A new medical diagnostic device made of paper detects biomarkers and identifies diseases by performing electrochemical analyses — powered only by the user’s touch — and reads out the color-coded test results, making it easy for nonexperts to understand.
The self-powered, paper-based electrochemical devices (SPEDs) are designed for sensitive diagnostics at the point-of-care, or when care is delivered to patients, in regions where the public has limited access to resources or sophisticated medical equipment. The test is initiated by placing a pinprick of blood in a circular feature on the device, which is less than 2” square. 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 the SPED is fabricated using untreated cellulose paper with patterned hydrophobic domains that define channels that wick up blood samples for testing. These microfluidic channels allow for accurate assays that change color to indicate specific test results. A machine-vision diagnostic application also was created 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 tri-boelectric generator (TEG) that generates the electric current necessary to run the diagnostic test simply by rubbing or pressing it. The researchers also designed an inexpensive handheld device (a potentiostat) that is easily 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.
SPEDs are compatible with mass-printing technologies such as roll-to-roll printing or spray deposition. They can perform multiplexed analyses, enabling the highly sensitive and accurate detection of various targets for a range of point-of-care testing applications. They also can be used to power other electronic devices to facilitate telemedicine applications in resource-limited settings.
The SPEDs were used 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. 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.