The Ten Minute Leeuwen­hoek Mi­cro­scope

by Patrick Keel­ing

I was on leave from teach­ing for a cou­ple of years. The sum­mer be­fore re-start­ing my third year Pro­tis­tol­ogy course I be­gan to think about some things I wanted to change. One thing I wanted to do was to add a sec­tion on the his­tory of mi­cro­bi­ol­ogy to put things into per­spec­tive and hope­fully con­nect stu­dents with the ma­te­r­ial a bit. My col­league, Max Tay­lor, had a replica of a van Leeuw­en­hoek mi­cro­scope that he once showed to me, and I thought it would be fun to make one as close to the ori­ginal de­sign as pos­si­ble to show the class what it was like. I did some su­per­fi­cial snoop­ing around about how it was built, in­clud­ing find­ing the orig­i­nal pa­per in the Pro­ceedings of the Royal So­ci­ety where he de­scribed the de­sign. I re­al­ized it would be pretty straight­for­ward, includ­ing mak­ing a lens that was pretty close to the ones he would have used.

Patrick melts a glass tube (while look­ing away!) to make a Leeuwen­hoek micro­scope at the UBC Ad­vanced Mol­e­c­u­lar Bi­ol­ogy Labs High School Sci­ence Teacher Con­fer­ence (Oc­to­ber, 2008). Source

Deep down I knew that this was mostly to find some ex­cuse to buy an anvil be­cause, se­ri­ously, what kind of guy does NOT want to have his own anvil? So, one anvil, a big ham­mer, and a bit of brass later, I had made all the com­po­nents for two Leeuwen­hoek mi­cro­scopes. I later found a su­perbly de­tailed web page de­scrib­ing how to do it that would have saved a lot of trial and er­ror (es­pe­cially my mis­take in thread­ing both holes in the L‑shaped piece that con­nects to the micro­scope plate to the stage), a source that I would rec­om­mend to any­one who wants to make one of these.

Com­par­i­son of the same Ra­di­o­lar­ian skele­ton with two dif­fer­ent mi­cro­scopes. At left is a com­mer­cial McArthur-Cooke field mi­cro­scope set at 400X. On the right is the same skele­ton pho­tographed with the same cam­era (a Canon Elph) and at the same scale (show­ing the power of this lens to be about 200X). Source

One of the big sur­prises for me was how easy it was to make the lens with­out any grind­ing. Again, there are loads of web pages with great in­struc­tions to make one of these bi-con­vex lenses (e.g., the one linked above), and I rec­om­mend them for any­one se­ri­ous about want­ing to repli­cate one of these mi­cro­scopes. But it also got me to think­ing: my idea of show­ing a replica mi­cro­scope to my class would be al­right, but it would be way bet­ter still to have them ac­tu­ally make and use one them­selves. The lens is the in­tim­i­dat­ing part, but that was easy, so what about the rest of the mi­cro­scope?

It is im­me­di­ately ob­vi­ous that the plates that sand­wich the lens can be made of stiff pa­per, but de­vis­ing a me­chanism to hold the sam­ple and fo­cus it was harder. I tried a few so­lu­tions that were overly com­plex, not to men­tion fail­ures, but then had an idea to use sticky tack. This is the gummy stuff used to hold posters up on the wall. It is not only sticky, but also has great elas­tic prop­er­ties, so you can use it to mount all kinds of sam­ples in front of the lens and also to pivot the sam­ple away from or to­wards the lens. This, in a stroke, elim­i­nates the two biggest de­sign prob­lems with a pa­per mi­croscope, and I think that if Leeuwen­hoek had sticky tack in the sev­en­teenth cen­tury, he would have used it, too.

Ex­am­ple of an im­age with a lower mag­ni­fi­ca­tion lens of live cells in liq­uid on a cover glass. This is the hy­per-mastig­ote parabasalian Tri­cho­nympha from the hind­gut of the ter­mite Zooter­mop­sis an­gusticolis. Source

In any case, I made a few of these and they all worked well and were easy to put to­gether, so I set up the first three labs in my class to tie into lec­tures about the his­tory of mi­cro­bi­ol­ogy and tax­on­omy. The stu­dents made their own mi­cro­scopes, mea­sured the size of their lenses, and cal­cu­lated the power, thus learn­ing some­thing about op­tics. They then used them to ob­serve nat­ural sam­ples. Af­ter that, they ob­served the same sam­ples with the 1960s tech­nol­ogy at their dis­posal in the lab, so they ex­pe­ri­enced how it felt for the pi­o­neers of mi­cro­bi­ol­ogy.
 

All of the stu­dents made de­cent mi­cro­scopes. In­deed, this class has a lab exam at the end of the first term, and for one of the 'sta­tions' dur­ing the exam they were not given a mi­cro­scope. In­stead, they had a fixed slide, a Pas­teur pipette, some pa­per, and a Bun­sen burner. They were given 10 min­utes to make a mi­cro­scope that was good enough to iden­tify the pro­tists on the slide. Hap­pily, the stu­dents aced this ques­tion, so tech­ni­cally this project is pretty ac­ces­si­ble.

It also seemed pretty pop­u­lar with the stu­dents. A lit­tle while later I was asked to demon­strate the lab to some pub­lic school teach­ers at a pro­fes­sional de­vel­op­ment day or­ga­nized by David Ng and Joanne Fox at UBC (who posted a cou­ple movies from the day on YouTube). My­self and the TA from my class, Gillian Gile, taught 90 teach­ers how to make one, and again it seemed pretty po­pular. Some teach­ers have al­ready used the ex­er­cise in their class, and a cou­ple re­ported back that it worked well with stu­dents of a broad range of ages. One teacher even told me that she was go­ing to in­clude pro­tis­tol­ogy in her cur­ricu­lum in the fu­ture so the lab had bet­ter con­text, which I thought was great. I have also had a cou­ple stu­dents demon­strate this di­rectly to pub­lic school stu­dents and re­port back that it was pop­u­lar and suc­cess­ful.

Over­all, this has been a great ex­pe­ri­ence. I find that get­ting peo­ple in­ter­ested in mi­cro­bi­ol­ogy and mi­cro­scopes is chal­leng­ing, I think be­cause the mi­cro­bial world is so ab­stract to them. By delv­ing into the his­tory, the stu­dents ex­pe­ri­enced a fas­ci­na­tion akin to that felt by many young stu­dents in physics when en­coun­ter­ing the his­tory of its pi­o­neers. But be­ing able to build a six­teenth cen­tury mi­cro­scope your­self is bet­ter still (and al­though you don't need an anvil, you still get to play with fire and use a drill, so it is a lot of fun!). I would rec­om­mend try­ing this with any class or lab from high school up to se­nior un­der­grads, and if you do please let me know how it goes, or if you can sug­gest any im­prove­ments.

I made a set of in­struc­tions and posted them on my web page, so any­one should be able to quickly make one of these, and teach their class how to do it too.

Patrick Keel­ing is a scholar of the Cana­dian In­sti­tute for Ad­vanced Re­search, Evo­lu­tion­ary Bi­ol­ogy Pro­gram, and as­sis­tant pro­fes­sor, De­part­ment of Botany, Uni­ver­sity of British Co­lum­bia.