Wrapping Everything Up

We are now well into week 9 of this long project and everything has finally fallen into place. At this point we have successfully broken down all of the data pulled from the SEM images and formatted them into charts and graphs showing the accuracy and consistency of our results. These results can be found on our "Data Analysis" tab. We would have liked to get into the lab at least one more time to spin one more mat, but weather did not permit in the weeks that this could have happened. Luckily the data showed that the first mat spun yielded results very close to what we wished to achieve.

Last week we also received the great news that our project has been selected to receive funding from Air Products in Allentown, PA. This was a great honor to us and helped show that all of our hard work has payed off. We would like to thank Air Products once again for their funding, we are all very excited about this.

The group is now well into composing the Final Report and preparing for our Final Presentation that will be presented on Wednesday, June 6th. Carl will be organizing and annotating all sources that will be used throughout the report and presentation, as well as editing the final report. Richard will take care of the abstract, introduction section, and edit the final report. Abraham has prepared the Data and Results section. Kyle has taken on the responsibility of explaining the electrospinning process as well as a background on our project. Last, but not least, Gregory will explain future applications and show areas that this project can grow in the coming years.

Once the report is concluded, Carl will be preparing the final presentation and Abraham will be in charge of creating the IEEE poster to showcase our progress in this project. Be sure to stop by the Hill Conference Room at 2:00pm on Wednesday June 6th to view our final presentation of this 10 week process.

Interpretting and Plotting SEM Data

Last week, the images of the electrospun fibers was analyzed. From the image, more than 300 fiber diameter lengths were measured using the program ImageJ, as well as pore areas. Using Excel, and the scaling program on ImageJ, this data was converted into either nanometers, or nanometers squared, depending on whether it was a diameter length or a pore area.

For all the fiber diameter lengths, the mean value was calculated to be 108.2 nm, while the standard deviation was 30.5. For the pore areas, the mean value was 8.3 nm2 and the standard deviation was 5.75. Using these measurements and calculations, a table was created for both the diameter lengths and the pore areas and were put into percentiles of 10% differences between values. Using those percentiles, a normal distributive graph was obtained for both, allowing for the spread of the measurements to be illustrated. These tables and graphs, as well as a much more detailed explanation of the results, can be found on the "Data Analysis" page in the top navigation bar

The normal distributive graph for the fiber diameter lengths showed the even spread of the data, explaining the fiber diameter lengths can be within a certain range. The normal distributive graph for the pore areas illustrated that the majority of measurements were closer to the mean value, while there were a few rare large area pore. This showed the discrepancy between the fiber diameter lengths and the pore areas created by them, since the fiber diameter lengths were between a certain range, unlike the random pore areas.

SEM Images

The SEM images that were obtained are important for analyzing the mat. The SEM images that were obtained show that the first prototype was a success. Although the images show very distinct fibers, there are still certain abnormalities that were unavoidable.

Figure 1

Figure 2

Figure 3

Figures 1-3 show the successful images of the nano-fibers at 9000X maginification. These are the images that are being processed using the program ImageJ in order to complete pore size and fiber diameter analysis.

Figure 4 - Image of a spindle in the fiber

Figure 5 - Image of a beaded fiber

Figures 4 and 5 show abnormalities that occur when spinning a sample. Figure 4 shows a spindle which can be caused by numerous parameters such as humidity, voltage, flow rate, etc. Figure 5 shows a bead in the mat that can probably be associated with the machine turning off and on several times during the process, causing the polymer to bead up on the syringe. These can be caused by many other factors as well.

Analyzing SEM Data

Last week the group obtained micro-scale pictures of the lab sample with the Scanning Electron Microscope (SEM). Because the specimen is nonconducting, the sample was first prepared with a thin film of conducting material, like platinum, in order to reduce charging in vacuum conditions. This was accomplished using the Cressington Sputter Coater 208 HR. With Marjorie's help, the prepared sample was then viewed under the SEM. The microscope used was the Zeiss Supra 50VP.

(Left: Cressington Sputter Coater 208HR used for preparing the sample with a conductive film. Right: Zeiss Supra 50VP used view the sample.)

With pictures of the sample in hand, the group has moved into a phase of analysis. The images offer much insight on both the effects of certain spinning parameters as well as resulting filtration properties. In regards to the spinning (experimentation) component, the fibers produced appear consistent, almost entirely continuous and appropriately sized compared to the intended result. Further analysis of the fiber diameter and density will allow the group to improve the testing parameters for continued optimization. The group will also address a few unique cases of beads and spindles that were identified within the sample.

(Image of the group's sample at a scale of 2 micrometers and 5,000X magnification.)

In the analysis of filtration efficiency, the group must use imaging software to measure porosity of the sample. Using the program ImageJ, the SEM data can be analyzed by taking many appropriately scaled measurements of fiber diameter and areas of pores. For each of the samples, the average fiber diameter and average pore size will be quantified. In the analysis of average pore size, some constraints exist for this method of porosity assessment. In the sample images, there exists a certain degree of depth to which the scaling is appropriate for measurement. Moreover, fibers in the foreground of the image would produce a much larger average pore size than those in the back when under the same scaling. The group will address issue by using color analysis techniques in ImageJ.

Hold up in Week 5 and Analyzing the Mats in Week 6

Referring back to the electrospinning that took place in week 4, the mats were produced successfully by the use of a Harvard Apparatus Syringe Infusion pump (see figure 1). This machine had a syringe filled with our PEO solution that had a voltage source connected to the needle (see figure 2). The syringe spun the solution onto a sheet of aluminum foil for several hours. There were several small problems that occurred with the machine during this process; the machine kept shutting off every hour or two for unknown reasons. This made it very difficult to get the spinning done efficiently unless someone checked on it periodically throughout the process. After a full mat was finally spun, it was let to sit over night and then peeled free the next day.

Figure 1: Harvard Apparatus Syringe Infusion Pump used for spinning mat

Figure 2: Syringe for apparatus that held PEO solution with voltage source connected to needle

The plan was to analyze the mats under the SEM and determine what changes needed to be made to the parameters in order to make a mat with an even smaller pore size in week 5. However, the SEM was down for the entire week. Luckily it was fixed this week, and it was used today to take pictures of the nanofibrous mat. The images seen through the microscope came out much better than expected. At this time we are still waiting for the pictures to be processed and more exact information about the results obtained from the SEM will be posted as soon as they are available.

Plans for Week 5

After successfully spinning a PEO mat we are now ready for further analysis of our mats for filtration purposes. In the next few days we plan to look at the mat under an Scanning Electron Microscope(SEM) to determine the fiber size and density of the mat. Once this is determined we can speculate how successful the mat would be in filtering water toward our goals. From this information we will reanalyze the conditions of spinning and adjust the fiber density to increase the efficiency of the mat.