Electrospinning: Understand Fibre Formation and Scale-Up Constraints

An electrospun layer may look good under a microscope. Turning it into a useful textile can still be hard. The fibres may vary across the width. Too much of the polymer may miss the carrier. A film that passes its first airflow test may peel away during later handling.

These are different problems, so they need different evidence. A sound project links how fibres form with what reaches the roll. It also checks usable output and how the final product performs.

This guide explains solution electrospinning from that viewpoint. The worked examples use fictional figures. They show how to compare results and work out capacity. They are not polymer recipes, machine settings or universal product limits.

Follow the material from liquid to a finished layer

Electrospinning uses an electric field to draw a fine jet from a liquid. In the solution process, this liquid contains polymer and solvent. The solvent must leave as the fibre forms and dries. The finished material may be deposited on a carrier that supports later processing.

Near the source, electrical forces deform the liquid surface. A cone-shaped region, commonly called a Taylor cone, can feed a jet. The material and the electric field affect the jet's path and stretching. So does the air around it.

The jet does not simply fall straight down and become a fibre of fixed size. Reneker and colleagues studied bending instability. A nearly straight jet can start to bend along a complex path. Electrical forces stretch and thin it as this happens. Their model also considers the liquid's elastic and viscous behaviour.

That distinction matters when watching a trial. A moving jet shows that material is flowing. It does not tell us the final diameter, dryness or collection yield. Measure those properties on the material that reaches the collector.

The carrier adds another stage. A useful layer must stay attached during winding and transport. It must also withstand any later coating or lamination step. The support can also contribute much of the finished material's mass and strength. Name the support and the electrospun layer separately in the test record. This keeps their results distinct.

Link each record to the next. Start with the solution batch and run conditions. Then record where material was collected, which specimen was tested and its result. Without that chain, a good micrograph may be impossible to link to the roll offered to a customer.

Define fibre size before discussing benefits

The term “electrospun” describes how material was made. It does not guarantee that every fibre has a diameter below one micrometre. Report actual measurements in nanometres, written nm, or micrometres, written µm. One µm equals 1,000 nm.

Smaller diameter can increase surface area per unit mass. The size of that increase depends on which fibres are compared. One multiplier will not fit every material.

Consider an ideal long, solid cylinder with diameter d, length L and density ρ. Ignore its ends. Its side area is πdL, and its mass is ρπd²L ÷ 4. Dividing the first expression by the second gives:

Ideal side area per unit mass = 4 ÷ (ρ × d).

Use consistent units. Suppose the assumed density is 1,200 kg/m³ and the diameter is 400 nm, or 0.0000004 m. The result is about 8,333 m²/kg, equivalent to 8.33 m²/g.

At the same density, a 4 µm cylinder gives about 833 m²/kg, or 0.833 m²/g. The smaller fibre therefore has tenfold more ideal side area per mass.

This is a geometric illustration. It does not measure accessible surface area in a real web. Fused contacts and coatings can change the result. Internal pores and the range of fibre sizes matter too. It also does not prove filtration efficiency, strength or skin comfort. Each of those claims requires its own test.

Treat process variables as a connected system

Specify the solution beyond its concentration

A concentration value needs a basis. A mass percentage describes polymer mass divided by total solution mass. A mass-per-volume expression uses a different denominator. Neither should be entered into the other's calculation without the required conversion data.

Polymer identity and grade matter too. Two batches can share the same polymer name and concentration yet differ in viscosity. Molecular weight, solvent composition and solution condition can affect how the liquid stretches.

Nezarati, Eifert and Cosgriff-Hernandez studied humidity and viscosity effects in three polymer systems. Their findings showed that humidity effects depended on polymer and solvent properties. They also showed the value of reporting viscosity. Concentration alone gives a less useful account of the process.

For a factory trial, record how viscosity was measured. Include the test temperature with the result. A number taken under different measurement conditions may not be a fair comparison. Include preparation date, mixing history, storage conditions and any change made before use.

