Forget the new iPad - the sub-10-cent oPAD could save lives


March 9, 2012

The simple, inexpensive, folded-paper-based oPAD could detect diseases in body fluid samples

The simple, inexpensive, folded-paper-based oPAD could detect diseases in body fluid samples

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In First World countries' medical systems, the standard way of checking a patient's body fluid samples is to send them off to a lab. In developing nations, however, such labs often don't exist, nor does the infrastructure for transporting biological samples. Fortunately, a number of groups have been developing simple, inexpensive testing devices that could be used by clinicians in these countries. One of the latest gadgets is the very simple origami Paper Analytical Device, or oPAD - it's made out of paper, could be purchased for under 10 cents, and is folded together by the user.

The device was invented by Hong Liu and Richard Crooks, chemists at the University of Texas at Austin. Liu got the idea after reading a paper by Harvard chemist George Whitesides, who had created a three-dimensional microfluidic paper-bodied biosensor. Whitesides' device, however, required multiple pieces of paper to be patterned using photolithography, cut with lasers, then stuck together with two-sided tape. This somewhat complex production process would presumably be reflected in its price, and would require that it be assembled by trained personnel.

Liu remembered being taught origami as a child in China, and wondered if a similar sensor could be created from a single sheet of paper, shipped flat, then folded into shape on-site. After a few weeks of experiments, he discovered that it indeed could.

Sheets of paper being run off for use in oPADs, on an office printer

The principle is relatively straightforward. Using photolithography or even an office printer, a hydrophobic material such as wax or photoresist is deposited into miniature canyons on chromatography paper. When a liquid sample is introduced, those canyons guide it to areas on the paper treated with reagents. Should the sample contain the targeted substance, then the reagent will visibly react by changing color, or fluorescing under ultraviolet light. Different reagents can be used, depending on what's being tested for.

Many people, of course, are already familiar with paper sensors such as those used for pregnancy tests. The oPAD, however, is able to test for more substances using a smaller surface area, and is able to perform more involved tests.

In its current form, the paper must be unfolded at the end of the process, to reveal the color of the reagent. The scientists, however, have already developed a method of equipping the oPAD with a small battery, that could do things such as lighting up a small bulb if a given substance was present. They estimate that it would only add a few cents to the cost of the device.

A paper on the research was published last week in the journal Analytical Chemistry.

Source: University of Texas at Austin

About the Author
Ben Coxworth An experienced freelance writer, videographer and television producer, Ben's interest in all forms of innovation is particularly fanatical when it comes to human-powered transportation, film-making gear, environmentally-friendly technologies and anything that's designed to go underwater. He lives in Edmonton, Alberta, where he spends a lot of time going over the handlebars of his mountain bike, hanging out in off-leash parks, and wishing the Pacific Ocean wasn't so far away. All articles by Ben Coxworth

Great but there is no reason that they can't be used in the first world as well.


@ Slowburn - My thoughts exactly. I keep reading about these lab-on-a-chip type devices, which always seem targeted at Africa and what-not, we need them here (in the US) to get these crazy healthcare costs back down to a more sane level.

Derek Howe

@Slowburn and Derek: I think the tests here in the "developed" parts of the world are of a much higher thoroughness, certainty and quality than paper tests will ever be. In parts of the world where high quality tests are available, those will always be preferred. Where they're not, paper tests are much better than nothing at all.

Joris van den Heuvel

re; Derek Howe

The real cause of the spiraling cost of health care is that nobody actually pays for it themselves so there is no push for lower prices. However things such as LASIC which insurance does not cover the price has come down.


Home pregnancy test is a good example. Used to have to kill a rabbit and it took days, also expensive. New home tests would go a long way towards screening at home, then confirm and treat at the doctors office. A lot of time and expense is taken up with seeing healthy people in a sick environment. Make screening tests available OTC and cheap enough to actually use and stay away from the doctors offices until you need to. Saves the doctors time for what they are trained for instead of "hand holding". Or eat an apple a day ;).


All good ideas literally on paper! And some have been patented by Whitesides groups at Harvard and are currently being sold for about $0.05 in India as liver function tests via 2 enzymes, AST and ALT. And other tests for disease markers present at high levels in blood and urine are bound to follow.

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