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Origami paper sensor could detect malaria, HIV for 10 cents

Researchers say their 3D point-of-care sensor, called oPad, can be printed on a simple office printer.

The oPAD can be assembled in less than a minute for less than a dime.
Alex Wang

Affordable paper sensors aren't exactly new. Think home pregnancy tests. But researchers out of the University of Texas at Austin are pushing (or is it folding?) the envelope with their origami-inspired 3D paper sensor that, thanks to strategic folding, can identify more substances in more complex tests.

Able to be printed at less than a dime a sensor using an ordinary office printer and less than a minute of folding, the origami Paper Analytical Device (which they've dubbed oPAD) "is about medicine for everybody," said Richard Crooks, a chemistry professor who built the sensor with doctoral student Hong Liu, in a school news release.

Liu was first inspired to use origami when he read a paper by Harvard chemist George Whitesides, who is the first to build a 3D microfluidic paper sensor to target biological agents.

"They had to pattern several pieces of paper using photolithography, cut them with lasers, and then tape them together with two-sided tape," Liu said. "When I read the paper, I remembered when I was a child growing up in China, and our teacher taught us origami. I realized it didn't have to be so difficult...Just fold the paper, and then apply pressure."

Liu and Crooks applied the principles of the home pregnancy tests, where a hydrophobic material such as wax is laid down on chromatography paper, to direct whatever sample is being tested (i.e. urine, saliva, blood) to spots on the paper that are embedded with test reagents.

Then, in the event the sample contains whatever is being targeted (glucose, malaria, HIV, etc.), a specific reaction occurs, such as the paper turning a certain color or showing two lines instead of one. Because biomarkers already exist for a wide range of diseases, all the duo had to do was test the paper fluidics.

"You introduce your sample [and] unfold this piece of paper, and if it's one color, you've got a problem, and if not, then you're probably OK," said Crooks, whose findings appear in the journal Analytical Chemistry.

Crooks and Liu have taken the sensor a step further by adding a tiny, simple battery to their sensor for tests that require power. They estimate that this simple battery would raise the cost of the sensor by a few cents, and that urine contains enough salt to act as an electrolyte for the battery, thus activating it.

New sensors to detect various diseases and biological agents are being built all the time, but rarely does one solve the problem of cost, ease of use (where the end user doesn't have to run a sample to a lab for results), and even ease of development (simply printing and folding). Time and testing will tell if the oPAD can reliably detect diseases such as malaria and HIV; if it can, it really will be "about medicine for everybody."