Thijs van Leest

In my PhD project I mainly work on on-chip optical trapping devices, designed for trapping single bacteria in water. The goal of this Wetsus project is to investigate the feasibility of an on-line lab-on-a-chip sensor for detecting single bacteria in drinking or surface water, by combining Raman spectroscopy and trapping for the identification of hazardous bacteria. Photonic crystal cavities are designed and optimized using computational tools and fabricated using nano-lithography and microfluidic techniques. Experiments have demonstrated that the various devices developed are very suitable for optical trapping and that two-dimensional photonic crystals form a very interesting novel platform for optical manipulation in general.

This thesis presents a lab-on-a-chip approach for single-cell optical trapping sites based on photonic crystals, in which optical resonators at the wavelength scale are created. The small footprint of the resonator, combined with microfluidic and photonic techniques for transporting single cells to sensing sites, potentially allows vast parallelization on a single chip, thereby speeding up sensing for high-throughput monitoring with single-cell precision. The resonators and other on-chip optical manipulation devices have been optimized, fabricated and experiments have confirmed that bacteria can be trapped and manipulated. Besides Raman sensing, the techniques developed are promising tools applicable to single cell research, transformation and nanoparticle assembly.