Generation of micro-sized PDMS particles by a flow focusing technique for biomicrofluidics applications

Polydimethylsiloxane (PDMS), due to its remarkable properties, is one of the most widely used polymers in many industrial and medical applications. In this work, a technique based on a flow focusing technique is used to produce PDMS spherical particles with sizes of a few microns. PDMS precursor is injected through a hypodermic needle to form a film/reservoir over the needle's outer surface. This film flows towards the needle tip until a liquid ligament is steadily ejected thanks to the action of a coflowing viscous liquid stream. The outcome is a capillary jet which breaks up into PDMS precursor droplets due to the growth of capillary waves producing a micrometer emulsion. The PDMS liquid droplets in the solution are thermally cured into solid microparticles. The size distribution of the particles is analyzed before and after curing, showing an acceptable degree of monodispersity. The PDMS liquid droplets suffer shrinkage while curing. These microparticles can be used in very varied technological fields, such as biomedicine, biotechnology, pharmacy, and industrial engineering.The authors acknowledge the financial support provided by Fundação para a Ciência e a Tecnologia (FCT), COMPETE and FEDER through the Projects PTDC/SAU-ENB/116929/2010, EXPL/EMS-SIS/2215/2013, PTDC/QEQ-FTT/4287/2014 and fellowship SFRH/BD/89077/2012. Partial support from the spanish Ministry of Science and Education (Grant No. DPI2013-46485), Junta de Extremadura (Grant No. GR10047), and “la Caixa” Foundation (predoctoral grant) is gratefully acknowledged too. Finally, we thank Jos e M. Montanero for his helpful suggestions and discussion on the results.