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Image from Joe Green, Canadian Beaver Engineering Center
New York, USA Scientists Successfully Develop New Chip-based Methane Spectrometer
[China Instrument Network Instrument Development] The process of extracting natural gas from the earth and transporting it through pipelines releases methane into the atmosphere. Methane, the main component of natural gas, is a greenhouse gas. Its impact on global warming is about 25 times that of carbon dioxide, which makes it very effective in trapping atmospheric heat. A new chip-based methane spectrometer, which is smaller than a dime, may one day be able to monitor large areas of methane leakage more efficiently and easily.
Scientists from the IBM Thomas J. Watson Research Center in Yorktown, New York, have developed a new type of methane spectrometer that is smaller and more economical to manufacture than today's standard spectrometers. In the Optical Society's high impact factor magazine “Opticaâ€, the researchers introduced the new spectrometer in detail and showed that it can detect methane gas at concentrations as low as one in 10,000.
Only a small amount of maintenance, with high impact resistance
This spectrometer is based on silicon photonics technology, which means that it is an optical device made of silicon, that is, a material used to make a computer chip. Since this chip-based methane spectrometer can be manufactured using the same high-volume processing methods as computer chips, the spectrometer, along with the housing and battery or solar power supply, can cost as little as several hundred dollars if mass-produced.
William Green, head of IBM's research team, said: "Compared to the cost of tens of thousands of methane detection optical sensors available on the market today, high-volume processing can give chip spectrometers a more important value proposition." There are also no basic requirements for precise temperature control of the moving parts. This type of sensor can be operated for many years with little maintenance.â€
This cost-effective and robust spectrometer can bring exciting new applications. For example, the IBM team is working with a partner in the oil and gas industry to develop a project that will use spectrometers to detect methane leaks, avoid the on-site search and repair of thousands of leak sites, and save the company time and money .
“In the course of natural gas extraction and distribution, when the equipment in the well fails, the valve jams or there is a crack in the pipeline, methane may leak into the air. “We are studying a method that can use this chip spectrometer to distribute on the wellhead. Sensor network method. For example, the data collected by these sensors will be processed using IBM's physical analysis software, which automatically determines the location of the leak and the volume of the leak. â€
Methane is a trace gas, which accounts for less than 1% of the Earth's atmospheric volume. Although researchers have demonstrated methane detection, the same method can be used to detect the presence of other individual trace gases. It can also be used for multiple gas detections at the same time.
"Our long-term vision is to incorporate these types of sensors into household things such as cell phones or vehicles that people use every day. These sensors can be used to detect pollution, dangerous levels of carbon monoxide, or other molecules of interest." Team member Eric Zhang said. "Because this spectrometer provides a platform for multi-species detection, one day it may also be used for respiratory analysis for health monitoring."
Reduce the spectrometer
The new device uses a method called absorption spectroscopy, which requires the laser to be at the wavelength of the only absorption of the molecule being measured. In a traditional absorption spectrum setup, the laser passes through air or free space until it reaches the detector. Detecting the light reaching the detector can give us an idea of ​​the amount of molecules of interest in the air that are absorbed, and at the same time calculate their current concentration.
The new system uses a similar method, but it is not a free space device. Instead, it passes the laser light through a narrow silicon waveguide, which is a 10-cm-long serpentine pattern above the chip that can measure the 16-square millimeter range. Some light is trapped inside the waveguide, and about 25% of the light extends to the outside of the silicon into the air, where it can interact with trace gas molecules passing near the sensor waveguide. The researchers used a near-infrared laser (1650 nm wavelength) for methane detection.
In order to increase the sensitivity of the equipment, the researchers carefully measured and controlled the factors that caused the noise and the false absorption signal, fine-tuned the design of the spectrometer, and determined the geometric parameters of the waveguide to produce satisfactory results.
Side by side comparison
To compare the performance of the new spectrometer with the performance of a standard free-space spectrometer, they placed the device in an environmental chamber to release and control the concentration of methane. Researchers have found that chip-based spectrometers are more accurate than equivalent-level free-space sensors, and they reduce the amount of light that interacts with air by 75% compared to free-space designs. In addition, the sensitivity of the chip sensor is quantified by the minimum discernible range of methane concentration and shows superior performance over other laboratory-developed free-space spectrometers.
"Although silicon photonics systems - especially those that use refractive index changes - have been previously explored, the innovative part of our work is to use this type of system to detect very weakly absorbed signals at low concentrations of methane, and Comprehensive analysis of our sensor chip noise and minimum detection threshold."
The current version of the spectrometer requires light to enter and exit the chip through the fiber. However, researchers are trying to incorporate light sources and detectors on the chip, which will create an essentially electrical device that does not require fiber optic connections. Unlike current free-space sensors, this chip type does not require special samples or optical preparations. Next year, they plan to conduct field tests by placing spectrometers in larger networks, including other off-the-shelf sensors.
“Our work shows that all the knowledge behind silicon photonics manufacturing, packaging and component design can be brought into the field of optical sensors, completing high-volume, in principle, low-cost sensor processing, and ultimately enabling new applications of this technology.†Green said.
(Original Title: Microchip Based Methane Spectrometer Helps Reduce Greenhouse Gas Emissions)