In the following years, many research groups developed and tested new micro-oxygenators. Particularly of note is the work of who created a microfluidic lung assist device with a 9 μm-thick silicon membrane and a 100 μm-tall, blood channels network with physiological blood flow. They applied the natural branching and scaling as described by Murray's law 211 , coupled with iterative computational fluid dynamic analysis to create a vascular network with uniform flow at bifurcations, biomimetic vessel length, and shear stress in the arterial range. However, the limitation to a single channel height throughout the entire network imposed by photolithography limited the gas exchange efficiency of the microchannels.