Extensional rheology and electric field control: strategies for electrospinning scale-up

Abstract

Polymeric nanofibers are increasingly used in filtration, sensing, and biomedical applications. Electrospinning offers a versatile route to produce such fibers with controlled morphology, but its adoption beyond the laboratory remains limited by intrinsically low productivity. Simply increasing the flow rate collapses fiber morphology, showing that scale-up requires new strategies. This thesis addresses two critical challenges: tailoring the rheological properties of polymer solutions to optimize fiber formation, and mitigating electric field non-uniformities in multi-needle systems that destabilize jets and compromise product quality. The first research path focuses on rheology. A custom Capillary Breakup Extensional Rheometer (CaBER) was designed for low-viscosity viscoelastic solutions relevant to electrospinning. Controlled-humidity experiments and an evaporation–diffusion model revealed that solvent evaporation strongly biases filament thinning, conflating intrinsic relaxation time with evaporation-driven strain hardening. Systematic studies on molecular weight distribution showed that long-chain content governs extensional elasticity and fiber morphology. Crucially, elastic doping, with a trace fraction of high-molecular-weight polymer, enabled fiber formation from an otherwise unspinnable low-molecular-weight matrix, leading to a fivefold increase in polymer throughput while preserving fiber quality. The second research path addresses scale-up via multi-needle electrospinning. A linear twentyneedle array was investigated, and parallel plates as auxiliary electrodes were introduced to homogenize the electric field. Finite element simulations and experiments demonstrated that this approach stabilizes jet trajectories, uniformizes fiber deposition, and enables precise control of membrane thickness. This configuration achieved a twentyfold increase in production rate while maintaining fiber quality comparable to single-needle electrospinning. Together, these findings demonstrate that combining rheological control of solution formulations with electric field optimization provides a practical and scalable framework for nanofiber production. This work advances electrospinning from laboratory-scale studies toward industrially relevant throughput.

Date	20 Nov 2025
Original language	American English
Awarding Institution	École de technologie supérieure
Supervisor	Nicole R. Demarquette (Supervisor) & Ricardo J. Zednik (Co-supervisor)