Control of Electrospun Jets Instabilities:In Pursuit of Perfect Continuous Nanofiber Alignment

Abdelrahman R.M Elsayed Author

04/02/2021 Added

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UNL Research Fair spring 2021

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[00:00:00.820]Hi, welcome to my presentation
[00:00:03.280]for the UNL Research Fair.
[00:00:07.250]My name is Abdelrahman Elsayed,
[00:00:09.000]and I'm a senior mechanical engineering student.
[00:00:11.600]And I worked in Dr. Dzenis lab.
[00:00:13.850]Today, my presentation is about, continuous nanofiber.
[00:00:23.850]So in the last century, and with our humanity advancement,
[00:00:29.000]we are in need of new materials.
[00:00:31.750]Materials that are lighter and stronger,
[00:00:34.740]and can help us to save energy
[00:00:37.420]and can help us with many structural applications.
[00:00:43.060]One of the materials that has been developed
[00:00:45.580]in the last century is composites.
[00:00:47.960]And especially carbon composites.
[00:00:51.140]Carbon composites are using so many applications,
[00:00:53.320]especially in the airspace, structure application
[00:00:57.250]and they're used as well in protective clothing
[00:01:00.070]and entertainment and automobile manufacturing.
[00:01:03.550]And as you can see in this graph,
[00:01:06.710]the market for the composites overall
[00:01:09.110]and carbon fiber specifically,
[00:01:11.860]has been growing for the last five years
[00:01:14.670]and will continue growing in the next decade.
[00:01:20.140]In our research group in the last 10 years,
[00:01:24.100]we have been working on developing
[00:01:26.410]carbon fiber to be stronger,
[00:01:29.130]and to have like more strengths.
[00:01:31.440]So we have discovered that decreasing the fiber diameter
[00:01:37.570]will significantly increase
[00:01:39.660]the strengths, modulus and toughness.
[00:01:42.520]And as you can see in the graph to the right,
[00:01:45.570]the strengths and the modulus of the fiber
[00:01:49.550]increased dramatically with decreasing the fiber diameter
[00:01:53.800]to like several nanometers.
[00:02:02.832]And this process is done by electrospinning,
[00:02:06.280]which I will explain later.
[00:02:07.980]But as you can see on the figure to the left,
[00:02:10.160]decreasing the diameter of the fiber
[00:02:12.240]will also not only increase the strength and modulus
[00:02:17.570]but will increase the toughness as well.
[00:02:21.810]So the electrospinning process
[00:02:23.250]which is made to make nano fiber is pretty simple.
[00:02:26.920]You have like the polymer
[00:02:30.410]that you are spinning the fiber from,
[00:02:32.580]and you put it in a syringe,
[00:02:33.930]and you apply a voltage between the syringe and a collector,
[00:02:38.370]and like the fiber start coming.
[00:02:40.290]As you can see in the photo to the left,
[00:02:43.170]the fiber comes as a jet.
[00:02:46.750]And this jet is collected on this collector.
[00:02:49.750]The challenge with the electriospinning,
[00:02:52.217]is the instabilities that comes
[00:02:54.770]with the polymer solution electriospinning.
[00:02:57.460]So as you can see when the fiber comes out,
[00:03:00.500]it doesn't come out align, but it comes out
[00:03:03.310]in this wavy shape, which have two sets of instabilities.
[00:03:09.010]This instability causes the fiber to be disalign,
[00:03:12.290]which means it cannot be used in many applications
[00:03:15.810]that requires the fiber to be aligned
[00:03:17.950]to have the maximum strains.
[00:03:21.460]On my research, I've been studying different parameters
[00:03:25.050]that affects the fiber alignment and try to optimize them.
[00:03:28.350]And this parameters includes the RPM,
[00:03:31.260]which is the speed of rotation of the collector,
[00:03:35.680]the voltage, which is the applied voltage
[00:03:37.740]between the syringe and the collector,
[00:03:46.966]the substrate width of the collector
