Summary
Electrospinning is shaped by many process and environmental variables, and ambient humidity is one of the most frequently overlooked. This study systematically investigates how relative humidity (RH) during electrospinning affects the morphology and mechanical properties of nanofibres, keeping solution and process parameters constant so the humidity effect can be isolated. Working with poly(vinyl alcohol) (PVA), poly(ethylene oxide) (PEO) and their blends with hyaluronic acid and chitosan, the authors show that fibre shape and diameter can be tuned by precisely regulating RH: fibre diameters fell substantially as humidity rose, while very high RH led to bead formation and, for the blends, to loss of continuous spinning. Because fibre diameter is linked to rigidity, controlling RH becomes a way to tune mechanical behaviour, and the solution's rheological phase-shift angle is used to predict when a homogeneous nanofibre structure will be lost.