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Microfluidic artificial lungs (μALs) are being investigated for their ability to closely mimic the size scale and cellular environment of natural lungs. Researchers have developed μALs with small artificial capillary diameters (10–50 µm; to increase gas exchange efficiency) and with large capillary diameters (~100 µm; to simplify design and construction). However, no study has directly investigated the impact of capillary height on μAL properties. Here, we use Murray's law and the Hagen-Poiseuille equation to design single-layer, small-scale μALs with capillary heights between 10 and 100 µm. Each µAL contained two blood channel types: capillaries for gas exchange; and distribution channels for delivering blood to/from capillaries. Three designs with capillary heights of 30, 60, and 100 µm were chosen for further modeling, implementation and testing with blood. Flow simulations were used to validate and ensure equal pressures. Designs were fabricated using soft lithography. Gas exchange and pressure drop were tested using whole bovine blood. All three designs exhibited similar pressure drops and gas exchange; however, the μAL with 60 µm tall capillaries had a significantly higher wall shear rate (although physiologic), smaller priming volume and smaller total blood contacting surface area than the 30 and 100 µm designs. Future μAL designs may need to consider the impact of capillary height when optimizing performance. [ABSTRACT FROM AUTHOR]

Objective: Microfluidic artificial lungs (μALs) are being researched for future clinical use due to the potential for increased gas exchange efficiency, small blood contacting surface area, small priming volume, and biomimetic blood flow paths. However, a current roadblock to clinical use is the need to stack hundreds to thousands of these small-scale μALs in parallel to reach clinically relevant blood flows. The need for so many layers not only increases the complexity and projected cost to manufacture a μAL, but also could result in devices which are cumbersome, and, therefore, not suitable for portable artificial lung systems. Methods: Here, we describe the design analysis and optimization of a single-layer μAL that simultaneously calculates rated blood flow, blood contacting surface area, blood volume, pressure drop, and shear stress as a function of blood channel height using previously developed closed-form mathematical equations. A μAL designed using this procedure is then implemented and tested. Results: The resulting device exhibits a rated flow of 17 mL/min and reduces the number of layers required for clinically relevant μAL devices by a factor of up to 32X compared to previous work. Conclusion: This procedure could significantly reduce manufacturing complexity as well as eliminate a barrier to the clinical application of these promising devices. Significance: The described method results in the highest rated flow for any single-layer μAL to date. [ABSTRACT FROM AUTHOR]