Replica of Leeuwenhoek microscope (Source)
Old CD-ROM drives should be readily available—perhaps from an old computer you have yet to recycle. You can also check with mom-and-pop computer shops. They may have some old non-functioning CD-ROM drives. Some shops might have old computers that never sold and are just taking up shelf space and you might be able to acquire them for next to nothing.
The only tools I needed to take apart my drive was my Leatherman Juice and Jeweler’s Philips screwdriver.
CD-ROM drive with cover and circuit board removed showing CD tray, CD spindle, and focusing lens
Closeup of CD tray, CD spindle, and focusing lens
Closeup of focusing lens
CD tray is held in the case by plastic tabs and I needed to pry the tray up away from the tabs
CD tray removed from case
There’s lots of useful bits in a CD-ROM drive including a stepper motor with a worm drive shaft, the spindle motor, a couple of neodymium magnets and, of course, the focusing lens for the laser.
Mental Note: CD tray gear meshes well with Lego Technic gear—may be useful for future a project.
You’ll need a jeweler’s Philips screw driver to remove the smaller screws.
I decided to leave the lens in its housing but cut the housing away from the focuser mechanism and had to trim away the fine copper wires.
This was my first try at creating a holder for the lens and it does leave a lot of room for improvement. The screws, nuts, washers, and rubber pulleys are Erector set parts. The plates are Steel Tec (they came with an old erector set I found at Goodwill) because the diameter of the holes are wide enough for the lens with a little wiggle room. The diameter of the holes on Erector set is too narrow.
This is a standard hardware washer and is optional. I used it to better center the lens in the hole through the plate. It also seemed to help re-center the lens housing once the nuts were tightened. As I tightened the nuts the housing moved off center, but I could re-center it by adjusting with an Erector set axle shoved between the plates.
Now to test the Leeuwenhoek microscope. I chose a slide containing a human scalp sample from my collection of slides
Operating the microscope is very simple if somewhat fiddly. Put your eye to the lens and point the lens at a light source such as the overhead lighting or lamp in your home. Bring the slide up to the lens. You’ll have to move the slide around until you find something interesting to look at. It will be fuzzy, but you can lift one side of the slide until it comes into focus.
Attempting to get a micrograph was quite fiddly. I needed something on which to rest the microscope slide so I used a jeweler’s loupe.
Then I placed the Leeuwenhoek microscope on top of the slide and placed the camera lens of my iPod on the lens of the microscope. I had to lift the microscope up slightly to bring the scalp sample into focus and then press the camera button on the iPod screen to snap the shot. This took a few tries, but I was finally able to get the following micrograph of a hair bulb and follicle:
This simplified version of the Leeuwenhoek is functional and does provide fairly decent magnification but needs much improvement. It will need a slide holder or sample holder and a mechanism to adjust the focus. I would also like to figure out a way to increase the magnification. It is, nonetheless, a simple demonstration of how to repurpose broken or obsolete technology to build simple scientific apparatus.----------
UPDATE (22 August 2014)
Fairly soon you should be able to get a Foldscope:
Foldscope is an origami-based print-and-fold optical microscope that can be assembled from a flat sheet of paper. Although it costs less than a dollar in parts, it can provide over 2,000X magnification with sub-micron resolution (800nm), weighs less than two nickels (8.8 g), is small enough to fit in a pocket (70 × 20 × 2 mm3), requires no external power, and can survive being dropped from a 3-story building or stepped on by a person. Its minimalistic, scalable design is inherently application-specific instead of general-purpose gearing towards applications in global health, field based citizen science and K12-science education.
I signed up to be a beta tester (sign up is now closed) but I don't know if I have been selected. If I am able to get a Foldscope I'll document my experience with it here on Science 2.0.