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http://hdl.handle.net/11375/21465
Title: | Microfabricated pH, temperature, and free chlorine sensors for integrated drinking water quality monitoring systems |
Authors: | Qin, Yiheng |
Advisor: | Howlader, Matiar M. R. Deen, M. Jamal Haddara, Yaser M. |
Department: | Electrical and Computer Engineering |
Keywords: | Inkjet printing;Sensor;Water quality monitoring;pH sensor;Free chlorine sensor;Temperature sensor |
Publication Date: | 2017 |
Abstract: | The monitoring of pH and free chlorine concentration in drinking water is important for water safety and public health. However, existing laboratory-based analytical methods are laborious, inefficient, and costly. This thesis focuses on the development of an easy-to-use, sensitive, and low-cost drinking water quality monitoring system for pH and free chlorine. An inkjet printing technology with a two-step thermolysis process in air is developed to deposit palladium/palladium oxide (Pd/PdO) films as potentiometric pH sensing electrodes. The redox reaction between PdO and hydronium ions generates the sensor output voltage. A large PdO percentage in the film provides a high sensitivity of ~60 mV/pH. A defect-free Pd/PdO film with small roughness contributes to a fast response and a high stability. When the Pd ink is thermalized in low vacuum, the deposited Pd/PdO film shows a bilayer structure. The residual oxygen in the low vacuum environment assists the decomposition of organic ligands for Pd to form a thin and continuous layer beneath submicron Pd aggregates. The oxidized bilayer film behaves as a temperature sensor with a sensitivity of 0.19% resistance change per °C, which can be used to compensate the sensed pH signals. Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is drawn by hand to form a free chlorine sensor. Free chlorine oxidises PEDOT:PSS, whose resistivity increment indicates the free chlorine concentration in the range of 0.5-500 ppm. Also, we simplified an amperometric free chlorine sensor based on amine-modified pencil leads. The simplified sensor is calibration-free, potentiostat-free, and easy-to-use. The pH, temperature, and free chlorine sensors are fabricated on a common substrate and connected to a field-programmable gate array board for data processing and display. The sensing system is user-friendly, cheap, and can accurately monitor real water samples. |
URI: | http://hdl.handle.net/11375/21465 |
Appears in Collections: | Open Access Dissertations and Theses |
Files in This Item:
File | Description | Size | Format | |
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Qin_Yiheng_201704_PhD.pdf | 6.26 MB | Adobe PDF | View/Open |
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