Fabrication of microfluidic devices for artificial respiration

Abstract

We are developing elastomeric polydimethylsiloxane (PDMS) microfluidic devices incorporated with photoactive thin films to create an implantable artificial respiration platform. Whereas state-of-the-art respiration support machines deliver oxygen gas directly to the blood via external macroscale devices, our technique utilizes a biomimetic photocatalytic process to generate energy from light and thus produce dissolved oxygen from water which is already present in the blood. Blood oxygenation will be achieved by the interaction between the photoactivated metal oxide film and blood in the setting of a molded microfluidic conduit, providing a stable and implantable oxygenation platform. As a basic, scalable building block, we developed a noble "network" design which was structurally similar to the native pulmonary capillary network. The interconnected channel geometry was designed in such a way to minimize shear stress and reduce hemolysis and thrombosis inside the microchannel. It allowed alternative flow pathways in the event of single channel occlusion while minimizing the establishment of detrimental pressure gradients. The hemocompatibility analysis demonstrated that the network construct showed acceptable levels of hemolysis rate (< 8%) and thrombus formation.

(cont.) Critical to the success of this project is the understanding of the manufacture parameters for microfluidic devices molded from elastomeric materials like PDMS. In the initial development of our work, we performed the following three tasks to generate manufacture protocols for elastomeric microfluidic devices that will be ultimately used for biological applications: 1) Curing schedules of the heat-cure PDMS elastomers under various fabrication parameters were characterized. 2) The interlayer bonding chemistry of the double layer PDMS device was analyzed followed by subsequent mechanical analysis. 3) The efficacy of various surface treatment techniques on hydrophobic PDMS surfaces was investigated using fluorescently tagged bacteria (E. Coli) flowed through microchannels as reporter particles to measure non-specific adhesion, which will provide useful information in minimizing channel fouling for biological applications.