FIGURE: Schematic illustration of the electrospinning process
Several parameters can be tuned in electrospinning to control fiber formation and morphology. Process parameters (voltage, solution flow rate, distance from needle to collector) and environmental conditions (humidity, temperature) critically affect the diameter and uniformity of fibers. For example, higher voltages generally produce thinner fibers up to a point, while humidity can influence solvent evaporation and fiber continuity. Solution properties are equally important – polymer concentration, viscosity, conductivity, and solvent volatility determine whether a stable jet can form without breaking into droplets (a phenomenon known as beading). By optimizing these factors, one can customize fibers for specific applications, from smooth continuous nanofibers to porous or core–shell structures. The versatility of electrospinning is such that it can accommodate a wide range of polymers (natural and synthetic) and even incorporate bioactive molecules or nanoparticles into fibers. This level of control, coupled with the simplicity of the apparatus, makes electrospinning a powerful technique for engineering materials that closely mimic extracellular matrices or have other desirable nanoscale features (Ji et al., 2024).
Below, the principal parameters are organized into four groups—solution/material, process/equipment, environment, and deposition/throughput—each with a brief rationale for why it matters and how it influences fiber formation. The intent is to provide a generally applicable framework for most electrospinning use cases, independent of end application.
1) Solution & material parameters
Polymer selection: chemistry, molecular weight, & chain architecture
Polymer identity sets the baseline viscoelasticity, entanglement density, and solidification pathway (glassy vs semicrystalline), which together govern jet stability and the ability to form bead-free continuous fibers. Sufficient molecular weight and chain entanglements are required to avoid Rayleigh breakup; too few entanglements yield beads or droplets, while very high molecular weight can impede pumping and cause intermittent jets (Ji et al., 2024).
Polymer concentration & viscosity
Concentration tunes viscosity and entanglement number. At low concentration, insufficient elasticity produces beads-on-a-string; at moderate concentration, uniform fibers emerge; at very high concentration, solutions may not flow well and can clog nozzles. The usable window is polymer- and solvent-specific and should be mapped empirically for each formulation (Ji et al., 2024).
Solution conductivity & surface tension
Higher conductivity increases the charge carried by the jet, enhancing elongational forces and often reducing fiber diameter; however, excessive conductivity can destabilize the jet (multiple whipping modes). Surface tension resists jet formation; modest reductions (via solvent choice or surfactants) can aid spinnability but must be balanced to maintain a stable Taylor cone (Ji et al., 2024).
Solvent selection (volatility, boiling point, dielectric constant, toxicity)
The solvent system controls evaporation rate and therefore when the jet “freezes” into a solid fiber. Highly volatile solvents promote rapid solidification (favoring circular cross-sections), while slower-evaporating systems can yield ribboned or porous fibers if drying is delayed. Dielectric properties also influence charge density and jet stretching. There is increasing emphasis on “benign/green” solvent systems (e.g., ethanol-, water-, or citrate-based) to reduce environmental and occupational hazards, with current definitions and decision frameworks summarized by Avossa et al. (2022).
Solution temperature
Elevating solution temperature lowers viscosity and surface tension, typically thinning fibers; excessive heating can increase solvent vapor pressure and introduce jet instabilities. Quantitatively, increasing working temperature can reduce fiber diameters by tens of percent depending on the polymer/solvent system (Yang et al., 2017).
2) Process & equipment parameters
Applied voltage and electric field geometry
Voltage must exceed the threshold for Taylor cone formation; beyond that, higher field strength generally increases elongational forces and can reduce diameter up to an optimum, after which whipping instabilities and bead formation may increase. Electrode geometry (ancillary plates, field-shaping shields) can stabilize multi-jet arrays and improve uniformity across a wider deposition area (Beaudoin et al., 2022).
Flow rate
Flow must replenish the Taylor cone without overfeeding. Too low a rate causes intermittent jets; too high a rate produces wet fibers, beads, or fused mats due to insufficient solvent removal before impact. In closed-loop control schemes, small pump-rate adjustments (e.g., ±2%) are used as actuators to maintain setpoints for thickness and fiber diameter (Ji et al., 2024).
Tip-to-collector distance (TCD)
TCD sets the residence time for stretching and solvent evaporation. Short TCDs can yield wet deposition, ribboning, or fiber fusion; longer TCDs allow more thinning but can increase whipping, overspray, and nonuniformity. TCD is co-optimized with volatility, humidity, and voltage to land at the same “dry state” upon impact (Ji et al., 2024).
Spinneret type and needle geometry
Single-needle setups are versatile and controllable; multi-needle arrays raise throughput but can suffer from jet–jet interactions unless fields are flattened or shielded (Beaudoin et al., 2022). Coaxial or triaxial spinnerets enable core–shell or multi-compartment fibers for encapsulation and functionally graded profiles. Inner diameter and wall thickness of the needle influence shear history and clogging propensity.
Collector type and motion
Static plates favor random mats; rotating drums/mandrels and patterned collectors can impart alignment or texture. Continuous transport systems (e.g., segmented “wafer” collectors) support high-volume production while minimizing mechanical compression of still-drying fibers, improving thickness uniformity across large areas.
3) Environmental parameters
Relative humidity (RH)
Ambient RH influences solvent evaporation kinetics and fiber surface morphology. A 10–20% RH increase can drive transitions from smooth cylinders to porous or wrinkled/ribbon morphologies in certain systems due to phase separation during drying (Putti et al., 2015; Zhang et al., 2020). Tight RH control is therefore essential for reproducible diameter and surface texture.
Ambient temperature and airflow/solvent vapor
Higher temperature accelerates evaporation and lowers solution viscosity, typically thinning fibers but potentially increasing defects if drying is too rapid or nonuniform (Yang et al., 2017). Local airflow and solvent vapor around the needle tip can stabilize the Taylor cone and reduce beading—especially for volatile solvent systems—by moderating evaporation right at the jet origin.
Electrostatic environment and charge management
As mats thicken, residual charge on deposited fibers can repel incoming jets, limiting build height and promoting nonuniform laydown. Strategies include adjusting collector potential or active ionization to neutralize charge and maintain stable deposition during long builds.
Summary
Electrospinning outcomes result from a tightly coupled parameter set: fluid properties (entanglement, viscosity, conductivity, surface tension; solvent choice), operating conditions (field strength, flow, TCD, nozzle geometry), ambient environment (temperature, humidity, vapor, charge management), collector design and motion, and the selected spinning mode for scale-up. Establishing and maintaining an appropriate window across these factors enables consistent control of diameter, morphology, alignment, porosity, and layer architecture—independent of end-use domain
