Ultra-low-power semiconductor gas sensors for Internet of things applications

• Main Author: Saif Abdulla Ali Mubarak Alateeqi
• Other Authors: Liu Aiqun
• Format: Theses and Dissertations
• Language: English
• Published: 2018
• Subjects: DRNTU::Engineering::Electrical and electronic engineering
• Online Access: http://hdl.handle.net/10356/76086
• Institution: Nanyang Technological University

Semiconductor Metal Oxide (MOX) gas sensors based on Micro-Electromechanical Systems (MEMS) technology show great promise for consumer electronics and Internet of Things (IoT) applications because of their low power, cost-effectiveness, ultra-compact footprint, high volume manufacturability, and suitable lifetimes. However, such applications have stringent requirements for power consumption making it a bottleneck. The micro-hotplate is a critical component of MOX gas sensor operation and consumes >90% of the total power. This thesis discusses three platinum-based gas sensor micro-hotplate designs: large double spiral, small double spiral, and circular. The designs were simulated, fabricated, and tested. The small spiral, coded HT002, showed a low power consumption, 35 mW for 300 °C operation, a temperature widely used for gas sensing. Power loss dispersion was measured, and the heat conduction losses were found to be the dominant contributor to power consumption. Three sensor failure modes were identified: microcrack, peeling, and rupture. Then, the devices were functionalized with SnO2 to make Carbon Monoxide (CO) gas sensors. Gas testing was performed, and the CO gas sensor was used for detecting 25ppm CO. After, two ultra-low-power gas sensors are proposed: a straight beam and a long-U cantilever. The designs were analysed and simulated. Power consumption optimisation is presented for both designs. The beam and cantilever simulations show ultra-low-power of 460μW and 400μW for 300°C respectively. At the moment of writing, fabrication of the ultra-low-power beam and cantilever designs is underway. Such results could pave the way for enabling long lasting IoT gas sensing systems.