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

Abdelrahman R.M Elsayed Author

04/02/2021 Added

12 Plays

Description

UNL Research Fair spring 2021

Searchable Transcript

Search:

[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.

The screen size you are trying to search captions on is too small!

You can always jump over to MediaHub and check it out there.

Comments

0 Comments

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

Description

Searchable Transcript

Comments icon comment

Related Channels

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

Comments