SBIR Phase I: MEMS Resonant Nanobalance Dew Point Meters

SBIR Phase I:MEMS Resonant Nanobalance Dew Point Meters This Small Business Innovation Research (SBIR) Phase I project aims to develop a micro-electro-mechanical-systems (MEMS) based moisture (dew point) measurement instrument. Measurements of trace moisture are needed in a variety of different industrial sectors, including semiconductor manufacturing, pure gas supply, atmospheric and climate research, aerospace, petrochemical processing, power generation, air filter and purifier manufacturing, and supply of reference standards for other trace gases. Most of the commercially available moisture sensors lack the required accuracy, sensitivity, and responsiveness for many existing applications, or are too costly. The proposed approach utilizes micro-electro-mechanical resonant balances coupled with a cooling element. The instrument will measure dew point using the standard chilled surface technique to deposit a layer of moisture on the surface of the resonant balances. Mass of the deposited moisture causes a shift in the resonant frequency of the micro-resonator that indicates reaching the dew point. Because the nanobalances are capable of weighing as little as a few femto-grams of deposited moisture, only a very small amount of gas needs to be chilled to deposit sufficient water to indicate the dew point. Preliminary prototype assembly and reliability and response time characterizations will be performed in this Phase I effort. The broader impact/commercial potential of this project is development of more accurate, responsive, stable, robust, and versatile moisture measurement instruments than currently available instruments at the same price range. Chilled mirror dew point sensors generally provide higher accuracy compared to other categories of moisture sensors. Such devices however suffer from long response times and vulnerability of their optical sensing mechanism to debris and contamination. The proposed MEMS based technology combines the advantages of the chilled mirror sensors along with faster response and improved robustness provided by the MEMS resonant nanobalances. The reduced chilling needs allow for faster response to changes in moisture content, reduced power consumption for the cooler and novel uses such as battery powered spot sampling systems. An important immediate market for the proposed instrument with great national significance is the measurement of moisture in natural gas. In cold climates excess water in the gas pipeline can freeze the pipe shut, rendering the pipeline useless until the frozen point can be located and cleared. The battery powered, spot checking, robust operation and low cost nature of the proposed instrument will allow widespread use in the upstream Natural Gas pipeline system to measure moisture at points of custody transfer.