Fabrication of a laser-directed electrochemical paper analytical device and its deployment for multi-functional electrochemical sensing

The demand for eco-friendly, disposable, and affordable electrochemical sensors stimulates the fabrication of laser-directed paper-based electrodes. This work reports the fabrication of laser-derived patterns on the paper substrate and its multi-functional sensing applications. For this, a computer-aided design (CAD) software-driven computer numerical control (CNC) manufacturing method was developed to engrave a three-electrode design on a paper substrate. The fabricated Laser-Directed electrochemical Paper Analytical Device (LD-ePAD) was thoroughly characterized by Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), contact angle analysis, electrochemical impedance spectroscopy (EIS), and the cyclic voltammetry (CV). After that, we demonstrated the multifunctional sensing ability of the LD-ePADs by detecting diverse model analytes, including small molecules (i. e., lead ions [Pb2+]), free radicals (i.e., peroxide [H2O2]), and macromolecules (i.e., Alkaline phosphatase [ALP]). Upon investigation, it exhibits a fair detection limit of 5.19 (+/- 0.21) mu M for Pb2+, 48.66 (+/- 0.31) mu M for H2O2, and 0.48 (+/- 0.02) U/L for ALP. The LD-ePADs' outstanding repeatability, stability, abundance of catalytic active sites, remarkable tunability, and potential for nano-bioengineering emphasized their tremendous commercial feasibility. To the best of our knowledge, this is the first study to use controlled one-step laser direct engraving to fabricate a three-electrode setup on a paper-substrate that can sense three heterogeneous molecules electrochemically.