Drop-coated metal-oxide gas sensor on polyimide foil with reduced power consumption for wireless applications

Highly miniaturized low-power drop-coated metal-oxide gas sensors on polyimide foil are presented. Drop-coating of SnO2-based material was successfully achieved on transducers as small as 15 mu m on polyimide, a substrate compatible with the printed electronics industry. The sensors showed a very good chemoresistive response when exposed to CO and NO2. The power consumptions of the sensors ranged from a minimum of 7.7 mW for the smallest hotplate at 200 degrees C to a maximum of 28.4 mW for the largest device at 250 degrees C in continuous mode of operation. In a pulsed mode, their consumption was reduced to the sub-milliwatt range for the 15 mu m wide heaters while keeping a good chemoresistive response, widening their use to low-power applications, such as for wireless systems. The sensors were interfaced to a custom-made electronic circuitry with a readout based on time-to-digital conversion to minimize the amount of electronic components and reduce the power consumption. The power consumption of the 15 mu m wide sensor was 680 mu W in pulsed mode, while the sensor system exhibited a total power consumption of 1.9 mW. (C) 2011 Elsevier B.V. All rights reserved.