Evaluation of Design and Performance of a Cryogenic Mems Micropump Realized with Si-Based Diaphragm Using Combination of
- PDF / 328,334 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 46 Downloads / 160 Views
A5.52.1
EVALUATION OF DESIGN AND PERFORMANCE OF A CRYOGENIC MEMS MICROPUMP REALIZED WITH SI-BASED DIAPHRAGM USING COMBINATION OF ZYGO/WYKO INTERFEROMETER AND RAMAN SPECTROSCOPY Yi Zhao, Daryl Ludlow, Biao Li, Xin Zhang Department of Manufacturing Engineering and Fraunhofer USA Center for Manufacturing Innovation, Boston University, Boston, MA 02215, USA ABSTRACT This paper reports work concerning a silicon-based micro pump for use in a cryogenic cooling system. The diaphragm deflection, which is critical for the control of pumping capacity, was accurately derived using a combination of ZYGO and WYKO interferometer. The relationship between the pumping capacity and differential pressure was further achieved. Stress distribution was obtained using Micro Raman spectroscopy. It was found that Young’s modulus derived from the maximum deflection increases with decreasing temperature. The compressive stress concentrates at the edge centers; whereas the tensile stress occurs at the diaphragm center. There is a fairly good match between the theoretical predications and experimental observations. INTRODUCTION Heat sensitive instruments used in satellite application need to be cooled down at a low temperature for better efficiency. An active cooling system is desired rather than gas flow over devices or passive atmospheric heat exchangers, in order to keep the instruments within a narrow acceptable operation temperature range [1, 2]. Furthermore, as many instruments need to move and/or rotate smoothly without any restrictions, the cooling system should give as many degrees of freedom as possible to the instrument, i.e., a remote cooling system is required. We are building an active cooling system based on silicon micro pumps [2]. The micro pump array was placed in a closed loop to transfer the cryogen (liquid nitrogen or liquid oxygen) at specific pumping rate. The cryogen absorbs heat dissipated from the evaporator (instrument to be cooled down) and gives it off to the condenser (contacting with cryocooler) so as to keep the instrument at low temperature. A long flexible tubing coil was applied between the micro pumps and the evaporator so that the flexibility of the instrument was ensured. MEMS-sized micro pumps usually consist of multiple layers of silicon [3, 4]. One major concern of micro pump design is the pumping capacity (volume stroke); an appropriate pumping capacity is required to keep the heat balance of the instrument. The other concern lies in the diaphragm failure. To transfer cryogen, large volume stroke is preferred. However, larger volume stroke will induce higher stress within the diaphragm. For this reason, the maximum deflection should not be exceeded to avoid failure of the silicon diaphragm. Given the importance of both issues, this paper reports design and performance evaluation of silicon diaphragm during working operation. EXPERIMENTAL STUDIES Diaphragm characterization The square diaphragm was fabricated on 4 inch, (100) single crystal silicon wafers by standard etching process using potassium hydro
Data Loading...
