Abstract
The main goal of this project was to make modifications to an electrospinning apparatus composed of K’Nex pieces to improve the safety, cost, and mobility of the design. The electrospinning device modified was used as a practical educational tool to introduce materials science to high school students. A gearbox was added to the initial design, enabling the electrospinner to run at different speeds. A customized well plate was designed using ProENGINEER software and rapid-prototyped by a 3D printer. A banana jack was integrated into the custom well plate design. The custom well plate made the electrospinner’s height adjustable and also made the electrospinner safer. Several nanofiber samples were produced with the modified electrospinner; these samples were analyzed using a scanning electron microscope. The fiber diameter and density of the samples were assessed to determine the effect of speed on nanofiber production. It was determined that fiber density was larger at higher speeds. Overall, the project was successful; the new design was safer, cheap, and also easy to assemble and disassemble. Also, it has the potential to be a great educational tool, allowing students to observe an electrospinning process and the effect of speed on nanofiber production.
The main goal of this project was to make modifications to an electrospinning apparatus composed of K’Nex pieces to improve the safety, cost, and mobility of the design. The electrospinning device modified was used as a practical educational tool to introduce materials science to high school students. A gearbox was added to the initial design, enabling the electrospinner to run at different speeds. A customized well plate was designed using ProENGINEER software and rapid-prototyped by a 3D printer. A banana jack was integrated into the custom well plate design. The custom well plate made the electrospinner’s height adjustable and also made the electrospinner safer. Several nanofiber samples were produced with the modified electrospinner; these samples were analyzed using a scanning electron microscope. The fiber diameter and density of the samples were assessed to determine the effect of speed on nanofiber production. It was determined that fiber density was larger at higher speeds. Overall, the project was successful; the new design was safer, cheap, and also easy to assemble and disassemble. Also, it has the potential to be a great educational tool, allowing students to observe an electrospinning process and the effect of speed on nanofiber production.
Introduction
Problem Overview
Materials science is a subject that is not typically discussed in a high school setting. As such, it would be beneficial for materials science departments at universities to demonstrate materials science concepts to high school students in order to generate interest in the field. One materials science concept that can be discussed with high school students is electrospinning.
Electrospinning is a process that utilizes liquid polymer to create nanofibers. A conventional electrospinning apparatus consists of a voltage source, a syringe filled with the liquid polymer, and a grounded metallic sheet to catch the fibers. Fibers are formed when the syringe is placed over an electric field. “When the voltage reaches a critical value, the electric field strength overcomes the surface tension of the deformed polymer droplet, and a jet is produced” [1]. As the electric field intensifies, the liquid polymer is drawn from the syringe and projected towards the grounded metallic sheet [1]. Eventually, the strands of liquid polymer on the metallic sheet dry, and the resulting strands of polymer, called nanofibers, can be used for various applications.
Dr. Jennifer Atchison constructed an electrospinner composed of K’Nex pieces as a demonstration tool for high school students. While the electrospinner properly displayed the concept of electrospinning, the device had a few technical problems that needed to be solved, including a bare copper wire, a non-stationary well plate, and only one speed setting. The main objective of this project was to optimize the pre-existing electrospinner. In particular, the model was modified to illustrate how speed affects the quality and quantity of the nanofibers produced. A custom well plate to hold the polymer being spun, as well as a conveyor belt to maximize the yield of the fibers were also considered for the final design.
Design Constraints
Several constraints for the overall design of the electrospinner existed. Since it was used as an educational tool for high school students, the electrospinner had to be produced at minimal cost. Furthermore, the electrospinner needed to be easily transported and reproduced. For these reasons, the majority of the electrospinner structure was restricted to K’Nex pieces. K’Nex pieces were relatively inexpensive items, can be purchased in bulk, and were relatively simple to take apart and reassemble.
Safety was another constraint on the design. The original design of the electrospinner consisted of an exposed copper wire used to charge the polymer; this caused a potential electrocution hazard. Since the electrospinner was operated by inexperienced students with minimal assistance, the modified design needed to avoid as many safety hazards as possible to ensure the students’ safety.
