Design and application of miniature multi-parameter water quality sensor chip

Water-quality sensors feature a single measurement function and are greatly affected by ambient temperature. This paper proposes a multi-parameter water-quality sensor chip with temperature compensation. The sensor chip was manufactured using the micro-electro-mechanical system (MEMS) technology. The chip surface contained integrated pH, dissolved oxygen (DO), ammonia-nitrogen, and temperature sensors. To achieve temperature compensation, the chip was also designed with a sandwich-plate snake Pt resistance heater. At the same time, a microfluidic test chamber that was matched with the chip was designed to realize water-sample measurement. Finite-element steady-state thermal analysis was used to analyze the heat-transfer process of four heaters, and a reasonable chip-structure layout was established. Thereafter, the sensor chip was fabricated using the MEMS technology. The performance of the sensor chip was investigated using a laboratory-developed potentiostat test circuit. Experimental results show that the pH sensor has a high sensitivity of 0.288 mA/pH.The sensitivity of the temperature sensor is 0.949 Ω/℃ and that of the ammonia-nitrogen sensor was 0.113 9 mA/(mg•L-1). The sensitivity of the DO sensor is 2.22 μA/(mg•L-1) and that of the temperature sensor, which changes with respect to the heater power, is 0.312 6℃/mW. Compared with a single water-quality parameter sensor, the as-prepared sensor chip could simultaneously detect multiple parameters of a water sample and exhibited a good temperature-compensation effect. Moreover, the sensor chip was small in size, robust, and highly accurate. © 2020, Science Press. All right reserved.