[00:03:50.630]that I'm collecting the fiber on,
[00:03:52.510]as well as the duration of the spinning.
[00:03:55.730]My goal was to conduct several experiments
[00:03:58.950]and see how changing in these parameters
[00:04:01.410]will change the alignment of the fiber
[00:04:03.310]and how to get the best alignment.
[00:04:05.400]I was only also focusing on studying
[00:04:08.290]the diameter distribution of the fibers,
[00:04:11.140]with changing these parameters as well.
[00:04:13.720]And as you can see here in the first study,
[00:04:16.770]I've been working with changing the RPM
[00:04:19.260]like to a different number between 2000 and 10,000 RPM.
[00:04:24.240]And it has been noticed that increasing the RPM
[00:04:27.700]significantly affects the alignment.
[00:04:29.960]As you can see, in the photos to the left,
[00:04:32.400]with increasing the RPM, the fiber gets more aligned.
[00:04:36.200]And from the graph you can also tell
[00:04:37.990]the fiber diameter decreases with increasing the RPM.
[00:04:48.370]The next study is studying the polymer concentration
[00:04:53.100]on affecting the fiber alignment.
[00:04:56.480]And as you can see, increasing the polymer concentration
[00:04:59.780]have increased the fiber alignment.
[00:05:03.450]And I've done several experiments
[00:05:07.220]seeing how the the concentration
[00:05:09.240]affecting the diameter as well.
[00:05:11.850]And like the data didn't give us any trend about
[00:05:14.770]how the concentration affects the diameter,
[00:05:18.850]but we can say from like the experimental data
[00:05:23.540]that I got through the imaging, the microscope imaging,
[00:05:28.330]that the alignment have increased
[00:05:30.510]with increasing the PAN concentration
[00:05:32.620]which is the polymer used in the electrospinning process.
[00:05:38.630]The next study focused in the duration of the spinning
[00:05:41.860]and the duration of the spinning,
[00:05:43.010]I have a start spinning from like 15 minutes
[00:05:47.120]up to 115 minutes.
[00:05:50.850]And as you can see the spinning as you go more in time
[00:05:55.960]and increase the time of the spinning,
[00:05:57.890]the fiber alignment decreases.
[00:06:00.800]And we have concluded that,
[00:06:02.400]this is because of the buildup,
[00:06:04.020]a charge on the fiber accumulated over time.
[00:06:09.660]We have also conducted a study on the substrate width.
[00:06:12.450]And we have focused here in studying this
[00:06:14.730]with different RPM.
[00:06:16.290]So I (indistinct) like 3300s RPM and 8700s RPM.
[00:06:22.350]And as you can see, as the substrate width increases
[00:06:28.020]the fiber alignment decreases for both speeds.
[00:06:34.740]The last study focused on the voltage effect
[00:06:37.530]on fiber alignment.
[00:06:39.090]And we also studied the diameter
[00:06:41.020]how the voltage affected diameter.
[00:06:43.780]So as you can see, as the voltage increased,
[00:06:49.780]it reached to the point where there's the perfect alignment
[00:06:53.140]and as it increases more alignments gets worse.
[00:06:56.510]So we have concluded that the between nine and 10 voltage
[00:06:59.650]is the best voltage to do the electoralspinning process.
[00:07:03.470]The diameter also decreases significantly
[00:07:06.310]with increasing the voltage.
[00:07:10.600]That's my study for electrospinning,
[00:07:13.060]thank you for watching,
[00:07:14.380]and I want to thank UCARE program
[00:07:18.190]and Nebraska Center for Energy Sciences Research
[00:07:21.040]and Joan Williams foundation for supporting my research.

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Control of Electrospun Jets Instabilities: In Pursuit of Perfect Continuous Nanofiber Alignment

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Control of Electrospun Jets Instabilities:In Pursuit of Perfect Continuous Nanofiber Alignment

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