A piezoelectric microvalve for cryogenic applications

"This paper reports on a normally open piezoelectrically actuated microvalve for high flow modulation at cryogenic temperatures. One application envisioned is to control the flow of a cryogen for distributed cooling with a high degree of temperature stability and a small thermal gradient. The valve consists of a micromachined die fabricated from a silicon-on-insulator wafer, a glass wafer, a commercially available piezoelectric stack actuator and Macor ceramic encapsulation that has overall dimensions of 1 x 1 x 1 cm3. A perimeter augmentation scheme for the valve seat has been implemented to provide high flow modulation. In tests performed at room temperature the flow was modulated from 980 mL min[?]1 with the valve fully open (0 V), to 0 mL min[?]1 with a 60 V actuation voltage, at an inlet gauge pressure of 55 kPa. This range is orders of magnitude higher flow than the modulation capability of similarly sized piezoelectric microvalves. At the cryogenic temperature of 80 K, the valve successfully modulated gas flow from 350 mL min[?]1 down to 20 mL min[?]1 with an inlet pressure of 104 kPa higher than the atmosphere. The operation of this valve has been validated at elevated temperatures as well, up to 380 K. The valve has a response time of less than 1 ms and has operational bandwidth up to 820 kHz."http://deepblue.lib.umich.edu/bitstream/2027.42/64193/1/jmm8_1_015023.pd