HIGHLY SELECTIVE MEMS AMMONIA GAS SENSOR FOR RENAL FAILURE SCREENING AND MONITORING HEMODIALYSIS ENDPOINT

• Main Author: ABDALRAHMAN AHMED, MAWAHIB GAFARE
• Format: Thesis
• Language: English
• Published: 2017
• Subjects: Instrumentation and Control
• Online Access: http://utpedia.utp.edu.my/id/eprint/22036/1/Mawahib_Gafare_final_thesis_G01981.pdf; http://utpedia.utp.edu.my/id/eprint/22036/

Breath gas analysis provides a way to diagnose diseases by detection of special odors in the breath. It has been proven as a non-invasive tool for diagnosis. Some gases from breath have been determined to be highly characteristic of specific diseases. For instance, patients with renal failure exhaled ammonia gas with a higher concentration than the normal level, because their kidneys failed to purify the blood from waste materials. This dissertation reports the design, analytical modeling, simulation, fabrication, and characterization of a MEMS ammonia gas sensor for screening renal failure and determining hemodialysis endpoint. The sensor is designed and fabricated following the standard PolyMUMPs process technology. The device is operated in dynamic mode using electro-thermal actuation method and capacitive sensing technique is used to measure the output voltage via MS3110 universal readout circuit. A sensitive and selective material (PANI/MWCNTs/TiO2 nano-composite) is coated on top of the moving plate. The mass of the moving plate changes according to the amount of ammonia gas molecules adsorbed on the sensitive coating material. The theoretical parameters of the device are derived based on analytical modeled equations, verified with simulation and validated experimentally. Experimental results show that the sensor is capable of detecting ammonia gas in air with concentration ranging from a lower detection limit of 1 ppm to 10 ppm. This is within the range of 2 ppm and above for the abnormal level of ammonia in exhaled breath of patients with renal failure. The sensitivity of the sensor is found to be 17.85 mV/ppm after amplification and 0.088 mV/ppm prior to amplification. Finally, the response of the sensor is measured towards various gases found in the exhaled breath including 89.80 %RH relative humidity, 10 ppm of acetone, methanol, and ethanol concentration. The sensor is found to be highly selective towards ammonia gas compared to the other gasses. The response of the sensor is found to be 0.78 mV/s while the recovery is found to be 0.67 mV/s.