Pre-Existing Solutions
Several methods of electrospinning nanofibers already existed. The first method of electrospinning was the traditional electrospinning apparatuses, which made use of a syringe with a metallic needle to project polymer onto a grounded piece of metal [1]. Other existing systems, such as the Nanospider system produced by Nanoforce Technologies, utilized a turning wheel to collect the polymer [2]. The polymer is then pulled vertically up and collected on a grounded piece of metal project the polymer [2]. Both of these electrospinning systems are more suited for laboratory and industrial use largely because of their large monetary cost. As a result, electrospinning systems such as these were not readily accessible to public high schools for demonstration purposes.
The concept of a portable electrospinner for educational purpose had not been deeply explored. Dr. Jennifer Atchison was inspired to construct an electrospinner out of K’Nex pieces after observing an industrial model used by Nanoforce Technologies on the internet [2]. Since her design was only constructed with K’Nex parts, the design was easily constructed, cost-efficient and portable. The electrospinner had a low manufacturing cost and was capable of producing small amounts of nanofibers for demonstration purposes. However, the design was not a perfect solution and needed modification to make it safer and to help it display the effect of speed on nanofiber quality and quantity. Figure 1 features the original design of the K’Nex electrospinner created by Dr. Jennifer Atchison.
Problem Overview
Materials science is a subject that is not typically discussed in a high school setting. As such, it would be beneficial for materials science departments at universities to demonstrate materials science concepts to high school students in order to generate interest in the field. One materials science concept that can be discussed with high school students is electrospinning.
Electrospinning is a process that utilizes liquid polymer to create nanofibers. A conventional electrospinning apparatus consists of a voltage source, a syringe filled with the liquid polymer, and a grounded metallic sheet to catch the fibers. Fibers are formed when the syringe is placed over an electric field. “When the voltage reaches a critical value, the electric field strength overcomes the surface tension of the deformed polymer droplet, and a jet is produced” [1]. As the electric field intensifies, the liquid polymer is drawn from the syringe and projected towards the grounded metallic sheet [1]. Eventually, the strands of liquid polymer on the metallic sheet dry, and the resulting strands of polymer, called nanofibers, can be used for various applications.
Dr. Jennifer Atchison constructed an electrospinner composed of K’Nex pieces as a demonstration tool for high school students. While the electrospinner properly displayed the concept of electrospinning, the device had a few technical problems that needed to be solved, including a bare copper wire, a non-stationary well plate, and only one speed setting. The main objective of this project was to optimize the pre-existing electrospinner. In particular, the model was modified to illustrate how speed affects the quality and quantity of the nanofibers produced. A custom well plate to hold the polymer being spun, as well as a conveyor belt to maximize the yield of the fibers were also considered for the final design.
Design Constraints
Several constraints for the overall design of the electrospinner existed. Since it was used as an educational tool for high school students, the electrospinner had to be produced at minimal cost. Furthermore, the electrospinner needed to be easily transported and reproduced. For these reasons, the majority of the electrospinner structure was restricted to K’Nex pieces. K’Nex pieces were relatively inexpensive items, can be purchased in bulk, and were relatively simple to take apart and reassemble.
Safety was another constraint on the design. The original design of the electrospinner consisted of an exposed copper wire used to charge the polymer; this caused a potential electrocution hazard. Since the electrospinner was operated by inexperienced students with minimal assistance, the modified design needed to avoid as many safety hazards as possible to ensure the students’ safety.
Pre-Existing Solutions
Several methods of electrospinning nanofibers already existed. The first method of electrospinning was the traditional electrospinning apparatuses, which made use of a syringe with a metallic needle to project polymer onto a grounded piece of metal [1]. Other existing systems, such as the Nanospider system produced by Nanoforce Technologies, utilized a turning wheel to collect the polymer [2]. The polymer is then pulled vertically up and collected on a grounded piece of metal project the polymer [2]. Both of these electrospinning systems are more suited for laboratory and industrial use largely because of their large monetary cost. As a result, electrospinning systems such as these were not readily accessible to public high schools for demonstration purposes.
