Solid-state, vertically stacked, semi-open electrochemical cells to build compact and highly sensitive biosensors

This work presents the performance of a semi-open electrochemical cell (SOEC) for potentiometric biosensing. In this design, the electrodes are vertically stacked, and a solid-state polyelectrolyte is used as separator. This paper-based device requires a minimal sample volume, as only the top working electrode contacts the solution while the reference electrode remains shielded in the bottom of the cell. Using a paper-based Pt working electrode, the system demonstrates high sensitivity to hydrogen peroxide with linear response below 10 µM and a Tafel slope of 120 mV/decade at higher concentrations. Electrode area optimization enables tunable analytical performance by controlling sensitivity and linear ranges. The device exhibits exceptional stability, with a baseline noise level below 0.1 mV and low impedance, facilitating integration with simple operational amplifiers. This design achieves ultralow detection limits for hydrogen peroxide (~10 nM) using only 1 µL sample volumes and maintains linearity up to 10 mM. When coupled with oxidase enzymes, the system enables rapid and versatile glucose testing in artificial serum and sweat using single sample drops, with absolute limits of detection in the µM range. This compact, versatile paper-based platform offers promising opportunities for developing wearable, disposable biosensors for point-of-need applications. • Vertically-stacked electrochemical sensor with exceptional stability and broad range of detection • Tunable analytical performance through electrode area optimization • 10-fold signal enhancement via non-inverting operational amplifier integration • Nanomolar detection limits in single-microliter samples • Reliable glucose quantification in artificial serum and sweat from single drops