Sunday, September 13, 2015

Mini Microscopes

Last year, I became curious about the options for cheap, but good microscopes. I expected to find some decent equipment available for approximately $100, with more powerful equipment available at higher price ranges.

To my surprise, the options are better and cheaper than I expected.

The $2.50 Microscope. Cell phone not included.
First, I discovered that moderate-power microscopes that attach to a cell phone (and make use of its built-in camera) are remarkably cheap. At the time of writing, a quick search of Amazon indicates that the cost of a 60x microscope that attaches to a cell phone is about $2.50. These little gizmos are extremely portable, project via the cell phone display to allow multiple people to view at the same time, and are just good enough to resolve large plant cells. This was an amazing find for the money, and allows a lot of fun, educational experiences for little effort.

To my even greater surprise, I later found out that significantly more powerful magnification can be produced for even cheaper.

The Foldscope project, run by Manu Prakash at Stanford University, strives to make powerful (and durable) microscopes available at ultra-low prices for clinical and educational use around the world. The premise is this: A microscope with incredible resolution (sufficient for viewing bacteria, and approaching the absolute limit that is possible for an optical microscope) can be assembled in minutes from parts costing under $1! Moreover, the resulting device is ridiculously portable and resistant to damage, able to survive abuse that would pulverize a typical microscope. (And, if you do manage to destroy it, so what? Build another one from scratch for under $1.)

How is this possible? Obviously, the answer is simplicity. While a conventional microscope has a pair of lenses built into an optical path with precision engineering, a Foldscope has only one lens and the user controls the focus by manually adjusting the position of the Foldscope and its parts from the eye.

The 40¢ Microscope
There is one other catch: The recipe for making a Foldscope is not completely fleshed out. Currently, there is a beta test in progress. Instructions for assembling a Foldscope have been published, but these instructions are not quite ready for prime time. And so, last spring, I resolved to wait until Prakash’s group had produced a “final” set of Foldscope instructions.

But I was only willing to wait so long. In October, I downloaded some slightly-contradictory sets of instructions, ordered the parts online, and sat down to make myself a Foldscope. At first, I spent over an hour carefully trimming parts out of a printout (carefully-folded paper is the main structural component of a Foldscope, hence the name). Then I needed to mount a lens, which was not very well described in any of the materials before me. So I improvised, sandwiching a 2.4mm borosilicate sphere (the lens) between two small pieces of printer paper, held tight using Elmer’s Glue.

Paramecium Photographed with the 40¢ Microscope
And lo, it worked. Without even using the rest of the Foldscope that I had so carefully sliced out a printout, this tiny, postage-stamp-sized microscope worked. Here’s the tale of the tape: 140x magnification for 40¢. All I had to do was press it against a prepared slide (stained onion epidermis was my first test item), hold it close to my eye, look up at a light and fiddle around with the distances between my eye, the lens, and the sample. Within seconds, I found a good focus and could clearly see the cell nuclei. A few minutes later, I was clearly seeing human blood cells, and by holding the whole setup against my cell phone camera, I was taking pictures of these samples. Amazing!

One remarkable thing about mini microscopes is this: Hardly anybody realizes that they exist, or even that they can exist. I've shown them to medical doctors, a microbiologist, the coordinator of science at a private school, and many other well-educated adults working in technical fields; they were all astonished that such a thing is possible. Maybe one day, people will carry a microscope everywhere they go. This could happen today. For various reasons, the use cases and usability have not come together to start a revolution in widespread microscope use. Maybe that will change someday soon.