AVS 51st International Symposium
    MEMS and NEMS Monday Sessions
       Session MN-MoP

Paper MN-MoP11
Determination of Young's Modulus for Silicon Membrane in Cryogenic Micropump using Laser Michaelson Interferometry

Monday, November 15, 2004, 5:00 pm, Room Exhibit Hall B

Session: Poster Session
Presenter: Y. Zhao, Boston University
Authors: Y. Zhao, Boston University
B. Li, Boston University
X. Zhang, Boston University
Correspondent: Click to Email
In micro satellites, lots of dedicate instrumentations were compacted in a limited room for demonstration of new concepts. The ambient temperature would rise if heat generated could not be well dissipated, which will ruin many heat sensitive devices, such like infrared camera. As a solution, a two phase loop using micro pump was used to keep a narrow cryogenic range. This micropump depends on elastic deformation of silicon membrane to transfer cryogen. The mechanical properties of the membrane, especially elastic modulus, are thus critical in heat balance analysis. However, conventional tensile experiment was not practicable for non bulk material and in cryogenic environment. In this paper, we report the work using laser Michaelson interferometer for Young's modulus measurement of thin membrane in cryogenic environment. Square membranes were fabricated on SOI wafers. The membrane deflection was achieved using laser Michaelson interferometer. Actuating with differential pressure of compressive gas, the dependency of deflection upon temperature was achieved. Given the actuating pressure and membrane geometry, Young's modulus of the membrane was consequently obtained. It was found Young's modulus increases with decreasing temperature, indicating a much stiffer material in cryogenic environment. A calibration was further carried out utilizing longitudinal wave propagating along the membrane thickness. The membrane was locally vibrated using 1064 nm Nd:YAG laser. The generated longitudinal wave was examined at the same point by laser Michaelson interferometer. Young's modulus derived from the propagating velocity corresponds with previous deflection measurement. It provides a feasible way to determine membrane stiffness in cryogenic environment, which is not limited to single material membrane, but also good for any composite membranes, like silicon membrane deposited with oxide film, which is not readily practicable using other current approaches.