SERS sensors for DVD platform

This Ph.D. thesis explores the engineering of a portable sensor system for detection of rare and small molecules. The Ph.D. project is part of the research project 'Multi-Sensor DVD platform' (MUSE), aiming to integrate different sensors on a rotating disc. The sensors are chosen to complement each other, creating more reliable and stable results for the end user. The rotating disc comprises microfluidic channels, which can be utilized for handling and manipulating liquid samples such as blood or water. The focus of this Ph.D. thesis, is on the integration of one specific sensor on a rotating disc. The sensor is based upon surface enhanced Raman spectroscopy (SERS), which detects molecular vibrations. The aim of this thesis is to cover the different aspects of the sensor system.
SERS substrates, consisting of nanopillars with gold or silver caps on top, have been fabricated by standard micro and nano fabrication techniques. These substrates possess plasmonic properties and can therefore enhance Raman signals from even small molecules in close proximity to the surface of the caps. By introducing high temperature annealing to the fabrication process, the SERS background signal, originating from etch residues, has been reduced, further improving the SERS signal.
Microuidic sample handling are, in combination with the SERS sensor, to be used with the DVD system. Nanoparticles has been investigated as a mean to capture and handle the target molecules. This enables the use of sandwich assays between the substrate and nanoparticles for biodetection. It is demonstrated that the SERS substrate maintains its enhancing properties when the nanoparticles are immobilized on the surface.
By introducing a dynamic measuring method called DynaSERS it is demonstrated how the stability of the Raman signal can be improved. Additionally, the assignment of vibrational modes is made easier, as the peak width is reduced and the peak position is shifted.
Finally, the instrumentation for a portable sensor system has been investigated and SERS measurements on a rotating microfluidic disc has been demonstrated.