Week 9 - If There Was a Re-experimentation...

If there was more time to experiment and design the other variables related to electrospinning. A possible variable to test would be the concentration of the solution on diameter length of the fibers and see if the results match that of literature from scholars. Another aspect could be to use a different polymer and create a solution that would have different affects on fiber structure and other properties. The final characteristic we would like to do is test fibers that we spin with a tension meter and other forms of strength testing.

Week 8 Cont. - Final Results/Conclusion

The purpose of this experiment and design is to create a minute filter that will trap bacteria in contaminated water flow. The actual testing of the filter will be the different variables that are present in the spinning of the fibers that compose the filter. The two variables that were tested was the distance between the syringe to the collecting plate and the angle between the syringe and the collecting plate. The results below show the outcomes and final conclusions.

Because the smallest common bacteria found in contaminated water flow is Fecal Coliform, the diameter of the fibers must be less than the length and therefore the volume of the bacteria. The length of this bacterium is 600 to 700 nm. When testing the distance variable, the smallest diameter of the fiber with a low standard deviation was spun at 12 cm. The average diameter of 30 fibers measured at 12 cm was 49.52 nm with a standard deviation of 14.39 nm. Another observation noted that was seen through the SEM images at 12 cm was the decreased number of beads that formed. All of the other distances had an abnormal number of beads in comparison to the aforementioned distance. The second variable involved the angle between the syringe and the collecting plate. The smallest diameter of the fiber was found at 20° and a standard deviation. The diameter was 52.71 nm while the standard deviation was 13.30 nm. Therefore, 20° will be the chosen angle for the final spin.

Final Conclusion:

In order to spin the smallest size diameter, the results show that the solution being spun should be spun at 12 cm from the collecting plate and at an angle of 20°. In order to create viable fibers to create a filter, another solution must be made and follow the specified variables above.

Week 8 - Analyzing SEM Images 2 (angles)

In week 7, the microfibers were spun at different angle measurements in 10° increments. The angles were 0, 10, 20, 30, 40, and 50. Through these angle measurements there were 5 samples spun. The 50° angle did not spin correctly so the samples show the angles 0-40 in 10° increments. This was done for the same goal as the samples spun in week 4.


PEO- 0°

Figure 27. PEO at 0° 

The sample of PEO spun at 0° is illustrated in Figure 27. This image is zoomed to make calculating the distances easier. Using ImageJ 30 different threads were measured and the average of the threads were 59 nm. The standard deviation was 0.01 µm.  














PEO- 10° 

Figure 28. PEO at 10°

Figure 28 shows a bundle of nanofibers. Using the ImageJ measuring tool. The average of these nanofibers were 54 nm, and the standard deviation was 0.017 µm. This measurement is very similar to the measurements at 0°. the standard deviation is a little higher than at 0° which means there might have been more human error. The measurement regarding the averages were only 5 nm off.








PEO - 20°s

Figure 29. PEO at 20°

Figure 29 is PEO spun at 20°. The measurements were only taken from 28 different nanofibers to avoid duplicate measurements. The average of the measurements was 52.71 nm, and the standard deviation was 0.0133 µm. This is 2 nm off from the average from 10°.











PEO - 30°

Figure 30. PEO at 30° 

Figure 30 is PEO spun at 30° and seemed to have the most fibers spun in all the images. The measurements were taken from 30 fibers and the average was 58.37 nm. The standard deviation was 0.015 µm. This measurement is 1 nm off from 0°, 4 nm from 10°, and 6 nm off from 20°.










PEO - 40°

Figure 31. PEO at 40°

In figure 31, spinning did not produce many fibers in this picture. However, There are approximately 35 different fibers in the picture. Because of this only 25 Threads were taken into account to reduce the chance of duplicating a nano fiber. The average of the measurements were 54.19 nm. The standard deviation was 0.014 µm. This measurement is very similar to the measurements done at the alternate angles.









The diameters of the fibers spun at the various angles showed that the angle at which the fibers are spun have little or no effect on the diameter of the fibers. The fiber diameters are very similar and human error as well as mechanical error could explain how the measurements vary. The fiber spun at 20° has the lowest diameter size as well as the second lowest standard deviation so 52.71 nm will be the lowest average diameter among all the possible angles. Therefore, 20° will be the chosen angle for the final spinning.

Week 7 Cont. - Impact of Filter on Society

If our filter model works and the fibers inside the filter perform well by trapping the bacteria in water flow, then the major disease rates from contaminated water may go down. Diseases such as cholera which has over a quarter of a million reported incidents each year in China and India would not be as common [6]. In Africa, E.coli colonies are found in the water supply frequently and causes stomach issues as well as meningitis. With the lack of medical supplies and facilities in these three areas of the world, individuals residing in these areas are forced to endure the pain. The level of the disease could be so high that it is certain death if contracted from the water supply. This filter could potentially be the next big creation in filter engineering around the world that will once and for all eliminate impure water. If the cost to create this filter is low, they will be sold at a lower price; making it affordable to almost all classes (poor, middle, or upper class).

Why filtering is important?

Water purification is important because impurities are removed from water by screening, sedimentation, filtration, chlorination, or irradiation. Aeration saturates water with air, usually by spraying fountains of water into the air. Aeration removes odors and tastes caused by decomposing organic matter, industrial wastes, and some gases. These decomposing wastes and fecal matter is perfect for bacteria to grow and are easily transferred into the water flow. Various salts and metals cause hardness in water. Hardness may be removed by boiling, by adding sodium carbonate and lime, or by filtering through natural or artificial zeolites [2].

