Demonstration of Reduced Power Consumption MEMS LEL Sensor Prepared by a Novel Digital Microfluid Technique

A low power consumption micro electro-mechanical system catalytic combustible low explosion limit (LEL) sensor was fabricated. The microheater was characterized by a suspending microhotplate over the silicon substrate. The alumina slurry and Pd-Pt catalyst solution were precisely and repeatedly coated on the microhotplate by a novel digital microfluid technique, respectively. Furthermore, the alumina layer and the alumina/catalyst layer on the microheater showed the collinear resistance versus voltage thermal characteristic curves during the solidification, which indicated that a good match could be directly made between them. During aging, the alumina/catalyst element demonstrated a high initial signal and then fell rapidly before coming to a stable value. Through pairing the alumina reference and alumina/catalyst sensitive elements in the wheatstone bridge, the output voltage could be up to 36 mV at the 50% LEL level of CH4 at the working temperature of 400
^°
C and the operation voltage was 2.6 V. The power consumption and the signal sensitivity could be also down to 75 mW and up to 0.702 mV/LEL%, respectively.