Build Simple Smartphone Microscope With A Ball Lens


This is not a brand-new idea.  In an October 6, 2011 article of Laser Focus World, it was reported that “UC Davis researchers prove that iPhone plus ball lens equals useful microscope”.  Their work stimulated a lot of people to turn their smartphones into microscopes and explore the fascinating micro world.  Not only the amateurs are amazed by the simplicity of the iPhone microscope, many serious scientists are also working on to make this tool more practical and user-friendly, so people can use it to solve real-world problems.  Pacific Northwest National Laboratory posted on their website an article “PNNL Smartphone Microscope” to introduce their work, and even provided DIY instructions and 3D-printer files for needed accessories.   

In this article, we will first give detailed instructions on the simple process of building an iPhone microscope with a ball lens, and then show some pictures we took with our own iPhone.  We encourage everybody with curious mind to try this project.  It is simple.  However, the window it opens is astonishing. The ball lens used in this project can be ordered with only a few dollars. Different size ball lens will give different magnification.

Materials: smartphone, 1mm diameter ball lens, ~1mm thick cardboard, microscope cover glass, thin double-sided tape, flashlight

The cover glass is a very thin piece of glass widely used with traditional microscope, as shown below:

Cover Glass


Step 1.

Cut a piece of square cardboard (for example, 10mm x 10mm, or any other similar size), and punch a hole about 1 mm diameter at the center.

Cardboard and Ball Lens

Step 2.

Push the 1 mm ball lens into the hole of the square cardboard.

Step 3.

Add a small piece of double-sided tape onto one side of the cardboard so later the cardboard can be secured on the smartphone. Make sure the tape is away from the ball lens so it won’t interfere with the optics.

Step 4.

Put the smartphone on the table, turn on the front-facing camera (the selfie camera).  Either the front-facing camera or the rear-facing camera can be used.  Here we choose the front-facing one for simplicity.

Step 5.

Put the cardboard with the ball lens on the smartphone, with the double-sided tape between the cardboard and the smartphone.  Move the cardboard so the ball lens is centered with the smartphone camera.  When the ball lens is aligned well with the camera, you will see a round area with its center at the center of the screen.  Then you can press the cardboard so the double-sided tape can secure the cardboard on the smartphone.

Ball Lens and Camera Alignment

Step 6.

Put the microscope cover glass on the cardboard.  Now your smartphone microscope is built.  you can put your sample on the cover glass and you should see the image of a micro world.  You can use a flashlight to illuminate your sample from different angle to enhance the contrast of the image.  The angle chosen is dependent on the sample.  If it is a reflective sample, you can illuminate from one side, and if it is a transmissive sample, you can illuminate from top.  Sometimes you need to try different angles to get a better image.

Alignment and Illumination

Here we show  several pictures we took with our own iPhone microscope.

The first one is the compound eyes of a fruit fly.  A flashlight was used to illuminate from the side.

Compound Eyes of Fruit Fly

The second one is the leg of an ant. A flashlight was used to illuminate from the top.

Leg of an Ant

The third one is the skin cell of an onion. A flashlight was used to illuminate from the top.

Skin Cell of Onion

As mentioned earlier, we encourage people to put their hands on this project, build their own simple ball lens microscope.  

So, roll up your sleeves, and have some fun!

p.s. You can use a different size (e.g. 1.5mm, 2.0mm, 2.5mm, 3.0mm diameter) ball lens instead of the 1 mm diameter one.  It’s easier to handle with larger size, with the trade-off of some magnification power decrease (from ~×350 down to ~×100).