A disposable microscope for as little as $1

A Foldscope demonstration in a lab in Bengaluru, India.  

Manu Prakash, an assistant professor of bioengineering at Stanford University, and two of his students have re-imagined the microscope to come up with a nifty device that’s printed on paper and folded like origami.

Dubbed the ‘Foldscope’, this invention is cheap — costing less than $1 apiece — rugged, very easy to use, and versatile enough to screen for a variety of diseases on the field, including malaria, chagas, giradia and leishmaniosis.

Microscopes are optical tools whose conception in the early 1800s marked the birth of humankind’s fight against disease-causing micro-organisms, which today plague the world’s tropics and leave over a billion at risk of getting infected annually. However, the standard-issue optical microscope currently in use is bulky, costly, and far too sophisticated to be used by just about anyone.

Through >a TED talk uploaded last week, Prakash — a graduate of IIT-Kanpur and the Massachusetts Institute of Technology — demonstrated how the Foldscope could prove a remarkable alternative for doctors in the field as well as school students experimenting with optics.

Its mechanical parts are printed on cardstock paper. The sample to be studied, mounted on a glass slide, is slid under a plastic fixture holding the ball lens. The fixture in turn is attached to a strap of paper that passes under buckles on either side of the slide. To pan in two dimensions, the slide can be pushed in or out further and the strap can be moved left or right under the buckles.

To focus, a third depth movement is achieved by pulling or pushing against the strap, where mechanical tension causes the strap to flex upward or downward. A vernier scale is marked around the buckles for better coordinated movement and precision.

Together, the paper-parts comprise the illumination and sample-mounting components. The optical components include a spherical ball-lens of radius 40-1,200 micrometres, fixtures, LED and a battery. To ready the Foldscope, punch out the parts, piece them together with the help of how they’re colour-coded, and fold along the marked lines. That's it.

The folding plays an important structural role. To quote from >their paper submitted to arXiv on March 5: the “folding features form a closed structural loop between the optics stage and the illumination stage. This improves alignment repeatability.”

The Foldscope alters only the shape and size of the microscope. The sample to be studied is still mounted as a stain on a glass slide, which has become an industry standard. It is extremely space-efficient, too. The total optical path length from the light source to the last lens surface is about 2.7 mm, while that of a conventional microscope is around 300 mm. The great magnification is achieved by exploiting the fact that magnification is inversely proportional to the ball-lens diameter.

The total cost varies according to the magnification to be achieved. An apparatus that enables a 2,000x magnification, sufficient to spot organisms like Leishmania donovani, malarial parasites and E. coli, costs a meagre $0.97 and weighs about 8 grams.

Prakash said their team will start field-trials by the end of December, 2014, after which they will be in a position to print thousands of Foldscopes. His work was carried out with grants from various institutions, including one from the Bill & Melinda Gates Foundation in 2012.

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Printable version | Apr 10, 2021 10:26:50 PM |

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