Micro catalytic methane sensors based on 3D quartz structures with cone-shaped cavities etched by high-resolution abrasive sand blasting

A novel quartz based micro catalytic methane sensor with back-etched cone-shaped cavity was fabricated by high-resolution abrasive sand blasting technique. Highly uniform micro cavities were easily and quickly achieved with a depth of 450 μm and a bottom diameter of 600 μm on a quartz substrate 500 μm thick, followed by screen printing porous alumina with a position accuracy of 10 μm and inkjet printing of co-metal catalyst with loading quantity resolution of 4.75 ng. Compared with a bulk quartz substrate sensor, performance of the sensor fabricated by abrasive sand blasting is greatly improved with a lower thermal mass. The sensor's temperature distribution profile is more concentrated on target catalyst, power consumption decreases to 285 mW by 23%, thermal response time decreases to 8.8 s by 79%, and sensitivity to methane increases to 1.83 mV/% CH4 by 35%, with a high correlation coefficient up to 0.9986. Moreover, this sensor demonstrates excellent resistance to mechanical shock at high working temperatures, significantly superior to conventional silicon based membrane sensors. This design of the high performance sensor, together with the simple and fast MEMS-compatible fabrication process enables such catalytic sensors for mass production and combustible gas detecting in harsh environmental applications.