The concept of a portable electrospinner for educational purpose had not been deeply explored. Dr. Jennifer Atchison was inspired to construct an electrospinner out of K’Nex pieces after observing an industrial model used by Nanoforce Technologies on the internet [2]. Since her design was only constructed with K’Nex parts, the design was easily constructed, cost-efficient and portable. The electrospinner had a low manufacturing cost and was capable of producing small amounts of nanofibers for demonstration purposes. However, the design was not a perfect solution and needed modification to make it safer and to help it display the effect of speed on nanofiber quality and quantity. Figure 1 features the original design of the K’Nex electrospinner created by Dr. Jennifer Atchison.
Project Objective
The primary goal for the project was to optimize an electrospinner design composed of K’Nex parts to display the effects of the spinning speed on nanofiber quality and yield. The constraints of portability, cost, and ease of reproduction were fulfilled by constructing the main body of the electrospinner out of K’Nex pieces. This is primarily because K’Nex parts are easy to assemble and deconstruct and relatively low-cost.
The rest of the objectives dealt with modifications to the spinner and the well plate. Spinning the fibers at different speeds was desired. This was to be completed by creating a gearbox. The following three problems involved the existing electrospinner’s well plate. First, the original design included an exposed wire that carried current. This posed a potential electrocution hazard. Second, the well plate’s height, in relation to the rest of the electrospinner, was not adjustable. Because of this, it was not always easy to make sure the wheel picked up polymer. Third, the well plate was not fixed. As a result, the well plate was prone to moving around and caused a potential spilling hazard. These three problems needed to be solved by designing a customized well plate.
These goals were chosen based upon the time constraints and materials available. The project was unique from the other pre-existing solutions.
Technical Activities
Gearbox Design and Base Modifications
Over the course of ten weeks, the goal of designing an electrospinner for educational purposes had gone underway. One of the first key objectives was to allow the fiber to be spun at variable speeds. Along with the adjustments to the motor, modifications to the base of the electrospinner were considered. The design of the gearbox was simplistic. The intentions of the gearbox were for it to be easily assembled, thus allowing for ease maneuvering between the different speed settings. The gearbox allowed for options that were not previously available. By having various speeds, the user was able to determine the amount of nanofibers created. As shown in Figure 2, the gearbox was designed utilizing K’Nex pieces as an extension of the motor. One side of the motor was connected to a 1.9 cm diameter gear, and the other side was connected to a 4.9 cm diameter gear. Either side of the motor had been fitted with a different sized gear. By attaching the gears in different combinations, different speeds were achieved. This was done by attaching the gearbox to either side of the electrospinner, which provided a different ratio of the gear teeth and that allocated different speeds for the electrospinner.
The primary goal for the project was to optimize an electrospinner design composed of K’Nex parts to display the effects of the spinning speed on nanofiber quality and yield. The constraints of portability, cost, and ease of reproduction were fulfilled by constructing the main body of the electrospinner out of K’Nex pieces. This is primarily because K’Nex parts are easy to assemble and deconstruct and relatively low-cost.
The rest of the objectives dealt with modifications to the spinner and the well plate. Spinning the fibers at different speeds was desired. This was to be completed by creating a gearbox. The following three problems involved the existing electrospinner’s well plate. First, the original design included an exposed wire that carried current. This posed a potential electrocution hazard. Second, the well plate’s height, in relation to the rest of the electrospinner, was not adjustable. Because of this, it was not always easy to make sure the wheel picked up polymer. Third, the well plate was not fixed. As a result, the well plate was prone to moving around and caused a potential spilling hazard. These three problems needed to be solved by designing a customized well plate.
These goals were chosen based upon the time constraints and materials available. The project was unique from the other pre-existing solutions.
Technical Activities
Gearbox Design and Base Modifications
Over the course of ten weeks, the goal of designing an electrospinner for educational purposes had gone underway. One of the first key objectives was to allow the fiber to be spun at variable speeds. Along with the adjustments to the motor, modifications to the base of the electrospinner were considered. The design of the gearbox was simplistic. The intentions of the gearbox were for it to be easily assembled, thus allowing for ease maneuvering between the different speed settings. The gearbox allowed for options that were not previously available. By having various speeds, the user was able to determine the amount of nanofibers created. As shown in Figure 2, the gearbox was designed utilizing K’Nex pieces as an extension of the motor. One side of the motor was connected to a 1.9 cm diameter gear, and the other side was connected to a 4.9 cm diameter gear. Either side of the motor had been fitted with a different sized gear. By attaching the gears in different combinations, different speeds were achieved. This was done by attaching the gearbox to either side of the electrospinner, which provided a different ratio of the gear teeth and that allocated different speeds for the electrospinner.
