Microvalves for Natural-Gas Analysis With Poly Ether Ether Ketone Membranes

Abstract

We present the use of poly ether ether ketone (PEEK) as a membrane material for a new type of gas microvalve, which is suitable for the harsh environments of natural gas. The design, fabrication, and experimental characterization of the PEEK-based microvalves are presented first, revealing leakage levels of less than 230 nL · min −1 under nitrogen and helium. Then, the main mechanical properties of the PEEK membranes are derived from both static and dynamic measurements, leading to a Young's modulus of 3.1 GPa and an inplane anisotropic stress field, with both tensile and compressive components in two perpendicular directions and whose magnitudes are +33.9 MPa and −6.8 MPa, respectively. A blister test gave an adhesion energy estimated between 61 and 158 J · m −2 . Finally, temperature cycles have been conducted on the microvalve, showing a resistance of up to 300 • C, together with an improved closing of the membrane. [2010-0062] Index Terms-Membrane, micro-gas chromatography, microvalves, poly ether ether ketone (PEEK).

MEMS Devices for Miniaturized Gas Chromatography

“…The six valves opened and closed by changing the pressure through their actuation holes. In sampling mode, valves A, D, and E are closed, while for injecting samples onto separation channels, valves B, C, and F are closed (Figure 1) [5,6]. Moreover, a customized volume injector (0.5-15 μL) was designed by Holland et al [7].…”

Low-leakage gas sample-injection system for gas chromatography in harsh environments

“…1). The microvalves are pneumatically actuated; their detailed structure was presented in our previous report [5]. The main structural feature is the use of polyetheretherketone (PEEK) as the constitutive material of the membrane.…”

“…The centers of the six white circles are the locations of the tiny entry and exit holes (20 µm in diameter). The microvalves [5] close (open), after contact (release) of the membrane onto (from) the valve seat, respectively, depending on the corresponding actuation pressure applied on each valve for individual control. …”

“…On the top side of wafer 3, there are channels connecting the pneumatic actuation holes to form two actuation ports on wafer 4, for the two groups of microvalves that require simultaneous actuation: group A, D, and E and group B, C, and F. After the four wafers have been micromachined, wafers 1 and 2 are bonded using a silicon-silicon bonding process; similar bonding is performed for assembling wafer 3 and wafer 4. Finally, the stack {wafers 1 and 2} / PEEK / {wafers 3 and 4} is finalized with a thermocompression bonding process [5]. It is worth mentioning that wafer 4 is optional, since its function is only for organizing the six valves into two groups.…”

“…Motivated by the specific needs imposed by the harsh environment of natural gas, our group recently presented [5] the integration of PEEK membranes into silicon stacks, together with an experimental study of gas microvalves based on such membranes. These microvalves appeared highly performing in terms of low leakage (<4 nL/s), with excellent thermal and chemical potential, since they could withstand temperatures up to 300°C, as well as corrosive chemicals such as hydrogen sulfide (H 2 S).…”