For less than 10 cents to produce, researchers at the University of Texas at Austin have developed an origami-inspired paper sensor that may be able to test for complex diseases including malaria and HIV.
Cheap-to-produce paper sensors are not new, and are used for a variety of purposes — including home pregnancy tests — in order to track changes to chemical levels within a body. However, paper sensor technology is often hampered as it can only be used to detect more ‘basic’ changes in body composition — and have so far only generally included one-dimensional designs.
There is a group of researchers at the University of Texas who are not satisfied with these limitations.
Inspired by the traditional, Japanese art of paper-folding, origami-styled paper sensors have been developed that may be able to conduct more complex tests, dubbed the origami Paper Analytical Device (oPAD).
These low cost, ‘point of care’ 3D and strategically folded paper sensors are designed to test for more substances in a smaller surface area, and have been developed by Professor Richard Crooks and doctoral student Hong Liu. The paper sensors can be printed on any ordinary printer, and take less than a minute to fold properly.
“This is about medicine for everybody,” said Crooks. “Anybody can fold them up. You don’t need a specialist, so you could easily imagine an NGO with some volunteers folding these things up and passing them out. They’re easy to produce, so the production could be shifted to the clientele as well. They don’t need to be made in the developed world.”
Not only can these designs be used in the West, due to their low cost and simplicity, it is possible that the paper sensors could be invaluable for projects and healthcare in developing countries, where expensive lab-based testing is often not available.
Based on the same principles as a home pregnancy test, a hydrophobic material — such as wax — is laid on to tiny rifts in chromatography paper. When a sample is being tested, such as urine or blood, the material channels the sample to spots on the paper where reagent tests are embedded.
In the same manner as pregnancy tests, if the sample’s test reacts, it may turn a specific color, or become fluorescent under a UV light — which can then be read by the human eye. Crooks said:
“Biomarkers for all kinds of diseases already exist. Basically you spot-test reagents for these markers on these paper fluidics. They’re entrapped there. Then you introduce your sample. At the end you unfold this piece of paper, and if it’s one color, you’ve got a problem, and if not, then you’re probably OK.”
Taking the sensor design further, the team added a simple, inexpensive battery to the sensor, so it can run tests that require small amounts of power. In a prototype experiment, Crooks and Liu used aluminium foil and a urine test for glucose levels. According to the team, it would only cost a few extra cents to include the battery, of which salt present in urine activates the battery when required.
Although new and sophisticated sensor technology is constantly being developed, it is rarely aimed at cheap production and ease of individual use, as well as simplistic development. If the paper sensor proves to be successful and viable to produce, it could become a real benefit in both Western biomedicine and for health improvements in developing countries.
Image credit: Alex Wang