Abstract
This study developed an electronic-nose sensor node based on a polymer-coated surface acoustic wave (SAW) sensor array. The sensor node comprised an SAW sensor array, a frequency readout circuit, and an Octopus II wireless module. The sensor array was fabricated on a large K2 128° YX LiNbO3 sensing substrate. On the surface of this substrate, an interdigital transducer (IDT) was produced with a Cr/Au film as its metallic structure. A mixed-mode frequency readout application specific integrated circuit (ASIC) was fabricated using a TSMC 0.18 μm process. The ASIC output was connected to a wireless module to transmit sensor data to a base station for data storage and analysis. This sensor node is applicable for wireless sensor network (WSN) applications.
Highlights
Wireless sensor networks (WSNs) [1,2] comprise a number of light-weight low-power sensor nodes.Each node is equipped with a number of sensors, interface electronics, and a wireless communication module to deliver the collected data
The sensing mechanism is based on the fact that volatile organic compounds are adsorbed on the surface of a substrate and an increase in mass loading causes a shift in frequency
To verify the Electronic nose (E-Nose) sensor node, three tests had to be performed: (1) a gas experiment to validate the surface acoustic wave (SAW) sensor array; (2) a configuration test to verify the accuracy of the mixed-signal readout chip; (3) a verification test to determine the correctness of the wireless transmission
Summary
Wireless sensor networks (WSNs) [1,2] comprise a number of light-weight low-power sensor nodes. A change in mass on the active sensing region can be detected, according to changes in magnitude and phase shift in the AC signal between the input and output IDTs. To increase the selectivity and sensitivity of the sensor, a variety of polymers are used to coat the active sensing region of the SAW sensors to absorb molecules of the target gas. E-Nose system has been to connect the SAW array to a spectrum analyzer or a frequency counter to monitor frequency shifts in the SAW devices Neither of these options is practical for portable or WSN applications, due to their bulk and high price. We report an efficient E-Nose sensor node comprising a 2 2 non-continuous chemical SAW sensor array chip using MEMS technology self-assembled with polymer coatings on the active sensing region [20,21], application specific integrated circuit (ASIC) chip for a mixed signal interface, and a WSN platform (Octopus II).
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