Synthesis of bio-functionalized copolymer particles in 3D microfluidic devices

This paper proposes a design concept and fabrication method of a planar three-dimensional (3D) microfluidic flow-focusing device (MFFD) that can produce monodisperse copolymer (EGDMA/AA) microspheres carrying surface carboxyl in a closed/open microfluidic system. The devices were made up by PDMS or SU-8 resist structures to form coaxial embedded orifices for a closed/open microfluidic system, respectively. The copolymer microspheres produced in an open channel configuration can avoid the problem of clogging the microchannels during in-situ UV polymerization. By confining the comonomer liquid thread to the central axis of the microchannel, we avoid the wetting problem and successfully produced copolymer microspheres with diameters ranging from 95%m to 140%m and coefficient of variance (CV) below 4%. Besides, increasing the concentration of acrylic acid (AA) would decrease the particle size, but increase the distribution of carboxyl group on the particle surfaces. Bioconjugation of the carboxylated copolymer particles with the anti-rabbit IgG-Cy3 conjugates was successfully produced. The unique fabrication overcomes problems encountered for current 2D MFFD devices, and provides flexibility for lab-on-chip microsystems.