Düzlemsel genişlemeli akış içinde hidrodinamik tuzaklanmış mikrodamlaların ışıması ve çözülmesi

Dissolution of one phase into an immiscible phase is of great importance to food and drug industry. Dissolution process is mainly affected by diffusion coefficient, solubility, density and viscosity of the dissolving material in the immiscible phase. This thesis reports dye lasing in hydrodynamically manipulated microdroplets and proposes the hydrodynamic trap as a new method to observe dissolution of microdroplets. In the first part of this thesis, utilizing previously available hydrodynamic trapping method, we trap and manipulate the position of a dye doped liquid microdroplets in a microfluidic chip. By manipulating the position of the trapped droplets along the outlet channels of the microfluidic chip, we show lasing can be achieved for different positions of the droplet. When a trapped microdroplet is excited at a fixed position, lasing modes in the consecutive spectra of the droplet show a blue shift for all modes. The shift in modes is an indicator of the dissolution. Therefore, the next part focuses on dissolution of liquid microdroplets. Within a microfluidic chip, a trapped liquid microdroplet is exposed to planar extensional flow which increases the rate of the mass transfer out of the microdroplet. The static dissolution, that is diffusion, of droplets is modelled by Epstein and Plesset. However, the hydrodynamic trap induces flow around a trapped particle, therefore besides diffusion, the effect of convection should also be considered. The change in particle's radius as a function of time in the presence flow is numerically investigated by Zhang et al. To fit the experimental data we use the model provided by Zhang. The liquids used in the microdroplet dissolution experiments were n-octanol, n-decanol, undecanol and benzyl benzoate. Benzyl Benzoate and n-octanol showed good agreement with the Zhang model. In addition, experiments revealed that concentration of surfactant is an important parameter affecting dissolution rate which requires further investigation.