IF EVER a technology were ripe for disruption, it is the microscope. Benchtop microscopes have remained essentially unchanged since the 19th century—their shape a cartoonist’s cliché of science akin to alchemical glassware and Bunsen burners. And that lack of change has costs. Microscopes are expensive (several hundred dollars for a reasonable one) and need to be serviced and maintained. Unfortunately, one important use of them is in poor-world laboratories and clinics, for identifying pathogens, and such places often have small budgets and lack suitably trained technicians. That, thinks Manu Prakash, a bioengineer at Stanford University, provides an opening for a bit of lateral thinking. And Dr Prakash’s mental sideways movement has led him to design a microscope made almost entirely of paper, which is so cheap that the question of servicing it goes out of the window.

Individual Foldscopes, as Dr Prakash dubs them, are printed on A4 sheets of paper (ideally polymer-coated for durability). A pattern of perforations on the sheet marks out the ’scope’s components, which are colour-coded in a way intended to assist the user in the task of assembly—for the Foldscope has no written instructions to guide, or possibly frustrate, the user.

The Foldscope’s non-paper components, a poppy-seed-sized spherical lens made of borosilicate or corundum, a light-emitting diode (LED), a watch battery, a switch and some copper tape to complete the electrical circuit, are pressed into or bonded onto the paper. (The lenses are actually bits of abrasive grit intended to roll around in tumblers that smooth-off metal parts.) A high-resolution version of this costs less than a dollar, and offers a magnification of up to 2,100 times and a resolving power of less than a micron. A lower-spec version (up to 400x magnification) costs less than 60 cents.

The whole device weighs less than 10 grams, can fit in someone’s pocket, requires no external power and takes standard microscope slides. Sliding and flexing the Foldscope’s struts with thumb and fingers (see picture) lets the user move a slide around and then focus on the relevant bit of it. The Foldscope can be adapted, by fitting it with a more powerful LED, to project what it sees onto a screen, and the design can be modified to accommodate multiple lenses or filters. Dunk it in water, drop it from a rooftop or stamp on it (though not with a slide inside), and it will still work.

Dr Prakash sees the Foldscope’s main use as a diagnostic tool for tropical diseases. Malaria, for example, can be caused by several species of parasite. Knowing which is responsible in a particular case can affect the treatment chosen. Foldscopes should also help diagnose other widespread diseases, such as schistosomiasis, loiasis and sleeping sickness.

He hopes, too, that they will help enthuse the next generation of doctors and scientists. To this end he and his team have drummed up more than 10,000 people from 130 countries to devise simple, relevant microscopy-based experiments. A Mongolian farmer, for instance, wants to show his fellows why they should boil milk to make it safer. An American beekeeper proposes to use Foldscopes to show his fellow apiculturalists how to identify bee-killing mites and fungi. And a 12-year-old Qatari would like to study the Namib desert beetle, which scavenges drinking water from morning fogs. The results, when published on the web, will become part of a manual of microscopy for everyman (and woman) that Dr Prakash hopes will encourage yet more experimentation.