Jiří Dohnal – PhD thesis summary

InkJet fabrication, characterization and application of calcium alginate microcapsules

The aim of this work is the preparation of structured microparticles from sodium alginate by an InkJet printhead with a piezoelectric actuator, which is able to generate droplets of solutions with a narrow size distribution. This technique is able to produce structured gel microparticles with size from 30 to 80µm. The goal of this work was the preparation of structured microparticles which can be used for controlled release of active substances or catalysis.

The first part of this work describes the principle of encapsulation and different methods for closing of active substances into particles. The next section of this work describes the properties of sodium alginate as a raw material used for the preparation of microparticles and the principle of InkJet technique. Advantages and disadvantages of this method and preparation of structured particles are mentioned at the end of this part.

The second part of this work deals with parametric studies of used InkJet printhead especially with respect to influences of parameters such as applied voltage, pressure in the system and liquid composition on the droplet size. Three types of liquids were used. The first of them was water, the second was a mixture glycerol and water with viscosity from 5 to 25 mPas and the third was a solution of sodium alginate with 0.5 and 1 wt.% concentration of polymer in water. The last type of printed fluid was a dispersion of TiO 2 microparticles (concentration from 2 to 8 volume percent) in 1wt.% of alginate solution.

The third part of this work describes different types of possible applications of structured microparticles. The first of them is encapsulation of catalyst (TiO 2 ) and usage of these microparticles for photodecompsition of pollutants in water. This work deals with preparation and modification of alginate particles for the highest photocatalytic efficiency. The second described application is the encapsulation of liposomes and magnetic nanoparticles. Liposomes in this particle have the role of thermoresponsive reservoirs for active substances.Magnetic particles heat the entire structure in the presence of alternating magnetic field. These particles are usable for controlled release of active substances directly in the target areas.