Record the conditions at the process

Humidity and temperature readings should describe the region where the fibres form. A wall-mounted room sensor may not represent the air inside an enclosed machine. Record the sensor location and the period covered by its readings.

Avoid a rule such as “higher humidity always makes thicker fibres”. The study above found different responses across its polymer systems. Use a controlled trial to find how your material responds on the equipment being assessed.

Changing voltage, liquid delivery and collection distance at once makes the result hard to explain. A setting may work with one set of conditions. Check it again when those conditions change.

Include the support in the process record

Elmarco describes the variables in its Nanospider process. These include the solution, surrounding air, base material and equipment. It also describes drying and adhesion equipment around the spinning stage. These claims describe the maker's own system. They do not guarantee the same results from every spinning route.

The practical implication is to qualify the complete material path. Record the carrier's lot and treatment. Add the layer details, drying conditions and winding history. If the support changes, check whether the earlier result still applies.

Use defects to guide an investigation

A defect is an observation before it is a diagnosis. Photograph it, identify its position and compare it with the run record. Then decide what evidence would distinguish the possible causes.

Use these questions to guide the investigation. Each feature may have more than one cause. For example, a smooth area could be a useful dense structure or an unwanted fused patch. Its meaning depends on the product brief and the evidence from the process.

Do not select a corrective machine setting from the photograph alone. Use the approved trial procedure and change plan. Keep the failed specimen, its location and the original readings. They provide a clear basis for the next comparison.

Measure the distribution, not one attractive fibre

A diameter report should state how images and measurement locations were selected. Include the microscope calibration basis, specimen preparation, magnification and measurement rule. Clearly identify features that were excluded and why.

Measure across planned locations, including relevant width and length positions. Taking many measurements from one image gives detail about that image. It does not create independent evidence about an entire production roll.

The following tiny, fictional sets illustrate why the mean alone is weak evidence. They are not a proposed sampling plan.

Both sets have the same mean, but set B contains a much wider spread. Its 600 nm value should not vanish merely because the average looks good. These five values still tell us little about the whole roll. They cannot establish its defect rate or reliable extreme values.

For a real study, choose a suitable sampling plan before viewing the results. Show the distribution and the number of independently sampled regions. Label repeat measurements from the same region clearly. They do not count as separate rolls.

Also record features that diameter alone misses. These include beads, holes, fibre alignment, fused contacts and any damage from specimen preparation. Show both the numerical result and what the measurement can tell the reader.

Separate layer mass from the carrier

ISO 9073-1:2023 covers mass per unit area of nonwoven fabrics. Its public scope identifies what is measured. A formal test needs the full method. For a supported layer, also agree how the test will treat the layer and carrier.

The mass of a light layer can be small beside the support. Suppose a fictional 0.01 m² specimen has a layer add-on of 0.30 g/m². The layer contributes only 0.003 g, or 3 mg. If the carrier contributes 30 g/m², its mass in the same area is 0.300 g.

The finished specimen therefore contains 0.303 g before any other additions. A carrier difference of just 1 g/m² would change that specimen's mass by 0.010 g. That is more than three times the intended layer mass.

Subtracting a nominal carrier value may give a misleading estimate of layer mass. Agree a sound method for comparing the samples. Account for support variation, conditioning and what the measurement can resolve. Do not assume that removing a layer leaves both materials unchanged.

The balance must suit the difference being measured. A display that changes in 0.01 g steps moves by 10 mg at a time. The example's 3 mg layer is smaller than one display step. A plausible total reading would not prove that this small add-on had been measured reliably. A different specimen size or test approach may be needed. Assess whether it can resolve the difference before use.

Keep the raw mass readings and the calculation together. Identify whether support specimens came from the same roll and nearby positions. Explain how moisture and retained solvent were handled. If you subtract two readings, assess the uncertainty of their difference. The precision of each displayed number is only part of that question. Adding decimal places in a spreadsheet cannot recover missing measurement data.

