Flexible Chemiresistive Chitosan‐Glycerol Sensors on Laser‐Induced Graphene Electrodes for Room‐Temperature Ammonia Detection

ABSTRACT We report a metal‐free sensor platform combining laser induced graphene (LIG) electrodes with drop‐deposited, glycerol‐plasticized chitosan biopolymer formulations for sustainable, chemiresistive detection of ammonia at room temperature. Increasing the glycerol v/v concentration from 2.5% to 7% yielded a logarithmic reduction (>400‐fold) in baseline device resistance (R ₀ ) at 60% RH. Devices fabricated using 5% glycerol showed chemiresistive response, ΔR/R ₀ = −16% ± 1% (n = 4) at 79 ppm NH ₃ (∼60% RH) with linear range 5–45 ppm and limit of detection ∼6–8 ppm. Chitosan‐LIG devices showed excellent selectivity for ammonia over other volatile organic compounds (VOCs), with concentration‐normalized responses for ammonia exceeding those of other VOCs by factors of 25–80. Devices showed minimal hysteresis (<2% cycle‐to‐cycle variation); good repeatability (ΔR/R ₀ ∼19% ± 1.5% at 79 ppm; 20 cycles), and excellent stability over six weeks (R ₀ = 3.41–3.53 MΩ, ΔR/R ₀ = −8% ± 2%, for 18 ppm NH ₃ . Flexibility tests (1500 cycles) showed ≤20% baseline drift and <3% variation in ΔR/R ₀ , highlighting the potential for future flexible or wearable devices. Finally, proof‐of‐concept monitoring in high‐humidity environments (∼85% RH), showed chemiresistive signatures for fish spoilage, with ΔR/R ₀ ∼ −46% ± 14% for devices mounted above ∼20 g fish in 5 mL water vs. ΔR/R ₀ ∼+21% ± 10%, for reference devices (water only).