Curing-state-dependent rheology governs electrospinning of silicone elastomers for hydrophobic surface coatings

Fibrosis around cochlear implant electrode arrays increases impedance and disrupts predictable stimulus propagation. Electrospun hydrophobic silicone coatings represent a promising strategy to mitigate fibrosis. However, electrospinning silicone elastomers remains challenging because their low glass transition temperature causes deposited fibers to collapse before curing is complete. Previous approaches have focused on developing in situ curing systems, such as heated collectors. Although fiber-like structures have been generated, nonwovens with interconnected pores have not yet been achieved. A pre-curing-based electrospinning strategy was developed that enables the fabrication of pure silicone elastomer nonwovens without the need for polymer blends, sacrificial carrier polymers, or coaxial spinnerets. Sylgard 184 dilutions in acetone and tetrahydrofuran were electrospun at different pre-curing times prior to gelation and characterized rheologically to investigate the influence of curing-induced rheological evolution on electrospinnability. Initially, the dilutions exhibited near-Newtonian flow behavior. Shortly before loss of flowability, the maximum first normal stress difference increased to 3228 Pa for acetone- and 6722 Pa for tetrahydrofuran-based systems, accompanied by increased storage modulus and more pronounced shear-thinning behavior. This rheological transition coincided with the transition from electrospraying to electrospinning. By controlling the curing time, nonwoven structures with well-defined fiber geometry and interconnected pores were successfully fabricated from Sylgard/tetrahydrofuran systems. Fiber diameters ranging from 21 µm to 136 µm were achieved by adjusting the diluent and curing time. These findings demonstrate that precise control of rheological evolution during curing enables the fabrication of structurally defined electrospun silicone elastomer nonwovens, providing a foundation for anti-fibrotic coatings on cochlear implants.