High-performance MEMS ethanol sensor based on WO3-RuO2 nanomaterials

Ethanol metabolism is a pivotal secondary metabolic process in post-harvest fruit storage, serving as a key indicator of freshness. However, the complex mixture of gases (e.g., CO 2 , aldehydes, esters, and alcohols) released during fruit ripening necessitates sensors with high selectivity and sensitivity specifically toward ethanol. This study presents a high-performance micro-electro-mechanical system (MEMS) ethanol sensor based on WO 3 -RuO 2 nanomaterials synthesized via a simple and low-cost solvothermal method. The optimized sensor with a Ru mass ratio of 1 wt% operates at a low voltage of 1.5 V (200 °C) with a power consumption of only 25 mW. It exhibits a high response of 53.3 toward 100 ppm ethanol, approximately seven times greater than that of a pure WO 3 sensor, along with a low detection limit of 50 ppb. Notably, the sensor demonstrates excellent selectivity against common fruit-emitted interferents (e.g., ethyl acetate and CO 2 ) as well as other alcohols and structurally similar gases. The sensing mechanism was investigated through multiple complementary techniques, including in situ Raman spectroscopy, Mott-Schottky measurements, UV–Vis DRS, and UPS. Furthermore, an artificial neural network (ANN) model, validated by confusion matrices, successfully classified the freshness of mango and peach, confirming the sensor's practical capability for daily spoilage assessment and prediction.