ApparelDiary's fabric GSM and roll-weight guide explains the general area and mass relationship. Here, the main challenge is to establish which material has been weighed.

Calculate output from dry polymer to accepted area

Liquid feed rate is not finished fibre output. First identify how much dry polymer enters. Then distinguish collected polymer, accepted layer and elapsed production time.

Assume a fictional trial feeds 0.50 kg of solution per running hour. Polymer is 12% of the total solution mass. No other solids contribute to the measured layer.

Polymer feed = 0.50 kg/h × 0.12 = 0.060 kg/h = 60 g/h.

The remaining solution mass is 0.44 kg/h. That figure describes the input balance. It does not mean all solvent evaporates at once. It also cannot, on its own, establish the required exhaust capacity.

Suppose 75% of the polymer reaches the intended carrier as dry material. Collected polymer is 60 × 0.75 = 45 g/h. Account for the other 15 g/h. Include measured losses and any change in material held within the system.

Now assume a uniform layer at 0.30 g/m² on a 0.50 m coated width. Ignore edge trim for this illustration. The gross area rate supported by the collected polymer is:

Gross area = 45 g/h ÷ 0.30 g/m² = 150 m²/h.

That corresponds to 150 ÷ 0.50 = 300 running metres per hour, or 5 m/min. The calculation gives a mass-balance limit under the assumptions. It does not prove that drying, collection or winding can achieve that speed.

Suppose 80% of the gross area passes the agreed product tests. Assume the accepted and rejected areas have the same layer mass per area. Accepted output is 150 × 0.80 = 120 m² per running hour. Its polymer mass is 36 g/h, with 9 g/h in the rejected area.

The accepted length is 240 m per running hour. Expressed as an equivalent rate, that is 4 m/min. The actual web still runs at the assumed 5 m/min; the lower figure accounts for rejected material.

If the machine runs for six hours in an eight-hour scheduled shift, accepted output is 720 m². Dividing by all eight scheduled hours gives 90 m²/h. Quoting 150 m²/h as saleable shift capacity would ignore both quality losses and stopped time.

Finally, suppose the required add-on doubles to 0.60 g/m² while collected polymer remains 45 g/h. Gross area falls to 75 m²/h, equivalent to 2.5 m/min at the same width. Check quality yield again. The thicker layer may behave differently from the first one.

Check what a scale-up claim actually measures

When reading an experiment, keep its material, method and result together. One favourable number can mislead when taken out of that context.

In Gilmore and Gouma's 2024 study, a high-throughput system produced about 2.6 g/h. The trial used the study's PVP and ethanol formulation. That was about fifteen times the flat-plate comparison. Yet the high-throughput system gave an average fibre diameter of about 2,595 nm. The flat-plate setup gave 643 nm.

The result demonstrates a trade-off in those experiments. It does not show that every high-output system makes thick fibres. Nor does it establish the output for another polymer. The authors also discuss collection losses and differences among the tested geometries.

For a supplier trial, ask what was weighed, over which period and after which drying step. Check how the rate treats warm-up, cleaning and roll changes. Ask whether it includes rejected area or carrier mass. Request the measured diameter distribution and full-width output from the same run.

Scaling a small device's output by the proposed number of units gives a planning estimate. Test that estimate on the combined system. Shared drying, material supply and later handling can limit the whole line. Each spinning unit may still run well on its own.

Match each claim to the right test

A layer may be intended for filtration, clothing or another technical use. The acceptance test must address the intended claim on the relevant material state.

For airflow through fabric, ISO 9237:1995 covers air permeability. Its scope includes nonwovens. Air permeability is not a particle-removal result. Use matched test conditions to compare materials. Describe their supports clearly as well.

