Frequently Asked Questions

Qn 1-1. My solution is not spinning fibers, how do I solve this?

Ans: The first step is to check whether the solution is conductive. If the solvent used is non-conductive, you may dope it with solvent such as dimethylformamide or methanol. If this is not the issue, increasing the concentration or use a higher molecular weight polymer. However, increasing the concentration or increasing the molecular weight would also increase the fiber diameter.

If the substance used to spin the fiber is fixed, you may blend it with a polymer that is spinnable. Otherwise, you may use a core-shell spinneret setup where the one of the components is spinnable.

Qn 1-2. I'm getting beaded fibers, how do I solve this?

Ans: The most straight forward way is to increase the concentration or increase the molecular weight of the polymer. However, do note that this would also increase the fiber diameter.

Another way is to use a solvent that is more conductive or dope the solution with a more conductive solvent or add salt to it.

Adjusting the voltage, spinneret tip-to-collector distance, reducing feed-rate and reducing the humidity may decrease the number of beads if it is not serious.

Qn 1-3. How do I reduce the fiber diameter?

Ans: The first attempt is to reduce the concentration of the solution until beads start to appear. Use a more conductive solvent or dope the solution with a more conductive solvent or add salt to it.

Adjusting the voltage, spinneret tip-to-collector distance and reducing feed-rate may also decrease the fiber diameter but this is usually less significant.

Qn 1-4. How do I spin a material that has low molecular weight?

Ans: Increase the concentration of the material. If it is still not spinnable, try blending with another spinnable polymer or use a core-shell spinneret setup where the one of the components is spinnable.

Qn 1-5. What are the materials that can be electrospun into nanofibers?

Ans: Generally, polymers are the most commonly used class of materials that are electrospun. Polymers are often dissolved in a conductive solvent for electrospinning although efforts are underway to fine tune electrospinning of polymer melts to give nanofibers.

Ceramic and metallic nanofibers can also be fabricated from electrospun nanofibers but post-spinning process is required.

Qn 1-6. My fibers are fused, how do I solve this?

Ans: Increase the distance between the spinneret tip-to-collector so that the solvent in the electrospinning jet has more time to vaporise. Otherwise, use a more volatile solvent.

Qn 2-1. How do I get aligned fibers?

Ans: There are several well-established methods of getting aligned nanofibers in electrospinning. The most commonly used method is to use a rotating collector through mechanical winding of the fiber. In particular, using a knife-edge disk collector is able to get better fiber alignment. Another method is to use a pair of parallel electrodes such that the nanofibers bridging the gap is aligned perpendicular to the edge of the electrode.

It is also possible to use auxiliary electrodes to steer the electrospinning jet such that the fibers are aligned.However, this method is likely to be slower than using the above mentioned methods and it would require rapid deflection of the electrospinning jet. You may find more details in my review paper, W.E. Teo and S. Ramakrishna (2006) A Review on Electrospinning Design and Nanofibre Assemblies. Nanotechnology vol. 17 pg. 89-106.

Qn 2-2. How do I spin a 3D nanofibrous structure?

Ans: There are several methods of getting 3D nanofibrous structure. One way is to use a dynamic flow method described in this link.

Another method is to collect the fiber on a low-surface tension solvent such that the fiber sinks below the liquid surface as it deposits. Spinning a thin layer of nanofibers and crushing it is also another simple way of getting 3D nanofibrous structure.

You may find more details in my review paper, Wee-Eong Teo, Ryuji Inai and Seeram Ramakrishna. (2011) Technological advances in electrospinning of nanofibers. Sci. Technol. Adv. Mater. vol 12 pg. 013002. Open Access

Qn 2-3. How do I spin nanofibrous yarn and what is the current production rate?

Ans: There are currently several methods for spinning nanofibrous yarn. One way is to use a dynamic flow method to draw deposited nanofibers on a water surface into a yarn (See link).

The fastest yarn spinning reported in literature is from self-bundling of electrospun nanofibers in the air (during electrospinnnig) and drawing the bundled nanofibers into yarn at a speed of 894 m/min. However, similar mechanism has been attempted by other researchers but the yarn take-up speed is between 10 m/min to 45 m/min. The next fastest lab-scale yarn spinning speed is using the dynamic flow method at a literature reported speed of 63 m/min.

You may find more details in my review paper, Wee-Eong Teo, Ryuji Inai and Seeram Ramakrishna. (2011) Technological advances in electrospinning of nanofibers. Sci. Technol. Adv. Mater. vol 12 pg. 013002. Open Access

Qn 2-4. How do I control the electrospinning jet?

Ans: Generally, to control the electrospinning jet, it is necessary to tame the chaotic motion of the jet path. The stable portion of most electrospinning has a length of about 1 to 2 cm. Some researchers bring the collector to within this distance such that the deposition location can be determined with greater accuracy. However, this is not often feasible and the fiber may be wet upon impacting the collector.

Another way is to alter the solution property such that the electrospinning jet is more "stiff" thereby resisting bending instability. This way, the stable portion of the electrospinning jet can be extended and this would allow auxiliary electrodes to control the spinning jet.

You may find more details in my review paper, Wee-Eong Teo, Ryuji Inai and Seeram Ramakrishna. (2011) Technological advances in electrospinning of nanofibers. Sci. Technol. Adv. Mater. vol 12 pg. 013002. Open Access

Ans: Technically, it is possible to use electrospinning to deposit fibers on an insulated material as long as it has a sufficiently lower charge density or opposing charge to attract the electrospinning jet. However, the difficulty of using a insulating material for collecting fibers is that the electrospinning jet carries charges. Without an avenue to discharge the collected fibers, build-up of charges would cause on-coming fibers to be repelled.

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