Engineering Tunable and Anisotropic Mechanical Properties in Electrospun Membranes via Thermal Annealing

Polymeric porous membranes are widely used in applications, such as water filtration, tissue engineering, and drug delivery, where their mechanical properties are critical for structural integrity, durability, and optimal performance. However, achieving tunable and anisotropic mechanical behavior remains a key challenge, particularly in electrospun systems, where random fiber deposition often limits property control. In this study, near-field electrospinning (NFES) combined with thermal annealing was employed to fabricate PLGA membranes with enhanced and tunable mechanical properties. Tensile testing revealed that elevating annealing temperatures substantially increased Young’s modulus and yield stress, accompanied by a transition from ductile to brittle fracture. Load–unload cyclic strain testing further revealed initial structural rearrangements, followed by stabilization, indicating improved elastomeric recovery. Notably, XRD analysis confirmed that the stiffening effect of annealing occurred without detectable PLGA crystallization, suggesting that junction fusion and solvent evaporation were the primary mechanisms for strength enhancement. Anisotropic design and junction analysis highlighted the critical role of fiber junctions in reinforcing the membrane structure, while bending tests confirmed progressive improvements in stiffness and resistance to deformation. The successful fabrication of self-standing 3D spherical architectures demonstrates the versatility of this approach in enabling mechanically robust membrane platforms. Together, these findings provide insights into the interplay between thermal processing and fiber architecture, offering a pathway to engineer advanced membranes for next-generation applications in tissue engineering, filtration, and beyond.