A.V. Pisliakov

Metal-oxide gas sensor high-selective to ammonia

Metrological and performance characteristics of a metal-oxide sensor high-selective to ammonia in the presence of methane, carbon monoxide, and water vapors are presented. The specific feature of the design consists in using pulsed sensor heating as the main factor for improved selectivity to ammonia. The ammonia threshold achieved during the pulse-type temperature modulation is 5 × 10−4% vol.

Sensors Based on Technology “Nano-on-Micro” for Wireless Instruments Preventing Ecological and Industrial Catastrophes

The problem of gas analyzers compatible with wireless networks can be solved by using sensors based on the “nano-on-micro” technology. The basis of this technology consists in nano-composite sensing metal oxide semiconductor or thermocatalytic materials deposited on a microhotplate fabricated using silicon or alumina microelectronic technology. As a result, the sensor combines the advantages of both technologies: on the one hand, high stability and sufficient selectivity of nano-composite materials, and, on the other hand, microprocessor compatibility, low-cost, mass-production possibilities, and low power consumption of microelectronic substrates. Two methods for the fabrication of microhotplates are the most promising: the silicon based technology of silicon oxide/silicon nitride membranes and the CeraMEMS technology of thin alumina films (TAF). The first technology enables the fabrication of microheaters with a power consumption around 20 mW for an operating temperature below 450°C. Advantages of CeraMEMS platforms are: (1) operation at temperature up to 600°C and, potentially, up to 800°C; (2) robustness compared with silicon chip with thin membrane; (3) perfect Pt and sensing layer adhesion without any adhesive layers; (4) low cost of middle scale production (104–107 chips per year) compared with the silicon technology. The CeraMEMS platform can be used for the fabrication of semiconductor and thermocatalytic gas sensors, as a source of IR radiation for optical gas sensors and as bolometers. The sensor withstands ∼7 × 106 on-off cycles. Heater resistance drift is below 3% per year at 550°C.

Gas sensors based on MEMS structures made of ceramic ZrO2/Y2O3 material

The methods of the fabrication of MEMS platforms based on yttria stabilized zirconia (YSZ) and alumina membranes for gas sensors used in harsh environmental conditions are described. It is shown that the application of such membranes permits a decrease in MEMS power consumption at 450°C down to ~75 mW at continuous and down to ~ 1 mW at pulse heating of gas sensor.

Automotive MEMS sensors based on additive technologies

The application of MEMS devices is one of the recent trends in sensor technology. However, traditional silicon MEMS have some intrinsic limitations, when applied to the monitoring of high temperature/high humidity processes. Thin ceramic films of alumina, zirconia or LTCC fixed on rigid frame made of the same ceramic material in combination with ink and aerosol jet printing of functional materials (heaters, temperature, pressure, gas sensitive elements) provides a cheap, flexible, and high-performance alternative for silicon MEMS devices used as gas sensors, gas flowmeters, lambda probes, bolometric matrices for automotive and general application.

Pervaporation unit with MEMS gas sensor for the measurement of methane concentration in water

The monitoring of concentration of methane dissolved in water is important for the security of underwater pipelines, delineation of oil and gas fields, and optimization of proper location of oil and gas wells. The reported system consists of metal oxide gas sensor separated from water by hydrophobic pervaporation membrane. Methane MEMS sensor was based on multilayer SiO2/Si3N4 film equipped with platinum heater and coated with sensing layer made of nanoparticle SnO2/Pd (3 wt. %). Methane saturation of water leads to a decrease in sensor resistance by a factor of 6 - 7, the response time of the system is of 200-300 s.