Self-powered, paper-based device can detect diseases

Scientists, including those of Indian origin, have developed a new portable, paper-based device that can identify diseases such as anaemia and can be powered just by rubbing or pressing it.

Researchers at Purdue University in the US built self- powered, paper-based electrochemical devices (SPEDs) can provide sensitive diagnostics to patients in regions that have limited access to resources or medical equipments.

The device detects biomarkers and identifies diseases by performing electrochemical analyses and reads out the colour- coded test results, making it easy for non-experts to understand, researchers said.

The test is initiated by placing a pinprick of blood in a circular feature on the device, which is less than two square inches. SPEDs also contain "self-pipetting test zones" that can be dipped into a sample instead of using a finger-prick test, researchers said.

The top layer of the SPED is fabricated using untreated cellulose paper with patterned hydrophobic "domains" that define channels that wick up blood samples for testing.

These channels allow for accurate assays that change colour to indicate specific testing results. They also created a machine-vision diagnostic application to automatically identify and quantify each of these "colorimetric" tests from a digital image of the SPED, perhaps taken with a cellphone, to provide fast diagnostic results to the user and to facilitate remote-expert consultation.

The bottom layer of the SPED is a "triboelectric generator," or TEG, which generates the electric current necessary to run the diagnostic test simply by rubbing or pressing it, researchers said.

Researchers, including Debkalpa Goswami and Aniket Pal, designed an inexpensive handheld device called a potentiostat, which is easily plugged into the SPED to automate the diagnostic tests so that they can be performed by untrained users.

The battery powering the potentiostat can be recharged using the TEG built into the SPEDs. Researchers used SPEDs to detect biomarkers such as glucose, uric acid and L-lactate, ketones, and white blood cells, which indicate factors related to liver and kidney function, malnutrition and anaemia.

Future versions of the technology will contain several additional layers for more complex assays to detect diseases such as dengue fever, yellow fever, malaria, HIV and hepatitis, Martinez said.

"You could consider this a portable laboratory that is just completely made out of paper, is inexpensive and can be disposed of through incineration," said Ramses Martinez, an assistant professor at Purdue University. The study was published in the journal Advanced Materials Technologies.