Design of Self-Powered Flexible Gas Sensors for Room Temperature NO2 Detection


Student thesis: Doctoral Thesis

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Awarding Institution
Award date18 May 2021


NO2 is one of the major contaminants released from the combustion of fossil fuels by automobiles and power plants. It is harmful to the environment and human health. Exposures can aggravate respiratory diseases, particularly asthma, leading to respiratory symptoms. Wearable/portable NO2 sensor is in great demand for real-time analysis of NO2 in air. To make portable electronics, several requirements should be fulfilled, such as flexibility, compact design, and low power consumption.

The thesis presents the design of flexible and self-powered gas sensors for room temperature NO2 detection. First, a convenient way to fabricate interdigital electrodes (IDE) on flexible substrate was investigated. Using a well-controlled laser, IDE with good electrical and mechanical performances could be fabricated on a polyimide (PI) film. A chemiresistive NO2 gas sensor using MoS2 as the sensing material was studied using this IDE. The influence of MoS2 size on gas sensing properties is also studied. By controlling the size of the MoS2 sphere, optimal sensing property was achieved, balancing sensitivity and response time. Overall, high performance in gas sensing combined with low susceptibility to mechanical damage enables the sensor to serve a variety of wearable sensory applications.

Secondly, a new paradigm for self-powered gas sensing is investigated. To achieve miniaturization, single module with multiple functions is desirable. Based on a typical zinc-air battery structure, a self-powered electrochemical NO2 gas sensor was designed. The sensor-battery hybrid device shows both good gas sensing performance and eliminates the need for battery replacement and energy harvesting. As a demonstration, an energy self-sufficient gas sensor has been fabricated and characterized. In addition to excellent sensitivity and selectivity provided by catalysed electrochemical reaction at the cathode, this flexible sensor shows excellent robustness against mechanical deformation and can sustain substantial damage, which is especially advantageous for wearable applications.

In summary, chemiresistive and electrochemical gas sensors have been developed for room temperature NO2 gas sensing. Several properties have been achieved such as high response, good flexibility, self-power, excellent selectivity. It is believed that these studies can provide a new paradigm for wearable and portable gas sensing.