Figure 2:
The gearbox attached to the base of the electrospinner
In order to attach the gearbox to the electrospinner, the base of
the electrospinner underwent slight modifications. The new electrospinner base,
Figure 2, had two opposing sides to which the gearbox was capable of being
attached. A similarity that the modified base shared with the gearbox was two
different sized gears attached on opposing sides; one side of the base had a
1.9 cm diameter gear and the other side had a 4.9 diameter gear. The addition
of these gears was crucial to allowing the speed of the wheel to vary. As
previously stated, different gear combinations allowed the wheel to run at
three different speeds: “slow,” “normal,” and “fast”. Equation 1 displays
the following calculations for the speed of the wheel. Table 1 displays
tangential speed of the wheel associated with speed setting.
Equation 1: The calculations of the tangential speed of each speed
setting
Table 1: Tangential
Speed of the Electrospinner wheel
Slow
|
Medium
|
Fast
|
|
Speed of Each Setting
|
3.597 cm/sec
|
9.050 cm/sec
|
20.525 cm/sec
|
In order to attach the motor to the base, slight modifications were made to the sides of the base. In addition to the modified sides, longer K’Nex pieces were used as the legs of the base.
Well
Plate Designs
Another major objective for the project was to solve the problems
that revolved around the well plate and the exposed copper wire used to charge
the polymer. The amount of polymer used for electrospinning was a problem
for the original design; the electrospinner overflowed if there was too much
polymer in the basin. In addition, no fibers were spun if there was not enough
polymer in the basin. Furthermore, the bare copper wire used to charge the
polymer was ill-secured on the existing well plate and often displaced itself
from the polymer. Once it displaced itself, the power supply had to be turned
off so that the copper wire could be re-secured in the well plate. The bare
copper wire was also very dangerous because the individuals operating the
electrospinner frequently were shocked when they were in close proximity to the
wire. To solve all of these problems, the group decided that a customized well
plate needed to be designed. The well plate had four rod holders that went
around the legs of the electrospinner base; this fixed the well plate on the x
and z axes, and allowed for the height variation along the y axis. The
adjustable height allowed the polymer to always reach the electrospinner. In
addition to the adjustable height, the well plate included a loop through which
the copper wire was fed. The well plate was designed using ProENGINEER
software. Once completed, the well plate was rapid-prototyped out of ABS
plastic by a 3D printer.
Figure 3 displays the initial design of the well plate. The
dimensions of polymer bed of initial well plate design were 12 cm by 11 cm.
When the well plate was attached to the electrospinner, the center
support rods were bent and the polymer bed was determined to be too large.
Furthermore, the wire loop in the initial design prevented the wire from
displacing itself from the polymer, but it had not removed the potential shock
hazard. To solve these problems, the well plate was redesigned.
Figure 3:
The rapid prototyped well-plate situated underneath the electrospinner design
The subsequent well plate design had fixed the problems of the
initial well plate. The rod holders were stretched by 1 cm so the well plate
aligned better with the electrospinner’s legs and the center supports no longer
bent. In addition, the dimensions of the polymer basin were reduced from 12 cm
by 11 cm to 9 cm by 9 cm. The safety issue was also fixed by increasing the
size of the loop and integrating a banana jack and plug as the power source
into the well plate. The banana jack had a copper wire soldered to its tip so
it could be placed in the polymer.
Testing the new electrospinner
The electrospinning apparatus used in the project differed from the conventional setup by using a polymer bed and wheel as the polymer source rather than a syringe. A voltage supply and grounded metallic sheet were still used in the K’Nex electrospinner. The mechanics behind the new electrospinner were the same as those involved in the standard electrospinning process; as the wheel spun, polymer droplets caught onto the thread strands of the wheel and were projected upwards due to the potential difference between the polymer and grounded sheet of metal. The beads of polymer were stretched and traveled in a spiral pattern until they reached the collection sheet.
