Wireless Ammonia Gas Sensor based on P-type Porous Si: Methods, Materials and Design
Abstract
This study investigates the 4S performance parameters (selectivity, sensitivity, stability, speed) of a porous silicon (PS)-based gas sensor and develops a portable, wireless electronic device for ammonia detection. The porous silicon layer was fabricated by electrochemically etching p-type (100) crystalline silicon using a hydrofluoric acid (HF) and ethoxyethanol electrolyte in a 1:2 volume ratio. A compact sensor module was developed, integrating a comparator circuit, Wi-Fi connectivity, a web-based monitoring platform, and the PS sensing element, fabricated using a ProtoMat E44 CNC plotter and housed in a 3D-printed PLA enclosure. The optimized sensor exhibited a high sensitivity of 42% to ammonia, surpassing responses to other gases. The system leverages an ESP32 microcontroller for real-time data acquisition, enabling remote monitoring via a custom IoT platform with email/SMS alerts for gas concentration thresholds. The results validate the feasibility of room-temperature operation, eliminating the need for heating elements while maintaining rapid response (20 s) and stability over 10 days. This work advances the development of low-power, portable gas sensors for environmental and industrial safety applications.