Water droplet encapsulation by a quantitative and removable oil shell

In this paper, we demonstrate the method to generate an encapsulated droplet with precisely controlled water to oil volume ratio by merging individually created water and oil droplets through EWOD (electrowetting-on-dielectric) and DEP (dielectrophoresis) actuations, respectively. In addition, the 10cSt oil shell can be removed by mixing it with a volatile solvent. A bare droplet is obtained after the mixture is evaporated.