Niklas Svedin

A new silicon gas-flow sensor based on lift force

This paper presents the first silicon-flow sensor based on lift force. The sensor is a bulk-micromachined airfoil structure that uses the lift force as a sensing principle. The lift force acts normal to the flow in contrast to drag-force sensor types, where the force acts in the flow direction. The sensor utilizes the special distribution of the lift force along the length of the sensor structure. Since the sensor, like an airfoil, is mounted at a small angle to the flow, it induces very little flow disturbance. The sensor consists of two plates connected to a center beam. Each plate is 5/spl times/5-mm square with a thickness of 30 /spl mu/m. The flow-induced forces deflect the two plates in the same direction, but with different magnitude. The deflections are detected by polysilicon strain gauges. The differential mode bridge makes the sensor insensitive to common mode deflection, e.g., acceleration forces. The lift-force principle is characterized using fundamental airfoil theory. The sensor has been experimentally verified, and a flow sensitivity of 7.4 /spl mu/V/V/(m/s)/sup 2/ has been measured in both flow directions.

A lift-force flow sensor designed for acceleration insensitivity

Abstract A silicon gas-flow sensor based on lift force is described. The sensing structure is made of two equal plates arranged to be deflected by the lift force. The deflection is detected with polysilicon piezoresistors connected in a Wheatstone bridge configuration. Due to its symmetric design, the sensor suppresses artifacts caused by acceleration forces. Here this ability is verified both theoretically and experimentally. A flow sensitivity of 0.054 μV/V/(1/min) 2 has been measured. Due to the lift-force sensor design, the sensitivity is independent of the flow direction and the induced pressure drop is relatively low. The pressure drop and the flow sensitivity normalized to the pressure drop have been studied as functions of the flow attack angle.

A static turbine flow meter with a micromachined silicon torque sensor

A new class of flow sensors is introduced where a static turbine converts the volume flow into a torque. In contrast to conventional turbine meters, the wheel does not rotate and consequently it is not sensitive to bearing friction and wear that a rotating wheel experiences. The sensor performance has been evaluated for different blade lengths and blade angles and a model is given to predict the influence of these parameters. Optimization of the wheel can be done in terms of maximizing the sensitivity/pressure-loss ratio. The most efficient wheel in this analysis has a blade length of 2.7 mm and a blade angle of 30/spl deg/ giving a sensitivity of 4.0 /spl mu/V/V/(1/min) when measured using a new silicon torque sensor design.

Design and Fabrication of Addressable Microfluidic Energy Storage MEMS Device

Design and fabrication of microfluidic energy storage devices that are based on the control of the liquid electrolyte inside a power cell are presented. A 12-cell array of individually addressable reserve microbatteries has been built and tested, yielding ~ 10-mAh capacity per each cell in the array. Lithium and manganese dioxide or carbon monofluoride (Li/MnO2 and Li/CFx) have been used as anode and cathode in the battery with LiClO4 -based electrolyte. Inherent power management capabilities allow for sequential single cell activation based on the external electronic trigger. The design is based on the superlyophobic porous membrane that keeps liquid electrolyte away from the solid electrode materials. When power is needed, battery activation (a single cell or several cells at once) is accomplished via electrowetting trigger that promotes electrolyte permeation through the porous membrane and wetting of the electrode stack, which combines the chemistry together to release stored electrochemical energy. The membrane and associated package elements are prepared using microelectromechanical system fabrication methods that are described in details along with the assembly methods.

A new bi-directional gas-flow sensor based on lift force

A new bi-directional silicon gas-flow sensor based on lift force has been designed and tested. The lift force deflects an airfoil structure and the deflection is detected by four piezoresistive strain gauges. The lift force principle is based on fundamental airfoil theory and has been verified both electrically and optically. A flow sensitivity of 7.4 /spl mu/V/V/(m/s)/sup 2/ has been measured in both flow directions.