Does anyone know what these strange structures (A,B,C,D,E) could possibly be?
Some informations that might be useful:
-This is a PAN nanofiber mat (10%wt in DMF) that was electrospun with a NanoSpiderTM NS Lab 500 S (Elmarco s.r.o., Czech Republic) using a wire electrode.
-These SEM images were taken few hours after the mat was electrospun (-> There might still be some solvent in the mat)
-The same structures are also present in a mat electrospun months ago by another person in the same lab (this mat was vacuum dried for days). Since this mat was stored for a long time, I tought that these structures could be microorganisms. But if this was true, these structures shouldn't be present in the mat that was electrospun today.
I would appreciate any theories/ideas about what these structures could be.
Thank you!
Hi
This strange structure does not seem to be a microorganism and is related to droplets. These defects in nanofibers are generally observed due to the low concentration of the polymer solution or the short electrospinning distance. It may be possible to minimize these structures by changing electrospinning parameters such as increasing the electrospinning distance and using the optimal voltage, etc.
Good luck
Hi,
I agree with @alireza shaabani. In addition, the fact that the beads are usually formed at the surface indicates that the large amount of solution is thrown into the collector while stopping the device. For this reason, before stopping it (without turning off the voltage), place a cardboard at a safe distance between the collector and the cylinder. So you won't see the big beads visible on the surface.
Good work.
These look like artifacts. Any idea if the sample was dehydrated and then coated with metals and if so was it sputtered or evaporated in vacuum. If later is the case could it be oil vapors from the vacuum pump deposited on the film? Something to think about.
Aside from this, for good resolution of any sample under SEM please do not vacuum dry the samples but instead use HMDS for drying. CPD is another option but HMDS is simple, gives good resolution and doesn't require any equipment.
Best.....
Don't worry; neither a microorganism nor a noteworthy issue it is. This malfunction occurs in some mats, and almost everyone is dealt with it; these holes probably due to the drops, which can be related to the solution's low viscosity.
Seems defects in substrate/ base material used (if any). Yet another point to be considered is how high accelerating voltage (EHT) interacts with your material, so that no damage is being caused by Electron Beam while recording SEM images.
Thank you so much for all the answers!
It could be indeed droplets caused by the low voltage at the beginning and at the end of the spinning. The solution viscosity could also be the problem (I'll try to spin again with higher concentration). The distance shouldn't be the problem since I used the maximum distance possible.
Regarding the SEM, the samples were first dried for few hours at room temperature and then coated with gold. For the SEM image, I used very low voltage (5kV and spot 4). The next day, I did SEM images again of this sample after 24h in the vacuum dryer and the structure were still there.
I'll keep you updated as soon as manage to do produce mats without these structures :)
Sure it could be droplets caused by the low voltage at the beginning and at the end of the spinning.
Hello...
might be it's just a solution droplet. Try to increase the solution concentration.
these are the droplet of your electrospinning solution. this depends upon your solution viscosity, surface tension aa well as voltage and some time the environmental condition because some or say maximum time we are unable to maintain the ideal condition for electrospinning. So, not to worry, just change the viscosity of solution and measure surface tension to minimize the droplet deposition.
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