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.
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 are likely to lack suitably trained technicians.
That, thinks Manu Prakash, a bioengineer at Stanford University, provides an opening for a bit of lateral thinking. This led him to design a microscope made almost entirely of paper.
Foldscopes, as Dr Prakash describes them, are printed on letter-sized sheets of paper (ideally polymer-coated for durability). A pattern of perforations on the sheet marks out the microscope's components, which are colour-coded in a way intended to assist the user in 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 from bits of borosilicate or sapphire grit produced by rolling them around in tumblers that smooth-off metal parts), a light-emitting diode, a watch battery, a switch and some copper tape to complete the electrical circuit, are pressed into or bonded onto the paper. A high-resolution version 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 under ten grams, can fit in someone's pocket, requires no external power and takes standard microscope slides. Sliding and flexing the Foldscope's structure 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 or stamp on it (though not with a slide inside), and it will still work.
Making a diagnosis
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 for a particular case can affect the treatment chosen. Foldscopes should also help diagnose other widespread diseases, such as schistosomiasis, loiasis and African sleeping sickness.
He hopes, too, that they will help enthuse the next generation of doctors and scientists. His team has lined up more than 10,000 people from 130 countries to devise simple 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 apiculturalists how to identify bee-killing mites and fungi. And a 12-year-old Qatari wants 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 anyone to use.
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