Real-Time Amperometric Monitoring of Nicotine in Smoke Streams Using Three-Dimensional-Printed Microelectrode Sensors

A real-time electrochemical sensing strategy for nicotine monitoring in smoke streams was developed using additively manufactured three-dimensional (3D) based on conductive polymer composites. Disc-type microelectrodes (3.0 mm diameter) were fabricated by fused filament fabrication using carbon black/polylactic acid (CB/PLA) and multi-walled carbon nanotube/polylactic acid (MWCNT/PLA) filaments, followed by systematic post-printing surface engineering via electrochemical activation and CO₂ laser ablation. Comprehensive materials characterization confirmed that laser ablation most effectively removed the insulating PLA matrix and generated a highly porous, defect-rich carbon surface, leading to pronounced enhancement in electrochemical kinetics. The laser-ablated MWCNT/PLA electrode exhibited near-reversible redox behavior for the Fe(CN)₆³⁻/⁴⁻ probe with a peak-to-peak separation of 68 mV and a markedly reduced charge-transfer resistance of 85 Ω, compared to >4000 Ω for pristine electrodes. Nicotine oxidation at the optimized electrode occurred irreversibly at approximately +0.85 V vs. Ag/AgCl and followed diffusion-controlled kinetics. Differential pulse voltammetry enabled quantitative nicotine detection over a linear range of 0.1–100 µM with a sensitivity of 6.37 µA·µM⁻¹·cm⁻² and a low limit of detection of 30 nM. In a custom-built aerosol chamber, the sensor delivered rapid amperometric responses with stabilization times below 5 s and reliably quantified vapor-phase nicotine from 20 to 100 ppb. The device showed high selectivity, with interference signals below 4% even at tenfold excess of common interferents, excellent reproducibility (relative standard deviation (RSD) 3.8%, n = 5), and retained 95.2% of its initial response after 30 days. Real cigarette smoke measurements further demonstrated clear discrimination between light and full-flavor products, with results agreeing with HPLC analysis within 7%, underscoring the platform’s suitability for practical exposure assessment.