Picture This: Building a Cell Phone Microscope
AbstractImagine you are on a trip and see something interesting that you want to share with your friends. What do you do? You take a picture with your cell phone and e-mail it to them, of course. But did you realize that the same technology can be used to save lives? Using their cell phones modified as inexpensive microscopes, medical personnel can look at blood smears to help diagnose diseases like malaria and cholera. In this photography science project you will build a simple and inexpensive cell phone microscope and use it in your choice of imaging applications.
Michelle Maranowski, PhD, Science Buddies
- RadioShack® is a registered trademark of RadioShack Corporation.
This project is based on the following article: Mosher, D. (2011, March 11). Turn your cellphone into a high-powered scientific microscope. Wired Science. Retrieved May 7, 2012, from http://www.wired.com/wiredscience/2011/03/diy-cellphone-microscope/
To build a cell phone microscope and use it in an imaging application.
When you get sick, you generally go to your doctor, get a prescription for what ails you, and feel better soon thereafter. But in parts of the world that are remote, people cannot visit doctors as easily. A doctor or nurse may not live close by. Even if a person could visit the doctor, he or she may not have the facilities or tools, like microscopes, to quickly diagnose and start treating that person's diseases. Doctors need microscopes to diagnose accurately such diseases as malaria and cholera, both deadly when left untreated.
Although not everyone on earth has ready access to health-care providers, 80% of the world has cell-phone coverage. So is there a way to use cell phones to give people living in non-urban areas access to health and testing facilities? Yes—cell phone microscopes! Many of us take pictures with our cell phone cameras. With a few extra parts, that same camera can easily be converted into a microscope. A microscope is used to magnify a specimen, so that you can examine features that you would normally not be able to see with the unaided eye. The cool thing about cell phone microscopes is that you can take a picture of the specimen, save it, and share it with others. Researchers have developed both hardware and software methods for using cell phones in microscopes. In this science project, we will focus on a hardware approach to building a cell phone microscope. First, watch this video describing a cell phone microscope.
How does a microscope that you see in your school's science lab work? The microscope at your school is probably a compound microscope like that in Figure 1. A compound microscope is made up of two lenses that serve to magnify the specimen: an objective lens and an ocular lens. Both lenses are convex lenses. The objective lens mainly determines the level of magnification. A light source illuminates the specimen from below. The light rays from the specimen then pass through the objective lens. The objective lens causes the light rays to bend and focus on a point referred to as the focal point of the lens, forming an enlarged image. The distance between the lens and the focal point is the focal length. For the microscope to magnify, the specimen needs to be placed just outside of the focal length of the lens. The more the objective lens bends the light, the shorter the focal length, and the higher the magnification. The light rays then travel from the image made by the objective lens to the ocular, or the eyepiece, lens, which if placed correctly further magnifies the image. The ocular lens often magnifies by ten times. Figure 2 shows how a convex lens bends light rays to form images. In this example, the object or specimen is outside the focal point and the resulting image is inverted on the other side of the lens.
The two lenses that are used to enhance the viewing of specimens are the ocular lense and objective lense. The objective lense determines the level of magnification. The light source at the bottom shows light through the speciment stage and is shown to the objective lense.
Figure 1. Compound microscope with its major components labeled.
Figure 2. Diagram of how a convex lens bends light rays. In this example, the object (or specimen) is outside of the focal point (denoted by the letter "f") and results in a real and inverted image on the other side of the lens.
In this photography science project, you will build a cell phone microscope with a 1 millimeter (mm) glass ball lens and then use it in an imaging application of your choice. The 1 mm glass ball acts as the objective lens in the cell phone microscope. It is tricky to handle but provides a high magnification. Included in this science project are step-by-step instructions on how to build a cell phone microscope. Although building the cell phone microscope is fun, it will not provide a sufficient level of effort to compete well at a science or engineering fair, and you will need to apply your cell phone microscope to some problem or question. The end of the Experimental Procedure includes a list of applications you could tackle with your cell phone microscope. You can also develop your own tasks for the microscope you make.
