Development of a high flow-rate/high operating frequency Nitinol MEMS valve

This paper presents modeling, fabrication, and testing results for a high flow-rate and high frequency Nitinol MEMS valve. ANSYS (R) is used to evaluate several Nitinol MEMS valve structural designs with the conclusion that a pentagonal flap with five legs produces higher frequencies and higher strengths without the inherent rotation problem present in standard designs. The Nitinol penta-leg design was fabricated using a novel bi-layer lift-off method. A PMGI polymer layer is initially used as an underlayer while a chromium layer is used as a top layer to produce a non-rotational ortho-planar Nitinol MEMS valve array. This array consists of 65 microvalves with dimensions of 1mm in circumference, 50 mu m in leg width, and 8.2 . mu m in Nitinol thickness. Each microvalve covers an orifice of 220 mu m in diameter and 500 mu m in length and is capable of producing a 150 mu m vertical deflection. This Nitinol MEMS valve array was tested for flow-rates in a hydraulic system as a function of applied, pressure with a maximum water flow-rate of 16.44 cc/s.