Cell phone microscope

by Alfredo Mateus
Microscópio no celular

What

Print a small holder for a lens that is placed in front of the smartphone camera to take macro pictures. The lens comes from a low cost laser pointer.

Why

Observe and take pictures or video of details of things or chemical reactions are activities that can help to connect the phenomenon with the models explaining them.

How to use

Place the lens holder on your phone, so the lens is on top of the camera. Be sure to center the lens over the lens of the camera. Turn on the camera and find something that you want to look closely. The lens has a very short focal distance, so you need to place the phone very close to the object that we want to take a picture of. In my phone, the object has to around 1 cm from the lens.

instalado no celular
instalado no celular - outro ângulo

Make your own

Download the model from Thingiverse: https://www.thingiverse.com/thing:4263798

This 3D model was adapted from the holder developed by the Pacific Northwest National Laboratory (https://www.thingiverse.com/thing:667471). Their model uses a glass sphere, which has more curvature and can make the images bigger. I think that the laser pointer lens can be easier to find.

Printing the holder is very fast and uses a very small amount of plastic, so you can make several holders for your students.

After printing the holder, you will need the lens. To find the lens, simply unscrew the top of the laser pointer and remove the plastic piece inside. The lens is right below it. 

If you don't have access to a 3D printer, you can improvise a holder using a square of EVA foam with a hole for the lens. You can place it on top of the lens using adhesive tape. 

Close-up chemical reactions

Now you have a microscope, which can make video and take pictures. What are you going to point it to? We will give a few ideas of chemical reactions that can become much more interesting when you look at them really close. The cell phone has to be placed really close, so we have a very small area to focus. 

Metallic crystals

The first example, shown in the video below, is the reaction between a very small nail and a solution of copper sulfate. You can see the copper metal crystal forming as beautiful fractals. 

Next, another reaction that forms metallic crystals. A thin copper wire is covered by a silver nitrate solution. We can see silver crystals forming slowly around the wire. After 40 seconds, the video was sped up to show the results faster.

What else can we see in the microscope? Bubbles. We cut a magnesium ribbon in half lenghtway and placed a few drops of hydrochloric acid 0,5 mol/L. Changing the acid concentration can let you see what happens with the rate of the reaction. 

Finally, we have to try precipitation reactions. When we make these reactions in a test tube, the process is too fast, almost instantaneous. To observe the reaction in a "slow motion" way, we use a little trick. In a glass plate, we place one drop of each reagent separated by 1 or 2 cm. In the reaction shown in the video below, we used potassium iodide and lead nitrate. In between the two reagents, we place a drop of water, that will connect the two others. We point the camera to this middle water drop. After some time, the ions of the two reagents will find each other, as they diffuse. When they meet, beautiful yellow crystals of lead iodide appear. Since the reaction is slow, the crystals have time to grow and become bigger and shinier than those you would see in a reaction done in a test tube.

Last thoughts

Chemical reactions are not the only things your students will want to snap pictures of. Below we show a few things that they might find interesting to explore.

If you found this article interesting, leave a comment and share!

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