Paper-based laser-pyrolyzed electrofluidics: an electrochemical platform for capillary-driven diagnostic bioassays

Abstract

Microfluidic paper-based analytical devices (uPADs) are indispensable tools for disease diagnostics. The integration of electronic components into uPADs enables new device functionalities and facilitates the development of complex quantitative assays. Unfortunately, current electrode fabrication methods often hinder capillary flow, considerably restricting uPAD design architectures. Here, we present laser-induced graphenization as an approach to fabricate porous electrodes embedded into cellulose paper. The resulting electrodes not only have high conductivity and electrochemical activity, but also retain wetting properties for capillary transport. We demonstrate paper-based electrofluidics, including (i) a lateral flow device for injection analysis of alkaline phosphatase in serum and (ii) a vertical flow device for quantitative detection of HPV16 with a CRISPR-based assay. We expect that this platform will streamline the development of diagnostic devices that combine the operational simplicity of colorimetric lateral flow tests with the added benefits and possibilities offered by electronic signaling.

Quantitative reagent monitoring in paper-based electrochemical rapid diagnostic tests

“…22 Within capillary-driven microfluidic devices, the use of electrodes for flow sensing has been restricted to detecting the flow front through changes in resistance or capacitance. 23,24 Although the flow front behaviour may serve as an indicator for RDT failure, 25 it cannot provide information on injected volumes or any aspect of multiinjection testing procedures. Several flow sensing solutions have been developed for pressure-driven microfluidic systems, 26 involving, for example, deformable membranes, 27 microstructures, 28,29 or microfabricated thermal sensors; 30 however, these microfabrication approaches are incompatible with paper-based systems.…”