Digital Microfluidics Increases Complexity of Paper Diagnostics

Complex multiplex and multistep assays have traditionally posed a challenge for paper-based microfluidic diagnostic devices. However new research shows that paper-based digital microfluidics (DMF) devices have comparable performance to photolithographically patterned chromium-on-glass DMF devices at a fraction of the cost, according to a study published in Advanced Materials. DMF involves manipulating liquid drops on an array of electrodes using electrostatic forces. A challenge in their application is a lack of scalable, cost-effective device fabrication. University of Toronto researchers showed that using an inkjet printer and silver nanoparticle-based ink they could create a paper DMF device that is capable of performing a homogeneous chemiluminescence assay that requires 22 discrete steps, which the authors say would be “difficult or perhaps impossible” to perform on a capillary-driven paper device. “DMF is emerging as a useful tool for implementing fully automated, low-volume magnetic particle-based immunoassays, and we propose that paper-based DMF devices could make this diagnostic method feasible for resource-poor settings,” write the authors, led by Ryan Fobel. For more information on the re-emergence of interest in paper-based point-of-care diagnostics, please see Inside the Diagnostics Industry on page 5.