Purdue University/Aniket Pal
SPED plugged into a hand-held potentiostat Photo courtesy of
Researchers say they have developed self-powered, paper-based electrochemical devices (SPEDs) that can provide sensitive diagnostics in low-resource settings and at the point of care.
The SPEDs can detect biomarkers in the blood and identify conditions such as anemia by performing electrochemical analyses that are powered by the user’s touch.
The devices produce color-coded test results that are easy for non-experts to understand.
“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 V. Martinez, PhD, of Purdue University in West Lafayette, Indiana.
“We hope these devices will serve untrained people located in remote villages or military bases to test for a variety of diseases without requiring any source of electricity, clean water, or additional equipment.”
Dr Martinez and his colleagues developed the SPEDs and described them in a paper published in Advanced Materials Technologies.
SPED testing is initiated by placing a pinprick of blood in a circular feature on the device, which is less than 2-inches square. The SPEDs also contain “self-pipetting test zones” that can be dipped into a sample instead of using a finger-prick test.
The top layer of each SPED is made of untreated cellulose paper with patterned hydrophobic domains that define channels that wick up blood samples for testing. These microfluidic channels allow for assays that change color to indicate specific test results.
The researchers also created a machine-vision diagnostic application to identify and quantify each of these colorimetric tests from a digital image of the SPED, perhaps taken with a cell phone. This provides rapid results for the user and allows for consultation with a remote expert if necessary.
The bottom layer of the SPED is a triboelectric generator (TEG), which generates the electric current necessary to run the diagnostic test by rubbing or pressing it.
An inexpensive, hand-held device called a potentiostat can be plugged into the SPED to automate the diagnostic tests so they can be performed by untrained users. The battery powering the potentiostat can be recharged using the TEG built into the SPEDs.
“To our knowledge, this work reports the first self-powered, paper-based devices capable of performing rapid, accurate, and sensitive electrochemical assays in combination with a low-cost, portable potentiostat that can be recharged using a paper-based TEG,” Dr Martinez said.
SPEDs can perform multiplexed analyses, enabling the detection of various targets for a range of point-of-care testing applications. In addition, the devices are compatible with mass-printing technologies, such as roll-to-roll printing or spray deposition. And the SPEDs can be used to power other electronic devices to facilitate telemedicine applications in resource-limited settings.
Dr Martinez and his colleagues used the 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 anemia.
The researchers said future versions of the technology will contain several additional layers for more complex assays to detect diseases such as malaria, dengue fever, yellow fever, hepatitis, and HIV.
