Monolithic fabrication of three-dimensional microfluidic networks for constructing cell culture array with an integrated combinatorial mixer

We present a novel method to monolithically fabricate three-dimensional (3-D) microfluidic networks and based on this fabrication technology, we have constructed the first cell culture device with an integrated combinatorial mixer. The device is designed for screening the combinatorial effects of multiple compound exposure on cultured cells, and a 1 cm 1 cm proof-of-concept chip having a three-input combinatorial mixer and eight individually isolated micro culture-chambers has been fabricated. The 3-D microfluidic networks are fabricated utilizing the surface micromachining of parylene C (poly(chloro-p-xylylene)), and the monolithic method enables the device to achieve precise alignment in between microchannels and favorably obviates multilayer bonding processes. By incorporating several microfluidic overpass structures to allow one microfluidic channel to cross over other microfluidic channels, the combinatorial mixer is able to simultaneously generate all the combinations of the input fluidic streams for output to the microchambers. Cell culturing inside parylene C micro culture-chambers has been successfully performed, and the ability to simultaneously treat arrays of cells with different combinations of compounds has been demonstrated with experiments using three different cell stains. Our scaleable process can enable the fabrication of devices with a high-input combinatorial mixer with applications not only for high-throughput cell-based assays but also for conducting researches in combinatorial chemistry or the pharmaceutical industry. At the same time, the fabrication technique will have general applicability for building complex 3-D microfluidic devices, which can broaden the applications for current lab-on-a-chip systems.