Towards labonachip optical trapping and Raman spectroscopy of extracellular vesicles using multiwaveguide traps
G.B. Loozen (TU Delft - ImPhys/Computational Imaging)
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Abstract
Optofluidic lab-on-a-chips (LOCs) employing a dual-waveguide trap for optical trapping and Raman spectroscopy have proven to be attractive and potent tools for high throughput chemical fingerprinting of bio-particles for disease diagnosis. Among the relevant bio-particles are extracellular vesicles (EVs) which a been proven through recent studies to be potential biomarkers for identification of diseases, such as cancer. However, EVs are small with diameters ranging between 30 and 1000 nm and present a challenge for both on-chip optical trapping and Raman Spectroscopy. The research presented in this thesis is aimed at the development of a multi-waveguide optical trap aimed at the combined on-chip optical trapping and Raman spectroscopy for biochemical characterisation of single EVs.
Firstly, the capabilities and limitations of a dual-waveguide trap for stable on-chip optical trapping of EVs is investigated through an in-depth simulation study. This ultimately yields a comprehensive overview of stable trapping conditions for EVs in terms of EV diameter and refractive index, and the injected optical power.
Then, novel multi-waveguide traps are designed and fabricated. These multi-waveguide traps lead to stronger light confinement in the channel, resulting in improved optical trapping and Raman signal generation. This is experimentally demonstrated through the optical trap stiffness values and the recorded Raman signal strength of polystyrene beads generated between a 2-waveguide and 16-waveguide trap.
Finally, the 16-waveguide trap is used to demonstrate optical trapping of B. Subtillis spores, as an intermediate step towards EVs. Optical trapping of the spores is studied with both experiments and simulations. Special attention is paid to the effect of random phase differences between the beams exiting the waveguides on the optical trap quality.
In conclusion, the results show promising prospects for the realisation of multi-waveguide traps for on-chip biochemical fingerprinting of EVs with optical trapping and Raman spectroscopy.