For flat-sheet filter efficiency, consider ISO 29463-3:2011. It belongs to a wider series for high-efficiency filters and filter media. Select the applicable procedure with the laboratory. Passing a sheet test does not qualify a finished filter assembly or a respirator on its own.

For clothing layers, ISO 11092:2026 addresses thermal and water-vapour resistance. It uses steady conditions and includes multilayer assemblies. Its scope explicitly separates the test conditions from specific comfort situations. Air permeability cannot stand in for water-vapour resistance. Neither result alone proves wearer comfort.

Test the material after the steps that it will actually experience. Lamination, flexing, cleaning and storage can be part of the agreed qualification plan. State the treatment and specimen state beside each result. Explain any comparison between an untreated laboratory layer and a finished assembly.

Build a trial that can support a production decision

Start with the product question. Define the required layer, support, dimensions and intended use. Agree what to measure and how to judge it. Set the conditioning basis before selecting the best-looking result.

Next, establish a baseline. Use a documented material batch and a stable approved process, then retain the samples. Check that the first trial can be repeated before changing it. Otherwise, later comparisons may rest on an unreliable reference.

Plan each change so that its purpose is clear. Where several factors need to be studied together, use an appropriate experimental design. Keep track of process changes. Also mark any change in polymer batch, support or measurement method so that their effects remain distinct.

Run long enough to investigate the questions in the brief. A short stable period may answer whether fibres can form. It may not show how solution condition changes during a full run. Nor will it establish that width uniformity and collection yield remain acceptable.

Finally, link the accepted material to its cost. Include solution preparation, carrier, drying, handling, testing, stopped time and rejected output. Calculate cost per accepted square metre on the specified material basis. Compare that with the required volume and the evidence for repeatable performance.

Include operating controls in the feasibility review

High-voltage equipment, solvents and released material need a process-specific assessment before a trial. Use the equipment maker's approved procedures. Have competent engineers review electrical protection, ventilation and access. A published fibre photograph does not supply those operating requirements.

NIOSH gives guidance on downstream nanomaterial processing. It stresses the need to design and test controls for the actual process. It also highlights maintenance and access needs. This is general exposure-control guidance, not a design certificate for an electrospinning installation.

Assess the normal run as well as other tasks. Include cleaning, changing material and removing collected waste. The control plan must cover solvents as well as particles. A particle filter does not establish control of solvent vapour. Review the chemical information using the safety-data-sheet guide for trials.

Questions worth asking before approval

Is a lower mean diameter always better?

Only if it helps meet the actual product requirements. Check the full distribution, layer integrity and relevant performance tests. A smaller mean that comes with poor yield or damage may be a worse production choice.

Can a laboratory recipe be transferred unchanged?

Treat it as a starting point for controlled development. Confirm material grades, measurement methods, environment, geometry and downstream steps. Matching a concentration alone does not establish equivalent conditions.

What is the most useful capacity figure?

Use accepted output per scheduled hour. State the width, add-on and product tests that define this output. Keep the underlying running rate and losses visible. This makes the estimate usable for both planning and cost comparisons.

What should a release package contain?

Include traceable material and process records. Add the sample plan and its basis, test results, loss accounting and the limits of approval. Link the fibre images to the accepted roll and its intended use. That link helps production act on the trial results.

References

• Reneker et al.: Bending instability of electrically charged liquid jets of polymer solutions in electrospinning.

• Nezarati et al.: Effects of humidity and solution viscosity on electrospun fibre morphology.

• Gilmore and Gouma: Scalable electrospinning using a desktop, high-throughput, self-contained system.

• Elmarco: Nanospider technology and associated equipment.

• ISO 9073-1:2023: Nonwoven mass per unit area.

• ISO 9237:1995: Fabric air permeability.

• ISO 29463-3:2011: Testing flat-sheet filter media.

• ISO 11092:2026: Thermal and water-vapour resistance.

• NIOSH Publication 2018-122: Protecting workers during intermediate and downstream processing of nanomaterials.