A Parametric Analysis of Capillary Height in Single-Layer, Small-Scale Microfluidic Artificial Lungs

Abstract

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.

Toward 3D printed microfluidic artificial lungs for respiratory support

“…For this reason, decreasing artificial capillary height will be a priority in the future for pushing the technology to larger blood flows and thus toward the clinic. As we have previously shown, 10,47 reducing artificial capillary height can dramatically decrease Fig. 5 Predicted rated flow (mL min −1 ) for μAL performance vs. capillary height.…”

“…For this reason, decreasing artificial capillary height will be a priority in the future for pushing the technology to larger blood flows and thus toward the clinic. As we have previously shown, 10,47 reducing artificial capillary height can dramatically decrease the device's blood contacting surface area and blood priming volume, reducing overall device size and potentially increasing blood compatibly (due to less foreign surface exposed to blood). Smaller artificial capillaries come with other challenges, however, mainly due to pressure drop increases proportional to the inverse of capillary height cubed ( H C −3 ).…”

Empirical and Computational Evaluation of Hemolysis in a Microfluidic Extracorporeal Membrane Oxygenator Prototype

“…Microfluidic-based devices with high-permeability membranes could revolutionize the extracorporeal membrane oxygenation (ECMO) process by reducing the blood volume, blood contacting surface area, and overall device size [ 10 , 11 , 12 , 13 , 14 ]. Reduced blood volume is helpful to all patients and critical for smaller patients, such as neonates, as the priming volume of conventional medical devices sometimes exceeds the total blood volume of a neonate [ 15 , 16 , 17 ].…”