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Electrospinning researchers often encounter a frustrating situation: the polymer formulation, voltage, flow rate, and working distance remain unchanged, yet the fibers produced today look different from those produced yesterday.
The reason may not be the machine or the formulation. It may be the environment.
Temperature and relative humidity (RH) influence solvent evaporation, solution viscosity, charge dissipation, jet solidification, fiber diameter, surface morphology, and process repeatability. For this reason, they should be treated as process parameters, not simply as room conditions.
Understanding their effects can help researchers reduce trial-and-error and achieve more reproducible electrospinning results.
During electrospinning, a charged polymer jet travels from the spinneret toward the collector while being stretched and losing solvent.
For stable fibers to form, several processes must occur at the right rate:
the solution must flow consistently;
the jet must remain sufficiently stable;
the solvent must evaporate;
the polymer must solidify before reaching the collector;
electrical charges must dissipate appropriately.
Temperature and humidity can influence several of these processes at the same time.
This is why two experiments with identical voltage and flow rate can still produce different fiber morphologies when the surrounding environment changes.
Temperature mainly affects electrospinning through two mechanisms:
For many polymer solutions, increasing temperature reduces viscosity.
A lower-viscosity solution may stretch more easily under the electric field, which can sometimes lead to finer fibers. However, if viscosity becomes too low, the polymer chains may no longer provide sufficient entanglement for stable fiber formation.
The result may be:
beads;
irregular fibers;
unstable jets;
electrospraying instead of continuous electrospinning.
Conversely, lower temperatures may increase viscosity, making the solution more difficult to deliver and stretch.
Higher temperatures generally accelerate solvent evaporation.
This can be helpful when fibers are arriving at the collector too wet. However, excessive evaporation can create new problems, especially near the needle tip.
Possible symptoms include:
needle clogging;
dried polymer around the spinneret;
unstable Taylor cone;
inconsistent fiber diameter.
Therefore, increasing temperature is not automatically an improvement. The correct temperature depends on the polymer, solvent system, flow rate, and target fiber structure.
Relative humidity is particularly important because water vapor can influence both the electrical behavior of the jet and the way the solvent evaporates.
Depending on the polymer and solvent system, changes in humidity may affect:
fiber diameter;
bead formation;
surface roughness;
internal or surface porosity;
fiber fusion;
mechanical properties;
membrane uniformity.
For some hydrophobic polymer systems, moisture condensation during solvent evaporation can contribute to pore formation on the fiber surface.
For hygroscopic or water-sensitive materials, higher humidity may instead interfere with jet stability, solidification, or material properties.
This is why statements such as “high humidity is always bad for electrospinning” are too simplistic.
The actual effect must be evaluated for the specific polymer–solvent system.
Environmental problems often appear as fiber defects rather than as obvious equipment alarms.
Possible causes:
insufficient solvent evaporation;
high flow rate;
short tip-to-collector distance;
unfavorable temperature or humidity conditions.
First check whether the fibers are fully solidified before reaching the collector.
Possible causes include rapid solvent evaporation, moisture interaction, and phase-separation effects.
Porosity is not necessarily a defect. In filtration, biomedical, or functional membrane applications, controlled surface porosity may actually be desirable.
The important point is whether the morphology is intentional and repeatable.
If material repeatedly dries at the spinneret, consider:
solvent volatility;
temperature;
airflow;
flow rate;
solution concentration.
Increasing voltage alone will normally not solve this problem.
This is one of the strongest signs that environmental conditions should be investigated.
Compare:
room temperature;
relative humidity;
solution age;
solvent batch;
spinning duration;
ventilation conditions.
If voltage, flow rate, and geometry are unchanged but morphology varies significantly, the environment may be an uncontrolled variable.
There is no universal answer.
A commonly made mistake is to look for one “ideal” humidity or temperature range that applies to every electrospinning process.
Such a range does not exist.
The appropriate environmental window depends on factors including:
polymer type;
polymer concentration;
solvent or solvent mixture;
solution conductivity;
solution viscosity;
hygroscopicity;
target fiber diameter;
desired surface morphology.
For example, a humidity level that creates useful porous fibers in one material system may produce unstable or fused fibers in another.
Published values should therefore be treated as starting points for experimental development, not universal specifications.
The better question is:
What temperature and humidity range gives this material system stable and reproducible results?
For research work, environmental data should be recorded together with the traditional electrospinning parameters.
A useful experiment record should include:
polymer and solvent formulation;
solution concentration;
solution preparation time;
solution age;
voltage;
flow rate;
needle diameter;
tip-to-collector distance;
collector type and speed;
temperature;
relative humidity;
spinning time.
Once a successful process window has been identified, repeat several experiments under similar environmental conditions.
If the results become more consistent, temperature or humidity was likely contributing to previous variation.
Changing only one major variable at a time also makes troubleshooting much easier.
Not every preliminary electrospinning experiment requires a fully controlled environment.
For early material screening, monitoring room temperature and humidity may be sufficient.
Environmental control becomes more valuable when:
experiments must be reproduced over weeks or months;
fiber diameter must remain within a narrow range;
morphology is highly sensitive to humidity;
porous fiber structures are being deliberately developed;
long-duration spinning is required;
different researchers must reproduce the same process;
results are being prepared for publication;
a laboratory process is moving toward pilot-scale production.
In these situations, simply displaying temperature and humidity is different from actively controlling them.
An enclosed electrospinning system with temperature monitoring, humidity management, controlled ventilation, and stable airflow can help reduce environmental variation.
For example, AME ENERGY's laboratory electrospinning platforms include configurations with integrated heating, humidity monitoring, dehumidification, and controlled airflow. The appropriate configuration should still be selected according to the actual polymer, solvent, and experimental objective.
No. Humidity can influence fiber diameter, but the direction and magnitude of the effect depend on the polymer and solvent system. It may also change porosity, surface morphology, or jet stability.
Yes, humidity can contribute to unstable fiber formation in some systems, but beads may also result from low viscosity, low polymer concentration, excessive flow rate, surface tension, or unsuitable voltage. Humidity should therefore be considered together with other process variables.
Not necessarily for initial screening. However, active environmental control becomes increasingly useful when repeatability, long-duration experiments, sensitive materials, or scale-up are important.
Temperature and humidity are not secondary conditions in electrospinning. They are part of the process.
Their effects are closely connected to solution viscosity, solvent evaporation, charge behavior, jet stability, and fiber solidification.
The most reliable approach is not to search for a universal “best humidity,” but to establish an environmental process window for the specific polymer–solvent system being studied.
Once that window is understood and controlled, electrospinning becomes easier to reproduce, troubleshoot, and eventually scale up.
How to Choose an Electrospinning Machine for Laboratory Research
Common Electrospinning Problems and How to Solve Them: A Practical Troubleshooting Guide
If your laboratory is experiencing inconsistent fiber morphology or needs better control of temperature, humidity, collection, or solution delivery, share your polymer, solvent system, target fiber structure, and current process conditions with AME ENERGY.
Our team can help evaluate a suitable electrospinning configuration based on your actual research requirements.
Szewczyk, P. K. et al. The Impact of Relative Humidity on Electrospun Polymer Fibers: From Structural Changes to Fiber Morphology. Advances in Colloid and Interface Science, 2020, 286, 102315.
Shaban, M. et al. Advancements in Electrospinning: A Comprehensive Review of Historical Development, Key Parameters, Applications, and Challenges. Discover Chemistry, 2026.
AME ENERGY. Laboratory Electrospinning Systems and Environmental Control Configurations.
