[0023] Several physical factors can modulate the beads' diameter, such as the diameter of the needle used to extrude the sol silica / alginate, the height at which the sol silica / alginate is dropped into the long chain polyamine solution, the speed at which the sol silica / alginate is dropped into the polycationic organic polymer solution, or the time of incubation of the beads in the coacervation solution.