Two-Dimensional Micromachined Flow Sensor Array for Fluid Mechanics Studies

Abstract

We discuss two types of micromachined flow sensors realized by using novel microfabrication processes—a hot-wire anemometer (based on thermal transfer) and a biologically inspired flow sensor (based on momentum transfer). Both sensors are enabled by a new, efficient three-dimensional assembly technique called the plastic deformation magnetic assembly method. The sensors can be packaged in high-density, two-dimensional arrays efficiently, with each sensor node capable of performing two-component or three-component flow sensing. We first discuss the development of new hot-wire anemometers (HWA). The HWA uses a thermal element (hot wire) that is made of Pt/Ni/Pt film with a measured temperature coefficient of resistance of 2,700 ppm/°C. The thermal element is elevated out of plane by using support beams made of polyimide, a polymer material. Both steady-state and transient characteristics of the sensor have been experimentally obtained. The second type of flow sensor is based on momentum transfer principles and inspired by fish lateral line sensors. Each sensor consists of a vertical cilium attached to a horizontal cantilever. Fluid flow imparts moment on the vertical cilium, and causes the horizontal cantilever to bend. The fabrication process and preliminary measurement data are presented.