The mechanical properties of the microcapsules were assessed by monitoring the inflation of the capsules in hypotonic solutions of dextran. Experimentally, the droplet phase is dissolved with 15% dextran (Mw=500,000), and the external phase is replaced by dextran solutions with different concentrations (1%~15%, w/v). Due to the presence of concentration gradient of dextran, an osmotic pressure is introduced to the capsules and drive their slow inflation (Fig. ). When the concentration of dextran in the external phase is reduced to 1 wt%, a high osmotic pressure of about 60 mOsm/Kg is generated, and the capsules remain intact without rupture. The expansion ratio of surface area, η, defined by of nutrients, and metabolic waste across the membrane. Resistance of microcapsules against shear force is further characterized by suspending capsules in dextran solution and measured using a rotational rheometer.