Porous polymer monoliths: Simple and efficient mixers prepared by direct polymerization in the channels of microfluidic chips

Porous monolithic polymers have been prepared by photoinitiated polymerizat ion of mixtures consisting of 2-hydroxyethyl methacrylate, ethylene dimetha crylate, UV-sentitive free radical initiator and porogenic solvent within c hannels of specifically designed microfluidic chips and used as micromixers . Substituting azobisisobutyronitrile with 2,2-dimethoxy-2-phenylacetopheno ne considerably accelerated the kinetics of the polymerization. Mixtures of cyclohexanol and 1-dodecanol and of hexane and methanol were used, respect ively, to control the porous properties and therefore the mixing efficiency of the device. The performance of the monolithic mixers has been tested by pumping aqueous solutions of two fluorescent dyes at various flow rates an d monitoring the point at which the boundary of both streams completely dis appears. Best results were achieved with a monolithic mixer containing very large irregular pores.