The following conditions were constant for each sample of nanofibers spun. A 14 kV voltage was run through the polymer. The distance from the wheel to the collection sheet was 14 cm. The duration of each test was 20 minutes. After the electrospinner had spun for 20 minutes, each sample was then left to dry. Figure 4 displays the electrospinner wheel picking up the polymer.
Testing the new electrospinner
The electrospinning apparatus used in the project differed from the conventional setup by using a polymer bed and wheel as the polymer source rather than a syringe. A voltage supply and grounded metallic sheet were still used in the K’Nex electrospinner. The mechanics behind the new electrospinner were the same as those involved in the standard electrospinning process; as the wheel spun, polymer droplets caught onto the thread strands of the wheel and were projected upwards due to the potential difference between the polymer and grounded sheet of metal. The beads of polymer were stretched and traveled in a spiral pattern until they reached the collection sheet.
The following conditions were constant for each sample of nanofibers spun. A 14 kV voltage was run through the polymer. The distance from the wheel to the collection sheet was 14 cm. The duration of each test was 20 minutes. After the electrospinner had spun for 20 minutes, each sample was then left to dry. Figure 4 displays the electrospinner wheel picking up the polymer.
Figure 4 display an image of the electrospinner wheel working
The first samples
produced served as the control samples because they were created with the
original electrospinner design. All subsequent samples produced were spun at
various speeds with the modified electrospinner. These samples were analyzed
with respect to their fiber densities and diameters. Nine total samples were
spun in addition to the control samples. Three samples were spun for each wheel
speed.
After all of the nanofiber samples were successfully spun, the samples were
photographed using a scanning electron microscope (SEM). The SEM produces a
micrograph of a sample by scanning the image with a beam of electrons. Figures
6 and 7 display SEM micrograph of the nanofibers produced at the “slow” speed
setting and “fast” speed setting respectively.
Figure 6
(Left) and 7 (Right): Nanofibers generated on a “slow” and “fast” speed
setting, respectively
Results
The
nanofiber samples collected at each speed setting produced a unique set of
characteristics conditions. The medium speed served as an intermediate between
the “slow” and “fast” speed settings. It was visible that the fast speed
setting had generated the most nanofibers of the three settings during the
testing. The fast speed setting created the largest sample of nanofibers, in
both size and quantity. The amount of nanofibers generated was great enough to
cause excess polymer to form on the sides of the electrospinner. As the
electrospinner spun on the slow speed setting, there were no visible signs of
the fibers forming. Visibly, the slow speed setting did not generate any
visible signs of fibers being projected from the polymer.
Figure 6, shows that the nanofibers were fairly spaced apart and produced a significant number of beads when spun at the “slow” speed. Figure 7, the nanofibers spun at the fast speed setting were tightly knit and displayed no visible beads. Although these are preliminary results, these observations had proved that speed was factor in the formation of nanofibers.
Figure 6, shows that the nanofibers were fairly spaced apart and produced a significant number of beads when spun at the “slow” speed. Figure 7, the nanofibers spun at the fast speed setting were tightly knit and displayed no visible beads. Although these are preliminary results, these observations had proved that speed was factor in the formation of nanofibers.
Figure 8: Bar graph of the average nanofiber density; sorted by the
speed setting and runs
Figure 9: Bar graph of the diameters of the nanofibers generated; sorted
by the speed setting and runs
Fiber density and fiber diameter
were the two quantities analyzed in each micrograph. Figures 8 and 9 are graphs
organizing the fiber density and fiber diameter data collected from each
micrograph.
Upon analyzing the
samples, some trends were found. In Figure B, the average diameters for the
fibers in each sample spun are displayed. The data collected at the “slow”
speed was not very consistent. However, each “step”, in terms of speed,
increase caused the average fiber diameter to differ less between runs. Figure
A displays the nanofiber density for each sample; this data was much more
consistent. The “fast” speed had the highest fiber density and the “slow” speed
setting displayed the lowest fiber density. This was apparent visually from the
SEM micrographs; there are more nanofibers per unit area in Figure 7 than there
are in Figure 6. Therefore, both the consistency of fiber diameters and the
fiber density increase as the speed of the wheel increases.
