Robust and Gradient Thickness Porous Membranes for In Vitro Modeling of Physiological Barriers

Porous membranes are fundamental elements for tissue-chip barrier and co-culture models. However, the exaggerated thickness of commonly available membranes may represent a stumbling block impeding a more accurate in vitro modeling. Existing techniques to fabricate membranes such as solvent cast, spin-coating, sputtering, and plasma-enhanced chemical vapor deposition (PE-CVD) result in uniform thickness films. Here, a robust method to generate ultrathin porous parylene C (UPP) membranes is developed not just with precise thicknesses down to 300 nm, but with variable gradients in thicknesses, while at the same time having porosities up to 25%. Surface etching and increased roughness which lead to improved cell attachment is also shown. Next, the mechanical properties of UPP membranes with varying porosity and thickness is examined and the data is fitted to previously published models, which can help determine the practical upper limits of porosity and lower limits of thickness. Lastly, a straightforward approach allowing the successful integration of the UPP membranes into a prototyped 3D-printed scaffold is validated, demonstrating mechanical robustness and allowing cell adhesion under varying flow conditions. Collectively, the results support the integration and the use of UPP membranes to examine cell-cell interaction in vitro.