Chopper-modulated gas chromatography electroantennography enabled using high-temperature MEMS flow control device

• Published in: Microsystems & nanoengineering 2017-12, Vol.3 (1), p.17062-17062, Article 17062
• Main Authors: Zhou, Ming-Da, Akbar, Muhammad, Myrick, Andrew J., Xia, Yiqiu, Khan, Waleed J., Gao, Xiang, Baker, Thomas C., Zheng, Si-Yang
• Format: Article
• Language: English
• Subjects: 639/166/987; 639/638; 639/925/927/511; Access control; Aluminum; Chromatography; Demodulation; Electroantennograms; Engineering; Entomology; Flow control; Gas chromatography; Glass substrates; Low concentrations; Microelectromechanical systems; Organic compounds; Temperature effects; Temperature requirements; Thermodynamic properties; VOCs; Volatile organic compounds
• ISSN: 2055-7434; 2096-1030; 2055-7434
• DOI: 10.1038/micronano.2017.62

We report the design, fabrication and characterization of a microelectromechanical systems (MEMS) flow control device for gas chromatography (GC) with the capability of sustaining high-temperature environments. We further demonstrate the use of this new device in a novel MEMS chopper-modulated gas chromatography-electroantennography (MEMS-GC-EAG) system to identify specific volatile organic compounds (VOCs) at extremely low concentrations. The device integrates four pneumatically actuated microvalves constructed via thermocompression bonding of the polyimide membrane between two glass substrates with microstructures. The overall size of the device is 32 mm×32 mm, and it is packaged in a 50 mm×50 mm aluminum housing that provides access to the fluidic connections and allows thermal control. The characterization reveals that each microvalve in the flow control chip provides an ON to OFF ratio as high as 1000:1. The device can operate reliably for more than 1 million switching cycles at a working temperature of 300 °C. Using the MEMS-GC-EAG system, we demonstrate the successful detection of cis -11-hexadecenal with a concentration as low as 1 pg at a demodulation frequency of 2 Hz by using an antenna harvested from the male Helicoverpa Virescens moth. In addition, 1 μg of a green leafy volatile (GLV) is barely detected using the conventional GC-EAG, while MEMS-GC-EAG can readily detect the same amount of GLV, with an improvement in the signal-to-noise ratio (SNR) of ~22 times. We expect that the flow control device presented in this report will allow researchers to explore new applications and make new discoveries in entomology and other fields that require high-temperature flow control at the microscale. MEMS: Ultrasensitive detection of biologically active compounds A compact and ultrasensitive MEMS device could lead to the identification of biologically active compounds at previously undetectable levels. Gas chromatography electroantennography (GC–EAG) can be used to detect and identify volatile organic compounds, known as odorants, from the electrical response of insect antennae. Conventional GC–EAG, however, suffers from a poor signal-to-noise ratio and is orders of magnitude less sensitive than the insects in detecting odorants, limiting the understanding and potential control of insect behavior. Now, Si-Yang Zheng and colleagues at the Pennsylvania State University, United States, have fabricated an ultrasensitive MEMS device from a polyimide membrane