O2 permeability of additively manufactured silicone membranes

Abstract Silicone is already widely used in biomedical applications thanks to its outstanding properties. Now additive manufacturing (AM) of silicone can achieve submillimeter details and is offered by SpectroPlast AG as a service. AM of silicone is particularly interesting for designs with complex internal structures such as bioreactors or oxygenators where oxygen permeability is important. Therefore, the oxygen permeability of additively manufactured silicone membranes made from TrueSil (SpectroPlast AG) is studied. Measurements are performed with two membrane thicknesses (0.5 and 0.8 mm) and four different Shore hardnesses (20A, 35A, 50A, and 60A) at 15, 20, and 25°C. The oxygen increase due to diffusion through the membrane is recorded In a cup sealed by the membrane. The oxygen permeability decreases with increasing Shore hardness. TrueSil 20A is comparable to ELASTOSIL® Film (Wacker Chemie AG) in terms of oxygen permeability. However, there is a percentage difference of approximately 27% between the measured permeability of ELASTOSIL® and the data from the supplier. Membrane thickness does not affect permeability, but the Shore hardness affects the thickness. Membranes with Shore hardness 20A or 35A are manufactured over 0.1 mm thicker than designed, while for Shore hardness 50A and 60A the deviation from the design is less than 0.04 mm.