Advanced three-dimensional lab-on-a-chip architectures for integrated surface-enhanced Raman spectroscopy (LoC-SERS)

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Lab-on-a-chip surface-enhanced Raman spectroscopy (SERS) is a very promising method for sensitive biochemical detection of low-concentrated analyte in water. However, two issues should be addressed. First, low-cost fabrication of on-chip-integrated SERS nanostructures with high reproducibility in enhancement factor is still vacant. Second, an on-chip-integrated laser excitation source, especially a spectrally tunable laser source, is still missing for this application. This proposal suggests an interdisciplinary approach, combining micro-/nano-systems engineering and nanophotonics for surface-enhanced Raman spectroscopy applications. The main objective of the project is the technical realization of a Raman-on-chip optofluidic platform with integrated organic semiconductor lasers. Furthermore we aim at a fundamental understanding and an optimization of localized surface plasmon resonances (LSPR) for SERS applications using low-cost metal-organic hybrid nanostructure arrays. Our work will mainly address the following issues: 1.) Using laser-assisted hot embossing, the process for defining periodic nanopatterns into polymeric substrate will be explored. The Raman enhancement factor of metal-organic hybrid nano-patterns will be experimentally characterized on non-integrated SERS substrates. 2.) Periodic nanopatterns in various geometries will be investigated using finite-difference-time-domain (FDTD) modeling simulations, aiming to improve the SERS enhancement factor at different excitation wavelengths for biochemical analysis. A close feedback loop with the experimental work will be maintained. 3.) The optimized nanopatterns will be integrated into the microfluidic channels on a polymeric chip. As a further step of integration, organic semiconductor distributed feedback (DFB) lasers will be introduced onto the chip using a combination of laser-assisted replication and ink-jet printing. The SERS chip will be finalized after the encapsulation with a polymeric lid, which will be achieved by laser transmission welding. 4.) SERS excitation using an organic DFB laser will be realized in the first way by introducing external optical elements, e.g., commercial available off-axis parabolic mirrors. In the second way, a functional polymeric lid which comprises integrated optical components is to achieve a perpendicular laser excitation on SERS-analysis fields. The geometry and tolerance of integrated mirrors will be investigated using systematic optics design. The encapsulation process will be achieved by laser transmission welding with high precision in positioning. 5.) Finally we will perform first biochemical tests based our fabricated SERS-nanopatterns and LOC-SERS chips. Therefore we aim at demonstrating on-site inline water quality monitoring and moreover biomedical diagnostics of cancer-specific mutations in the oncogene of the peptide.