Week 7 - Results Analysis (1st Variable) and Taylor Cone

Figure 25. 3% PEO solution spun  at 10 cm [16]

A lab conducted by the Department of Electrical and Computer Engineering at the University of Waterloo had similar data and the engineers that conducted a similar experiment which had conclusions that mirrored ours. The SEM picture on the left shows a 3% PEO solution spun at a distance from 10 cm. The beading occurred just like in our 12 cm spinning. The fibers were at a similar length. The average fiber diameter for their experiment at this distance was 55.65 nm, while ours was 49.52 nm. They concluded that 10 cm had the least beads formed, had the right diameter fibers needs for the aliginate gel formation, and it was the most consistent with a standard deviation in diameter 9.87 nm. The beads formed because of a taylor cone and the voltage that ran through the solution.



Figure 26. Effect of voltage on Taylor Cone [16]



The voltage change drastically affects whether or not beads or fibers form. The lower the voltage, the more beads will form from the spinning. If the voltage is between 3 kV to 7 kV, there will be some beads and some fibers. If the voltage is above 7 kV, the jet will mostly form fibers. A Taylor Cone is a jet of charged particles that emanates above a threshold voltage. The name Taylor Cone is named after Sir Geoffrey Taylor whom in 1964 coined the term before electrospray was "discovered" [11]. As the voltage is increased the effect of the electric field becomes more prominent and as it approaches exerting a similar amount of force on the droplet as the surface tension does a cone shape begins to form with convex sides and a rounded tip.



Week 6 Cont. - Initial and Final Filter Designs.

 

Figure 21. Side view of preliminary filter design

 

Figure 22. Direct view of preliminary filter design



During week 6, Preliminary designs were created and a final design was chosen for the filtration system. The first filtration design is shown in figure 20 and 21. This design is called a mat pattern. There are many benefits to a this design but there are also some faults which became clear after extensive research about filters. The mat design of the filter consists of alternating vertical and horizontal nanofibers. This causes water to easily pass through the nanofibers while the bacteria will get caught in the matted net design. Through research that was conducted, it seems that the specific bacteria have the capability to pass through this pattern because the openings have a possibility of being too large (diagonally). This pattern creates little squares which can fit bacteria through and continue with the flow of water. As shown in figure 21 on the left, the pattern leaves openings big enough for water, as well as unwanted bacteria to pass through.  



Figure 23. Final filter design top view



Figure 24. Final filter design showing layers of nano fibers



After realizing that this design was faulty, the filter was redesigned into a spiral or helix shape. This design is seen in figures 22 and 23 to the left. The final filter designs have approximately 250 nanofiber sections in the cylindrical tube that turn at 5 degrees and move 20 μm inside the filter every section. This makes the filter a total of 5cm in length. This design is ideal for letting liquids pass through the filter and leaving any unwanted particles stuck in the filter. The design of this filter will also spin the nanofibers at a slow speed to insure that no unwanted particles will pass through the cracks. The bacteria that resides in the water or other liquid will not be able to pass through due to the small openings in the filter. The initial filter design was a static design only made as a net that would trap particles and bacteria. With this filter design, The nano fibers are perfectly aligned with each other and the separation between each nano fiber is approximately less than 0.6 μm due to the movement and alternating fiber displacement of the filter. These values were outputs that Pro/E measured in the filter design.This number was chosen because it is the smallest size of the bacteria in cubic μm. This filter is the ideal chosen to block bacteria such as  E. Coli and Giardia cysts.  

Week 6 - Competition is Met, Why We Stand Out

If the design goal was met and the filter was actually created, the filter would be put into the market for consumers to buy. However, there are many other individuals who use nanofibers to create their own specific types of filters to accomplish the same exact design goals we have! So what sets this apart from large companies such as United Air Specialists Inc., Calibex, or even Donaldson [15]?

Figure 18. Filters used to trap smoke and allergens [3]

United Air Specialists mainly focus on nanofibers spun implemented in filters for domestic usage. The company provides solutions to air quality problems ranging from welding smoke, oil mist and process dusts in factories to indoor air quality concerns like cigarette smoke and allergens in offices, bars and homes [15]. The product that we are creating will focus on molecular substances that cause disease on the nanoscale level. United Air Specialists have very large filters used to trap macromolecules. The picture on the right shows the size of the filters and the design. The central core is put into a rotating device so the molecules that are trapped by the filter are evenly spread out through the cylindrical surface. The filter that will be inside of the core and there will be several layers of patterned fibers that will trap the bacteria. The chosen design is the best choice because it completes the overall design goal in preventing bacteria to stay in the water flow.

Figure 19. Calibex fibers (1 micron) [1]

Calibex and Donaldson are similar in the sense that they deal with a wide range of filters. Some types of filters are: electronic, digital, mechanical, optical, and of course fibrous. Calibex filters that are made from nanofibers are similar to the fibers that we will be using in our theoretical filter. There are only two major differences. One deals with the fiber size. Calibex fibers are 1 μm in diameter which is about 15 times larger than our filters; however, our diameter is really inconsistent. The other difference is the usage of the filter.the function it is being used for is water treatment, but the filters that Calibex makes are mostly for oil particle absorption and smoke filtering. Donaldson uses smaller diameter fibers ranging from 100 nm to 150 nm [15]. Their design is similar to ours in the sense that they use the fibers in layers to create a filter. However, they have no specific design and randomize the fiber layout. The plan is to create a filter that also has many layers of fibers but are in a specific pattern (square-like shape).

Figure 20. Donaldson fibers 100 nm [2]

This filter is the best choice because the shape is what distinguishes it from the other types of filters and brands. The prices of the filters above ranged from $50.00 to $179.99 [15]. There is no specific price of the completed electrospun filter for the time being, but theoretically, it should fall in that range.