One-dimensional confinement of colloids and light by hydrodynamic flow focusing

Abstract

In this thesis, we studied on the one-dimensional (1-D) confinement of colloids and light by hydrodynamic flow focusing. The 1-D confinement of colloids could be achieved using the fiber, which was generated by the electrohydrodynamic flow focusing known as electrospinning, as a confined geometry. As the electrospun fiber was extended highly, the colloids dispersed in the polymer solution began to assemble spontaneously into a pearl-necklace structure. The fabrication of multilayer polydimethylsiloxane (PDMS) microfluidic system was also examined. Stable stratified liquid stream could be generated by the hydrodynamic flow focusing using the PDMS microfluidic devices. 1-D confinement of light could be achieved by total internal reflection in the stable stratified liquid stream. Optofluidic waveguides with large captured fraction and low propagation loss could be prepared using the 1-D confinement of light. Monte Carlo simulation method was developed to calculate the captured fraction of the fluorescent optofluidic waveguides. Evanescent wave coupling-based optofluidic sensor was also studied by coupling two different wavelength of light into the optofluidic waveguides. Meanwhile, real time detection of droplet in microfluidic device was studied using integrated optics. Finally, we investigated the pneumatic control of optofluidic waveguides toward optofluidic switch by using the multilayer PDMS microfluidic systems.