Typical in vitro barrier and co-culture models rely upon thick semi-permeable polymeric membranes that physically separate two compartments. Polymeric track-etched membranes, while permeable to small molecules, are far from physiological with respect to physical interactions with co-cultured cells and are not compatible with high-resolution imaging due to light scattering and autofluorescence. Here we report on an optically transparent ultrathin membrane with porosity exceeding 20%. We optimize deposition and annealing conditions to create a tensile and robust porous silicon dioxide membrane that is comparable in thickness to the vascular basement membrane (100–300 nm). We demonstrate that human umbilical vein endothelial cells (HUVECs) spread and proliferate on these membranes similarly to control substrates. Additionally, HUVECs are able to transfer cytoplasmic cargo to adipose-derived stem cells when they are co-cultured on opposite sides of the membrane, demonstrating its thickness supports physiologically relevant cellular interactions. Lastly, we confirm that these porous glass membranes are compatible with lift-off processes yielding membrane sheets with an active area of many square centimeters. We believe that these membranes will enable new in vitro barrier and co-culture models while offering dramatically improved visualization compared to conventional alternatives.

No abstract

No abstract

Ultrathin silicon-based nanomembranes hold significant promise for advancements in applications ranging from separations to tissue engineering. Widespread application of these membranes has been hindered by their small active area, which typically ranges from square micrometers to square millimeters. These membranes are typically supported on silicon chips as small windows as a result of a time-consuming through-wafer etch process. This approach results in a relatively low active area and can be challenging to integrate into devices because of the rigid silicon support. In this paper, a lift-off approach is demonstrated wherein the membrane is supported by a polymeric scaffold and separated from the wafer to enable fabrication of membrane sheets (>75 cm 2 ) with >80% active area. The wafer-scale lift-off process is demonstrated with 50 nm thick microporous and nanoporous silicon nitride (SiN) membranes. Release of large-scale SiN membranes is accomplished with both wet and dry lift-off techniques. The dry approach uses XeF 2 gas to etch a sacrificial silicon film, while the wet etch uses buffered oxide etchant to remove a silicon dioxide sacrificial layer. Finally, it is demonstrated that lift-off membranes have excellent optical properties and can be used to support cell culture on a conventional scale.

No abstract