IoT-Based Laser-Inscribed Sensors for Detection of Sulfate in Water Bodies

This paper presents the fabrication of novel flexible sensors from metalized polymer films and their subsequent utilization for environmental applications. Polyethylene terephthalate films coated with thin-film of aluminum was used as a singular material to form the sensor patches. Optimization was done on the laser parameters to form laser-inscribed interdigitated electrodes on the aluminum side of the polymer films. The sensors were then used to detect the presence of sulfate ions in the water samples. Electrochemical impedance spectroscopy was used to detect the resistive and reactive changes with respect to the corresponding changes in the concentration of the tested solutions. Experiments were conducted using five different concentrations ranging between 0.1 ppm and 1000 ppm. The sensitivity, limit of detection and response time of the salts were 0.874~\Omega /ppm, 0.1 ppm and one second, respectively. The repeatability of the sensors was also tested to validate their responses for the target analyte. An optimal frequency was chosen to form an IoT-based system that consisted of an impedance analyzer AD 5933, Wi-Fi embedded Arduino and 2:1 multiplexer ADG849. The interfacing of the microcontroller-sensed data was also done with the cloud server to showcase the potentiality of the developed systems as portable devices for real-time applications.