for a wider range of applications; not only in hospitals but also at other locations, for example at the sea-side for early detection of sunburn or other skin related deceases.
Especially the spectrometers were part of my job, to design and to characterize them. The chip-devices are some centimetres large, however their wavelength resolution is in the order of a fraction of a nanometer. Also filters, signal collection and laser delivery devices were part of my investigations, leaving out detection devices and light sources. Here, a lot of work still has to be done.
For example I designed special filters that had to strongly suppress the excitation wavelength and at the same time allow the weak Raman signals to pass through.
So, it was a multidisciplinary project.
Yes, very much so. Coming to a portable device for Raman spectroscopy is a challenging piece of engineering involving companies like Lionix in Enschede , 2M Engineering in Veldhoven and River Diagnostics in Rotterdam. Also the Laser Group in Delft and the National Research Centre in Canada were involved. They are experts on teeth research. They delivered samples in trying to find caries at early stages.
Overseeing the project as a whole is important in a complex project like this. Also there was a patent procedure involved, regarding the laser delivery (to the sample) and signal collection only using on-chip technology. I learned a lot by following the steps of this procedure and by using my soft skills selling the patent to future clients. It takes courage and real belief in the technology.
What are your future plans?
At the moment I am working on a post-doc project for one year on Optical Coherence Tomography. After that the choice for continuing academic research or switching to research in industry will be a difficult one for me. Although I like the application-oriented research and product development, also the amazing and free academic research is appealing to me. As my family is living here, I like to stay in Holland anyway.
What in your opinion is important for Mesa+ to stay successful in future?
The Mesa+ days I liked very much. Also the monthly colloquia were interesting, especially if the topics were somehow related to my own research.
I guess, the technical colloquia are really important to learn which research facilities are present at Mesa+ and available for performing any type of measurements. In this way one can come to new ideas for his own research ends.
The apparatus of Mesa+ is of world class level, especially as the new cleanroom capacity is coming to full speed now. Maintaining the equipment and keep the apparatus working is important for the researchers to quickly perform high-quality measurements and experiments.