The Effect of Cleaning Methods on the Approximate Bacterial Count of a Cell Phone Case

Table: 11
Experimentation location: School
Regulated Research (Form 1c): No
Project continuation (Form 7): No

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Works Cited

CDC. “Frequent Questions About Hand Hygiene | Handwashing.” CDC, Accessed 28 January 2022.
Higuera, Valencia, and Tim Jewell. “The 9 Dirtiest Places in Your Home: Find Out Where the Germs Live.” Healthline, Accessed 28 January 2022.

Additional Project Information

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Research paper:
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Project files

Research Plan:


Cell phone cases are incredibly dirty. They often have large amounts of bacteria, mold, yeast, and even fecal matter festering on their surfaces. However, most people rarely clean their devices. This experiment tested if changing the way you clean a phone case will affect how much bacteria can be found on it.

Research Question:

Which cleaning method limits the bacterial count on a cell phone case the most?


  1. Lay the cell phone case next to the ruler. Using the ruler, put strings or markings every two inches or so as to divide the case into four areas
  2. Using one swab at a time, slowly rub the swab in a motion like striking a match along the back of the cell phone. Take two samples from area 3. After each individual swab has completed this motion, rub the swab in a zigzag motion along the surface of the liquid in an Agar plate for thirty seconds or follow the manufacturer’s instructions (Use one dish per swab). Use separate dishes for each and label the dishes. Discard swabs after use. 
  3. Next, take the wet wipe and clean area 2 of the case. Take two samples of this cleaned area and put them on Agar plates using the same method as before, making sure to label them. Dry the phone case.
  4. Take soap and water and wash off the top area of the case (area 1) with soap and water. Hold the case upside down so the water does not clean the rest of the case. Take another two samples of bacteria plates from area 1 and label them.
  5. Pour 120 ml of isopropyl alcohol into a beaker. Put the phone case into the alcohol, making sure the bottom area (4) is covered, and leave it there for five minutes (time with the stopwatch). Take the case out and take the final two samples from area 4. Label them as well.

  6. After this is done, put the lids on the plates (leave them slightly ajar). Then, place the plates into the tray (keep them flat) and turn on the lamp (make sure it is pointing at the samples). Give the bacteria exactly three days to grow. 

  7. At the end of the waiting period, remove the samples from the box. Count the colonies of bacteria on the samples. Take pictures and record data.

  8.  Spray all bacteria with isopropyl alcohol. Put the agar plates in a Ziplock and seal. Dispose of all bacteria in trash. DO NOT KEEP ANY BACTERIA OR PLATES.

Risk and Safety:

This experiment uses bacteria samples grown on Agar plates. These samples will be handled with gloves. After the experiment, the samples will be sprayed with isopropyl alcohol, put in a labeled and sealed plastic bag, and thrown out.

Questions and Answers

1. What was the major objective of your project and what was your plan to achieve it? 

The main objective of my project was to discover the effect different cleaning method have on the approximate bacterial count of a cell phone case. My plan was to take samples from a cell phone case that had different areas cleaned in different ways and grow said samples on Agar plates.

       a. Was that goal the result of any specific situation, experience, or problem you encountered?  

This goal was a result of a sign I saw that stated that the average phone has more germs than the average toilet. I thought about how fast germs were spreading during the pandemic and wondered if there was a way to find out the best cleaning methods.

       b. Were you trying to solve a problem, answer a question, or test a hypothesis?

I was trying to solve a problem.

2. What were the major tasks you had to perform in order to complete your project?

I had to clean the parts of the phone, collect the samples, set up the incubator, leave the samples in the incubator for 72 hours, and count and dispose of the bacteria samples.

       a. For teams, describe what each member worked on.


3. What is new or novel about your project?

       a. Is there some aspect of your project's objective, or how you achieved it that you haven't done before?
I have never grown bacteria samples before, so I thought that was an interesting experience.

       b. Is your project's objective, or the way you implemented it, different from anything you have seen?

I have never done such an in-depth science project before, so this was a little new to me.

       c. If you believe your work to be unique in some way, what research have you done to confirm that it is?

4. What was the most challenging part of completing your project?

The most challenging part of my project was thinking of a way to count the bacteria. In the end, I decided to estimate the amount.

      a. What problems did you encounter, and how did you overcome them?

I realized that I needed build a proper incubator. In the end, I used an aluminum tray and a desk lamp.

      b. What did you learn from overcoming these problems?

I learned that you can always find simple solutions to challenging problems.

5. If you were going to do this project again, are there any things you would you do differently the next time?

In the future, I think that I would divide the phone from top to bottom. Having vertical strips instead of horizontal areas would likely ensure that the slides all have similar amounts of bacteria on them. I would also add more tests to ensure more data is collected, and I would also find a better way to count the colonies of bacteria.

6. Did working on this project give you any ideas for other projects? 

I would like to test the bacterial count and cleaning methods on other household items as well.

7. How did COVID-19 affect the completion of your project?

COVID actually inspired my project. I completed it in my school's laboratory, so COVID didn't really affect my project at all.