Novel PDMS cylindrical channels that generate coaxial flow, and application to fabrication of microfibers and particles

In this paper, we introduce a novel cylindrical channel that generates coaxial flow without using glass microcapillary or complicated silicon processing, and we demonstrate the fabrication of microparticles and microfibers using this channel. The simple fabrication process for cylindrical channels employs the deflection of free-standing thin PDMS membranes. Using this channel, alginate microparticles and microfibers were fabricated without clogging the downstream channel, and the dimensions of these particles and fibers could be successfully controlled by regulating the flow rate through the channels. We also developed a method to integrate the coaxial flow channel into rectangular microfluidic channel devices, which have a broad array of established applications. As proof of concept of this technology, we fabricated a microfluidic chip that incorporated 12 rectangular micromixers to generate a stepwise gradient across discrete output streams. These output streams simultaneously fed into 5 coaxial flow channels, each of which produced a microfiber of a different chemical composition. The fibers or particles generated by the proposed method may be used in biomedical and tissue engineering, as well as in drug delivery. We expect that our method will facilitate the construction of microfluidic factories within single PDMS devices.