Moreover, the applicability of microfluidic blood oxygenators at a clinical scale is closely tied to the available manufacturing technologies and materials. Current microfabrication techniques are labourintensive, limiting the production rates, and based on fabrication methods that limit channel depth to a single level. In addition, all the microfluidic devices proposed up to now are produced by lithography methods, which impair the creation of circular channels, and are made of PDMS which makes them not compatible with the actual massproduction techniques. A promising solution may be high-resolution 3D printing or precision computer numerical control (CNC) machining since they are capable of fabrication at the microscale level with great degree of freedom in size and 3D designs. other authors suggested some unconventional techniques, for instance, using lubricant-infused mould, combining PDMS membrane with SU-8 and quartz or developing materials or hybrid microfluidic structures with better performances than PDMS for biomedical applications 228 .