Engineering PDMS membranes with tunable biomimetic curvatures: from partial curing to vacuum-induced shaping

• Curved elastic membranes with vacuum-shaped from partially cured PDMS. • Fabrication parameters are critical for PDMS membrane lifting and curvature formation. • Membrane thickness and deflection tuned by vacuum power, frame size, and initial thickness. • Porous membranes exhibit pore enlargement after curvature formation. • The approach enables biomimetic 3D membranes for microphysiological systems. The development of biomimetic microenvironments requires microfabrication strategies capable of producing tunable three-dimensional structures. Conventional PDMS membranes used in microdevices generally lack curvatures, and commercially available porous membranes are similarly flat and mechanically limited in elasticity, restricting their capacity to replicate biological architectures and dynamic behaviors in biomedical applications. Here, we present a fabrication approach for PDMS membranes that enables controlled curvatures by integrating the partially cured state of PDMS with vacuum-induced shaping. By systematically optimizing fabrication parameters, including cuing timing for membrane detachment, frame sizes, and vacuum conditions, well-defined curvatures were achieved in PDMS membranes, accommodating diverse geometrical designs that better replicate the structural complexity of biological microenvironments. This method is also amenable to producing porous membranes with curvature; for membranes fabricated using SU-8 micropillars, optimization of the spin-coating duration and micropillar pitch was critical for porous membrane detachment. The resulting elastic PDMS membranes are suitable for integration into microdevices, and their combination of elasticity and biomimetic curvatures provides new opportunities for investigating tissue and cellular dynamics in biomedical research. Overall, this fabrication strategy offers a reliable and versatile platform for fabricating three-dimensional PDMS membrane structures to advance microphysiological systems