Improving robustness and disposability of integrated Young interferometer sensors for portable diagnostics: Dissertation

Integrated Young interferometers (YIs) are label-free photonic sensors having many desirable features for point-of-need diagnostics. They have been shown to be sensitive, they are capable of multi-analyte detection, and they can be implemented using low-cost polymeric materials. However, there are also some disadvantages from the low-cost portable diagnostics point of view: sensor readout is easily disrupted by mechanical disturbances, and the realization of disposable photonic sensor chips for cost-critical applications using established batch-based processes is difficult. The objective of the work discussed in this thesis was to improve the applicability of integrated Young interferometer sensors for low-cost portable diagnostics by means of two themes: improving the robustness of the sensing method against mechanical disturbances and improving the disposability of the sensor chips. To improve the robustness, a drift compensation method was derived. The method was shown to be able to extract sample-induced phase change responses from up to 161 times larger phase changes measured with a deliberately mechanically disturbed setup. Disposability was improved by demonstrating that YI sensor chips can be implemented using polymeric waveguides manufactured by ultra-high volume roll-to-roll (R2R) methods. Three sensor embodiments were designed: one for ambient refractive index sensing, one for sensing of small molecules, and one for multi-analyte detection of biomolecules. In the experiments, ambient refractive index changes were detected at a level of 10-6 refractive index units. Analytespecific sensing of small molecules was demonstrated using a sensor chip functionalized with a molecularly imprinted polymer. For multi-analyte detection of biomolecules, sensor chips were functionalized with inkjet-printed antibody layers. Improving the robustness of the sensing method and proving the concept of disposable photonic sensor chips opens up new possibilities to implement lowcost portable sensor systems.