3D printing pen for patterning electrochemical sensors on a paper platform for capsaicin detection

The development of a print-at-home, low-cost, and miniaturized paper-based cell with 3D-printed electrodes using a 3D-printing pen and a bespoke conductive filament for detecting capsaicin in hot sauce is reported herein. The material cost of producing each electrode was less than £0.01. The new filament was electrochemically benchmarked against a commercial CB/PLA conductive filament. The CB/graphite/recycled PLA filament molded in paper platform produced a heterogeneous rate constant, k0obs, of 1.64 (± 0.13) × 10^-3 cm s^-1 and resistance of only 166 ± 0.13 Ω compared to 0.43 (± 0.05) × 10^-3 cm s^-1 and 1613 ± 220 Ω for an identical device printed from commercial CB/PLA filament. The newly developed device using the bespoke filament on kraft paper was applied successfully to detect capsaicin (CAP). CAP showed a characteristic peak at approximately +0.7 V for the bespoke CB/graphite/rPLA filament in cyclic voltammetry. A small peak at +1.0 V is observed when using the commercial filament. Additionally, a linear range of 5 to 20 μM and a sensitivity of 0.0093 μA μM was obtained for CAP when applying differential pulse voltammetry using the paper-based device with the bespoke filament. Limits of detection and quantification were calculated at 1.21 and 3.98 μM, respectively. The new system quantifies CAP in a commercial red pepper hot sauce (Tabasco). This work highlights how a low-cost kraft paper platform and a bespoke conductive filament can be combined to create an effective electrochemical device using simple tools for quantifying capsaicin in real samples. Additionally, it highlights the potential of these materials and techniques to develop home-based sensors.