Direct casting of polymer membranes into microfluidic devices

Fully functional lab-on-a-chip devices for biological analyses require the capability for cell culture, separation, and purification, as well as analyses to be integrated on a single platform. To date, a great deal of research has been focused on analytical methods for the miniaturization of column-based separations. We have created a platform that provides the capability of including membrane separations as an intermediate stage in such devices. Our techniques adapt conventional silicon processing methods to the casting of membranes directly onto the silicon substrate through a wet inversion process. This process allows precise control of membrane thickness and pore size distribution based on the processing conditions. Using this methodology, we were able to fabricate devices that were found to be very robust with molecular weight cutoffs of approximately 350 Da as measured by solute flux in a dialysis mode of operation. These devices were also found to be suitable for cell culture, as evidenced by the high viability of fibroblasts grown within our device. On the basis of these results, a wide range of separations and coculture applications are possible.