Terms and Concepts
- Compound microscope
- Objective lens
- Ocular lens
- Focal point
- Focal length
- How does a compound microscope work?
- Does the radius of the glass ball or objective lens affect the magnification of the image?
- How is the focal length related to magnification?
- How does a cell phone camera function? How does it store information? Is it similar to or different from a digital camera?
- Sherwood, C. (2010, July 15). New in telemedicine: The cell phone microscope. Smartplanet. Retrieved May 7, 2012.
- Rodewald, M. (2010, June 29). UCLA engineer's telemedicine invention poised to begin trials in Africa. UCLA Newsroom. Retrieved May 7, 2012.
- SmartPlanetCBS. (2010, July 7). Turning a cell phone into a microscope. Retrieved May 7, 2012.
- Rayment, W. J. (2012). How a compound light microscope works. InDepthInfo on the Microscope. Retrieved May 7, 2012.
Materials and Equipment
Materials are only for making the cell phone microscope. Depending on what you choose to investigate with the microscope, you may need additional materials.
- Bicycle inner tube, 1 mm thick. You can purchase an inner tube and cut a 3 x 3 centimeter (cm) piece to use from it. A bicycle inner tube is available online from Amazon.com.
- Disposable gloves (1 pair)
- Paper towel
- Ball lens, 1 mm in diameter (2). You can purchase a ball lens online from Edmund Optics. Although the project only requires one lens, the ball lens is hard to handle and can get lost easily. Buy a second lens as a backup.
- Tweezers for handling the ball lens. Various tweezers are available from Jameco Electronics.
- Cell phone with built-in camera. The cell phone that you use should at least be able to zoom in and out manually and focus.
- Optional: Volunteer
- Electrical tape
- Toilet paper tubes (2)
- Screwdriver, Phillips-head
- Mini incandescent bulb, available from Jameco Electronics
- AA batteries (8), available from Jameco Electronics
- 8xAA battery holder, available from Jameco Electronics
- Alligator clip cables (2), available from Jameco Electronics
- Prepared microscope slide specimen. (Ask if you can borrow a slide from your school's science lab for testing your cell phone microscope.)
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Building the Cell Phone Microscope
In this project you will build a cell phone microscope using a glass ball lens, a small square of thin rubber, and electrical tape. You will use the small piece of rubber to hold the ball lens and then tape the rubber-and-lens assembly to the cell phone camera lens.
- If you are using a bicycle inner tube for the rubber square, for a better grip and to avoid getting rubber lubricant on your hands, put on your disposable gloves before cutting it. The rubber will be used to hold the ball lens in place.
- Cut a section from the inner tube that is 3 cm wide.
- Many bicycle inner tubes have lubricant inside, and it can get a little messy cutting them open. Make sure to wear gloves while cutting the tube.
- Dispose of the inner tube as soon as you finish cutting off a section.
- Clean up any excess lubricant that may have dripped from the inner tube.
- Thoroughly wash the section of rubber with water, making sure that you remove all of the lubricant from it. Dry it completely with a paper towel. Wash the scissors and make sure that they are free of lubricant.
- Dispose of the gloves and then cut the rubber into four pieces for easier handling later on.
- Make a hole in one of the pieces of rubber with the pushpin. The hole should be large enough to accommodate the ball lens, but not so big that the ball lens falls through.
- Insert the pushpin into the center of the rubber piece to make the hole.
- Insert the pushpin several times into the same hole, twist the pushpin around as if it were a screw, and stretch the rubber to enlarge the hole.
- The hole should be clean and without rough edges.
- Insert the ball lens into the hole in the rubber piece.
- Inserting the ball into the hole will take time and lots of patience, so do not give up.
- Use the tweezers to handle the ball lens carefully. Your volunteer can help by holding and stretching the rubber as you insert the lens.
- Try to avoid handling the ball lens with your bare fingers. Your skin has oils that can stick to the ball lens and affect image quality.
- Once the ball lens is firmly inserted into the rubber, cut the rubber into a small round "iris" (similar to that on a human eye, with the ball lens as the pupil) that is just a little bit larger than the cell phone's camera lens. Avoid touching the lens with your bare hands.
