研究目的
To enhance the sensor sensitivity towards formaldehyde and ethanol, as well as to improve the baseline stability of the gas sensor response at low power consumption.
研究成果
The novel composite heater design improved sensitivity and baseline stability compared to the D02 design at low power consumption. However, operation in heat pulsing mode led to decreased sensitivity over time, and smartphone cases caused interference similar to reducing gases. Future work should focus on enhancing selectivity and further reducing power consumption.
研究不足
The study notes limitations such as the adverse impact of heat pulsing mode on sensor reliability due to thermal stress and crack formation, poor selectivity and temporal drift of SMO sensors, contamination from smartphone cases affecting sensor performance, and the need for further power consumption reduction without using heat pulsing mode for wearable applications.
1：Experimental Design and Method Selection:
The study involved designing and fabricating SMO gas sensors with a novel composite heater structure. Simulations using COMSOL Multiphysics were conducted for thermal and mechanical analyses. Experimental characterizations included sensing performance tests for VOCs, dynamic response in heat pulsing mode, and effects of smartphone cases.
2：Sample Selection and Data Sources:
Two sensor designs (D02 and composite heater) were fabricated and tested. Gas concentrations (formaldehyde and ethanol from 100 ppb to 5 ppm) were controlled in a micro-chamber. Data on resistance and sensitivity were collected.
3：List of Experimental Equipment and Materials:
Equipment included Keithley 2450 SourceMeters, environmental chamber, micro-chamber, valves, PC for data control, ASIC, test board, canary board with STM32, Bluetooth module, temperature sensor, LCD display, and smartphone cases. Materials included TaAl microheater, Pt-doped SnO2 sensing layer, porous silicon nitride membrane, AlCu conductive pads.
4：Experimental Procedures and Operational Workflow:
Sensors were fabricated by etching openings in AlCu pads. Sensing tests involved exposing sensors to gases at controlled concentrations, measuring resistance changes. Heat pulsing mode tests used on-off cycles. Smartphone case tests involved placing cases near sensors in open air and closed chambers, monitoring resistance.
5：Data Analysis Methods:
Data were analyzed using the Langmuir adsorption model for sensitivity fitting. Statistical analysis of reproducibility and baseline stability was performed. Simulations provided temperature and stress distributions.
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