Laser Microscope: A DIY Project
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The following article was originally published in the journal for educators Biologia w Szkole (eng. Biology in School) (3/2015):
Do It Yourself
I believe the microscope holds a very important place in every biologist’s life. In fact, I would go so far as to say it occupies a special place. I say this not merely because it is such a useful tool for scientists and educators. The microscope is also a symbol of scientific curiosity about nature’s mysteries and the subsequent understanding of them. The ability to peer into the micro-world has fascinated not just scientists but also artists. In 1858, the Scottish writer Fitz James O'Brien penned the famous short story “The Diamond Lens” [1], and nearly 40 years later, the Spanish painter Joaquín Sorolla y Bastida, working in the Impressionist spirit, created “Portrait of Dr Simarro at the microscope.”
It is not easy to identify the inventor of the microscope. Some credit certain achievements to Roger Bacon [2], a 13th-century Franciscan philosopher, but this remains unconfirmed. More commonly, the first optical microscopes are said to have been built around 1590 by the Dutchmen Hans Janssen and his son, Zacharias. However, the high cost and limited capabilities of these devices prevented them from being used more widely. Another breakthrough came in the 17th century, when the merchant Antonie van Leeuwenhoek improved upon the microscope and began producing it on a broader scale. Among his accomplishments as a naturalist were his observations of red blood cells, sperm cells, muscle and bone structure, as well as bacteria and ciliates [3].
Since then, optical microscopes have been vastly refined, leading to many discoveries not only in biology but also in other fields that owe a great deal to these instruments. Microscopy itself has grown into a vast branch of knowledge. Today, apart from optical microscopes (including fluorescence, polarization, phase-contrast, confocal, and others), we also recognize electron, acoustic, and atomic-force microscopes, among others.
Not every school can afford even simple microscopes and the other equipment required to use them. Hence, I would like to present a method for building a setup to observe microorganisms at very low cost. This description may prove helpful not only to students and teachers but also to anyone enthusiastic about science.
Construction
An optical microscope consists of several basic components, including an illuminator, a condenser, a stage for the specimen, an objective, a tube, and an eyepiece [4]. But there is a simpler way!
Building a simple laser microscope does not require expensive or hard-to-obtain equipment. You only need:
- a syringe of 2–5 mL (0.07–0.17 US fl oz) capacity,
- a hypodermic needle,
- a laser diode,
- a stand with clamps,
- a screen.
The hypodermic needle’s sharp tip must be blunted by grinding it down with a metal file or sharpening stone.
The laser might seem to be the most difficult part to obtain. In reality, we’re in luck, because a laser pointer (Photo.1) is entirely sufficient for this role. However, it is not advisable to use a pointer emitting red light, as the wavelength is too long and the resulting image is not very clear. Moreover, the human eye is relatively less sensitive to red light. For these reasons, I used a green laser pointer (λ=532 nm) with a radiation output under 10 mW.
Caution: never aim laser light directly at your eyes — this can cause permanent vision damage!
A stand or laboratory clamps are helpful for securing all the parts but are not strictly necessary. Any stable way of mounting the components will do. As for the screen, you could use a projection screen, a whiteboard, a wall, or even a bedsheet.
The water containing microorganisms can be taken from a sunlit pond or from a standard culture of Paramecium caudatum or another microorganism. Water from a vase in which flowers have stood for at least a few days can also be used.
All components should be arranged according to the diagram (Fig.1).
The needle is attached to the syringe, which is filled with water containing the microorganisms.
In this microscope, the droplet of water acts as the lens. It hangs from the blunted tip of the needle and contains the microorganisms we want to observe. The laser beam directed at the droplet refracts through it, forming an image on the screen. The finished setup is also shown in Photo.2.
The droplet should measure a few millimeters (about 0.12 in) in diameter. You can adjust its size by manipulating the syringe’s plunger. System stability is crucial — if even minor vibrations occur, the droplet will fall, and you will have to form another.
Observations
The magnification depends on the droplet’s distance from the screen: the farther it is, the larger the image and the greater the magnification. However, as magnification increases, the image becomes dimmer. At a distance of around 2 m (6.56 ft), the image is fairly large (in my experiments, about 0.5–1.0 m [1.64–3.28 ft] in diameter), although darkening the room often helps in this case.
It is easy to see elongated algal cells (Photo.3A) and ciliates such as Paramecium caudatum (Photo.3B) or Stylonychia, as well as other microorganisms.
Paramecium are an excellent subject for observation because they can be very mobile. Photo.4 shows a sequence of images capturing the rapid movement (with about 0.1 s between each shot) of several of these ciliates against a background of algal cells.
Of course, the results obtained here are not ideal. Interference stripes are visible, disrupting the image. A standard school optical microscope provides better image quality. Photos.5 and 6 were taken using a simple light microscope equipped with a suitably adapted low-cost webcam. Clearly, even such straightforward solutions can provide quite good visualization of subtle details — enough for teaching biology.
Nevertheless, the extremely low cost and high educational value make this laser-based setup well suited for biology or natural science classrooms. Additionally, the resulting image is quite 'three-dimensional'. In contrast to a regular optical microscope — where observed microorganisms move only in the very limited space between a slide and coverslip (practically just two dimensions) — this setup allows you to observe their movement in three-dimensional space.
Good results can also be achieved by using a blue laser, since its shorter wavelength produces a clearer image.
References:
- [1] O’Brien J. F., Diamentowa soczewka, in: Gunn J., Droga do science-fiction, Tom 1, Signet, 1979; wyd. pol. Alfa, 1985 back
- [2] Godwin W., Lives of the necromancers: or, An account of the most eminent persons in successive ages, who have claimed for themselves, or to whom has been imputed by others, the exercise of magical power, London, F. J. Mason, 1876 back
- [3] Różniatowski T., Mała encyklopedia medycyny, Tom 2, Państwowe Wydawnictwo Naukowe, Warszawa, 1988, p. 588 back
- [4] Kurczyńska E. U., Borowska-Wykręt D., Mikroskopia świetlna w badaniach komórki roślinnej - ćwiczenia, PWN, Warszawa, 2007 back
All photographs and illustrations were created by the author.
Addendum
Static images can't fully convey the impression left by the view achieved through described method. That’s why I’ve also prepared a video, which you can watch below:
The second video presents a similar procedure using a blue-light laser pointer:
Marek Ples