Seamless Integration of Laser-Induced Papertronics with Parafilm-Based Microfluidics as a Versatile Paper-Based Electroanalytical Platform

The widespread use of nonrenewable materials in point-of-care (PoC) electroanalysis, such as test strips with electronic meters, has inadvertently contributed to electronic waste. Paper, traditionally used as a passive substrate, offers a renewable alternative as a sustainable and versatile electroanalytical platform for on-site analysis. Here, we present the fabrication and integration of laser-induced electronic components and Parafilm-based microfluidics on a single sheet of paper as a versatile electroanalytical platform for both aqueous and organic systems. Using a flame retardant and laser treatment, we enable a direct conversion of passive cellulose paper into laser-induced graphite (PLIG), allowing for the fabrication of conductive pathways and various electronic components with customized geometries on a single sheet of paper, a process termed laser-induced papertronics. Microfluidic channels were then successfully patterned by hot-pressing hydrophobic Parafilm into hydrophilic cellulose paper (paper-para) at a low temperature (60 °C) for just 15 s, achieving a submillimeter resolution of ∼0.45 mm. The resulting paper-para demonstrated compatibility with a wide range of aqueous solutions and organic solvents. This process facilitates the seamless integration of laser-induced papertronics with Parafilm-based microfluidics on a single monolithic paper sheet, denoted microfluidic PLIG (μPLIG), preserving both the structural integrity and electrochemical performance of the papertronics as well as the fluidic character of the Parafilm-based paper microfluidics. Demonstrative applications include pH sensing with a sensitivity of -40.3 mV pH^-1, lactate biosensing with a sensitivity of 0.92 μA mM^-1, and Vitamin D3 detection in ethanol mixtures exhibiting a linear range of 5-65 μM, indicating the platform's compatibility and versatility for sensor applications in both aqueous and organic systems. This study establishes a foundation for a uniquely integrated, cost-effective, and environmentally friendly electroanalytical platform, μPLIG, uniting paper-based LIG electronics and Parafilm-based microfluidics on a single disposable substrate.