Developing novel pollution sensing technologies using precise mass flow control

Developing novel pollution sensing technologies using precise mass flow control

The growth of the IoT (Internet of Things) is driving the need for smaller and more ubiquitous sensors. Normally, one thinks of optical or electrical sensors in this context. This type of measurement has typically been in the province of automotive and process control industries and is largely unavailable at the consumer level.

Presently, IoT is creating a need for low-power, low-cost gas sensors that can be utilized for consumer level applications. There are potential applications in the areas of:

  • Household air-quality monitoring
  • Personalized healthcare
  • Breath analysis
  • A multitude of other applications

However, existing sensors that could be used for these applications are generally not suitable due to large size, high power demands, and high cost.

There are a number of competing technologies focused on providing sensors for this market; one of the most promising sensor types is the field-effect transistor (FET). In a recently published paper, Fahad et. al. describe a novel FET that promises to meet many of the requirements where existing sensors fall short. Many of the experiments described in the paper require highly accurate mass flow of measured gases.1

Challenge: Detecting sulfur/nitrogen dioxide air pollutants

Fahad et. al. demonstrate a novel chemically-sensitive FET capable of detecting sulfur dioxide (H2S) as low as 10 ppb. This invisible gas readily forms toxic compounds such as sulfuric acid and sulfate particles, making it quite dangerous especially to asthmatics. The US has made great strides in reducing sulfur emissions from powerplants. However, in excess of 500 million tons were still produced in 2011 from powerplants and other sources. 2

The same series of experiments showed detection of nitrogen dioxide (NO2) down to 1 ppm levels. This gas is another common air pollutant that can impact personal health. NO2 reacts with other airborne substances to form particulate matter and ozone, both of which have significant negative effects on respiratory health.

The US EPA has recently tightened standards for NO2. These newer standards will require increased monitoring of ambient air levels to ensure compliance. Implementing these new standards will, in turn, require increased training and proper calibration of equipment used to ensure the required accuracy. Alicat makes a range of products specifically designed to help state and local environmental analysts and technicians ensure the needed levels of accuracy.3

Solution: Accurate mass flow control

These experiments demonstrate the efficacy of the novel low-power FET sensor. The experiments were conducted using known gasses from commercial suppliers. Control of the gas input was critical to making accurate assessments of FET function. Alicat mass flow controllers were used to ensure the accuracy of these measurements by precisely regulating the input flow of the gas mixture from 1-100 SCCM.

As scientists and engineers continue to develop novel sensors to enable IoT technologies, precise, reliable mass flow will continue to be required. At Alicat, increasing the pace of scientific innovation is our greatest passion. All of our instruments are custom built to the needs of your science.


1) “Room temperature multiplexed gas sensing using chemical-sensitive 3.5-nm-thin silicon transistors” Fahad HM, Shiraki H, Amani M, Zhang C, Hebbar VS, Gao W, Ota H, Hettick M, Kiriya D, Chen YZ, Chueh YL, Javey A. Science Advances  24 Mar 2017: Vol. 3, no. 3, e1602557 DOI: 10.1126/sciadv.1602557

2) “Sulfur Dioxide Emissions.” Sulfur Dioxide Emissions, US EPA, 2014,

3) “Ambient Air Monitoring.” Alicat Scientific,

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