Ionogel sensor for reproducible detection of trace methamphetamine analogues

Drug detection is highly important, yet reversible and highly sensitive sensing materials are still scarce. A novel ionogel sensor material, poly(ethylene glycol) diacrylate (PEGDA)/1-butyl-3-methylimidazole tetrafluoroborate, was developed for reproducible N-methylphenylethylamine (MPEA) detection. It was fabricated by immobilizing a flowable ionic liquid within a PEGDA network via UV curing. The immobilized ions retain mobility, enabling efficient ionic conduction. Integrated on a flexible poly(ethylene naphthalate) substrate, the sensor is fully transparent and flexible, showing over 72.6% transmittance in the visible spectrum. This allows it to be discreetly attached to surfaces for concealed detection. Using non-covalent interactions, the sensor achieves reproducible MPEA detection at sub ppb levels at room temperature, with a theoretical detection limit of 317 ppt. It also exhibits high selectivity and consistency. Ionic conductivity was confirmed through current voltage tests and impedance spectroscopy, and the sensing mechanism was clarified. The device performs reliably under bending, proving suitable for dynamic environments. With a Bluetooth module for wireless transmission, the sensor shows strong potential for practical and discreet drug monitoring in real world applications.