PDMS-silica composite gas separation membranes by direct ink writing

Polydimethylsiloxane (PDMS)-based membranes containing amine-functionalized and unfunctionalized silica particles were fabricated via direct ink writing for CO₂/N₂ gas separation. The printability of the inks was evaluated by rheological measurements, while spectroscopy, microscopy, thermal measurements, and mechanical testing were employed to characterize the printed membranes. The surface morphology of the membranes revealed the absence of voids, demonstrating their suitability for gas separation. The printed membranes also exhibited desirable thermal and mechanical properties (i.e., thermal degradation temperature of 518 °C and tensile strength as high as 1.178 MPa with 529% elongation). The PDMS-based membranes generally displayed high permeability for CO₂ but slightly low selectivity for the CO₂/N₂ gas pair. The best-combined permeability-selectivity performance of 8794 barrer and selectivity of 11.64 was demonstrated by the printed PDMS membrane containing no SiO₂ fillers. The inclusion of unfunctionalized SiO₂ particles generally increased the membrane's gas permeability but compromised the selectivity. In contrast, membranes with amine-functionalized silica showed improved selectivity compared to membranes containing unfunctionalized silica. Overall, the performance and characteristics offered by the PDMS/silica composite membranes demonstrated the potential of 3D printing as an economical and sustainable fabrication approach to developing materials for carbon capture applications.