- Position the iris centrally on top of the cell phone's camera lens, as shown in Figure 3.
- Use pieces of electrical tape to hold the iris in place. You can see how the electrical tape in the figure is placed going around the edge of the phone.
- Tape the iris down by the edges, making sure to not cover the ball lens in the middle.
Figure 3. Pieces of electrical tape hold the iris over the cell phone's camera lens. This makes a complete cell phone microscope.
Assembling the Cell Phone Microscope Stand
Now you will build a stand from two paper tubes. One tube will hold and illuminate the specimen and the other tube will hold the cell phone microscope.
- Create a stand to light and hold a microscope slide. The stand will enable you to keep the cell phone microscope as still as possible while testing it. Stillness and plenty of light are needed in order to maximize image quality.
- Use scissors to make two notches directly across from each other on the side and bottom of the paper tube, as shown in Figure 4.
Figure 4. Paper tube with notches across from each other. The notches should be deep enough to accommodate wires.
- Connect one end of the red and black alligator clip cables to the two leads of the mini incandescent bulb, as shown in Figure 5.
Figure 5. Red and black alligator clips connected to the bulb.
- Insert the eight AA batteries into the 8xAA battery holder. Make sure the "+" signs on the batteries line up with the "+" signs on the battery holder.
- Connect the other ends of the alligator clip cables to the red and black leads from the battery pack. This completes the circuit and your bulb should light up.
- Set the paper tube over the bulb so that the cables come through the notches, as shown in Figure 6.
Figure 6. The paper tube sits easily over the bulb, with the cables from both sides passing through the notches.
- Place the prepared microscope slide specimen on top of the paper tube so that the light is shining through it. Figure 7 shows a light in a paper tube shining through a slide.
Figure 7. The partially complete microscope stand. The incandescent bulb is connected to the battery holder with alligator clip cables, and a paper tube with notches cut in the bottom is placed over the bulb.
- To create a tube to hold the microscope cell phone steady, attach the middle of the cell phone, with the camera lens facing down, to a second paper tube with electrical tape. Make sure that the tube doesn't cover up or come within several centimeters of the iris. The paper tube supports the cell phone microscope and enables you to zoom and focus on the sample with ease. Figure 8 shows a cell phone microscope attached to a paper tube with electrical tape.
- The cell phone microscope and stand is now complete and ready for testing.
Figure 8. The cell phone microscope is mounted on a paper tube, which steadies the microscope and makes zooming and focusing on the specimen easier.
Testing the Cell Phone Microscope
- Turn on the cell phone microscope by activating the cell phone's camera function and place the iris of the cell phone microscope directly over the lighted specimen on the microscope stand. You will have to experiment with the cell phone camera's zoom and focus to get a clear image.
- You will have to determine how far away the slide must be from the lamp to best illuminate the specimen. Cut off the top of the paper tube on the microscope stand in even strips as needed, a little at a time to avoid cutting off too much. You may have to adjust the height of the paper tube attached to the cell phone microscope as well.
- Once you get a clear image, take the picture. What is your estimate of the magnification of the image?
Using the Cell Phone Microscope in Different Applications
- Scientists, engineers, and researchers use microscopes to get more information about the specimens they study. You, too, can use the cell phone microscope to study different things. Following is a list of projects that you can develop and study further with the cell phone microscope you built.
- Investigate the silt deposits in different regions of a stream using your cell phone microscope. This abbreviated project idea will give you more information: Silt Deposits in Streams.
- Use your cell phone microscope to get a close-up view of the particles in the air you breathe in this Science Buddies science project: Air Particles and Air Quality.
- You can use microscopes to measure the dimensions of small objects like yeast or daphnia. See this Rice University webpage to learn more about ocular micrometers and to come up with a procedure to use the cell phone microscope as a micrometer.
- Prepare your own microscope specimen slides. Read this Home Science Tools Introductory Microscope Experiments for a discussion of how to make microscope slides and possible specimens to look at.
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