Conclusion
The final deliverable of the project was a workable, cost
efficient, portable electrospinner. The electrospinner achieved all of the
desired goals. The final model included a gearbox that enabled the wheel to
spin at three different speeds. Furthermore, the gearbox allowed operators to
quickly switch between the different speeds by reconfiguring the gear ratio. In
order to make the design safer and more user-friendly, a customized well plate
composed of ABS plastic was created. This well plate replaced the plastic
sample cases used to hold the polymer in the original design. In order to
make the design safer, a banana jack was attached directly to the customized
well plate. This banana jack replaced the exposed copper wire used to charge the
polymer. Figure 10 displays the customized well plate with the banana jack. Furthermore,
the custom well plate attached directly to the electrospinner to prevent
accidental spilling of the polymer. This also allowed the height of the
rapid-prototyped well plate to be adjusted by sliding it up and down the legs
of the device according to how much polymer was in it. These modifications
achieved the goals of making a simple, low-cost electrospinner for
demonstration purposes.
Figure 10: The newly design well plate with the banana jack
As previously stated, the micrographs of the nanofiber samples showed that speed affected the quality and quantity of the nanofibers produced. As the speed of the wheel increased, the diameter of the nanofibers produced was more consistent and showed less beading. Also, as the speed of the wheel increased, the fiber density of the sample collected increased. The fact that this electrospinner shows variation in fiber characteristics due to speed is valuable in the classroom to illustrate the fact that there are various factors affecting the production of nanofibers. The final deliverable was a practical learning tool for a high school setting.
As previously stated, the micrographs of the nanofiber samples showed that speed affected the quality and quantity of the nanofibers produced. As the speed of the wheel increased, the diameter of the nanofibers produced was more consistent and showed less beading. Also, as the speed of the wheel increased, the fiber density of the sample collected increased. The fact that this electrospinner shows variation in fiber characteristics due to speed is valuable in the classroom to illustrate the fact that there are various factors affecting the production of nanofibers. The final deliverable was a practical learning tool for a high school setting.
Future Work
Despite the fact that the final deliverable is a practical electrospinner for a high school setting, further modifications could be made. For example, different types of polymer and metal collection plates could be used to determine how fiber quality and yield is affected. A miniature conveyer belt could be attached to the collection sheet of foil in order to get a longer continuous sheet of fibers. Testing could also be done to determine if a material would pick up and spin polymer more effectively than cotton thread. Implementing the electrospinner as a learning tool in a high school environment is also an important goal for the future. Instructions on how to construct the electrospinner will need to be created in order to implement this design as a tool for high school students. Using this electrospinner as an educational tool would allow universities and high schools to introduce and generate interest in materials science among high school students.
References
[1] Frank K., Ko (2005). Electrospinning [Database] Available:
http://www.accessscience.com/content.aspx?searchStr=electrospinning&id=YB052270
[2] Nanoforce Technologies. (2010 April 18). Electrospinning with Nanospider @ Nanoforce Lab [Video File]. Retrieved from http://www.youtube.com/watch?v=9_7bevTse4E
Despite the fact that the final deliverable is a practical electrospinner for a high school setting, further modifications could be made. For example, different types of polymer and metal collection plates could be used to determine how fiber quality and yield is affected. A miniature conveyer belt could be attached to the collection sheet of foil in order to get a longer continuous sheet of fibers. Testing could also be done to determine if a material would pick up and spin polymer more effectively than cotton thread. Implementing the electrospinner as a learning tool in a high school environment is also an important goal for the future. Instructions on how to construct the electrospinner will need to be created in order to implement this design as a tool for high school students. Using this electrospinner as an educational tool would allow universities and high schools to introduce and generate interest in materials science among high school students.
References
[1] Frank K., Ko (2005). Electrospinning [Database] Available:
http://www.accessscience.com/content.aspx?searchStr=electrospinning&id=YB052270
[2] Nanoforce Technologies. (2010 April 18). Electrospinning with Nanospider @ Nanoforce Lab [Video File]. Retrieved from http://www.youtube.com/watch?v=9_7bevTse4E
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