Inkjet fabrication and characterization of calcium alginate microcapsules

The present work describes a method for producing calcium alginate hydrogel microcapsules in the size range of 50-70 mu m by means of a piezoelectric drop-on-demand inkjet device. Particles were prepared by emitting droplets of 0.5% and 1% (w/w) sodium alginate solutions into a magnetically stirred pool of CaCl2 solution of variable viscosity ranging from 1 to 100 mPas. The effect of viscosity on the morphology of the resulting microcapsules was systematically investigated - lower viscosity of the receiving solution has lead to the formation of elongated particles, medium viscosities lead to spherical capsules, and for higher viscosities flattened particles were obtained. The applied voltage used for driving the piezoelectric inkjet print-head was found to be the most significant parameter for influencing the droplet size. The duration of the voltage pulse or the droplet viscosity had only minor effects. The release rates of two model substances (methylene blue dye and vitamin 812) from alginate beads were measured and their effective diffusion coefficients determined as function of alginate concentration. (C) 2010 Elsevier B.V. All rights reserved.