A micromachined silicon valve driven by a miniature bi-stable electro-magnetic actuator

In this paper a novel combination of a micromachined silicon valve with low dead volume and a bi-stable electromagnetic actuator produced by conventional machining is presented. The silicon valve part, 7×7×1 mm3 in dimensions, is a sandwich construction of two KOH etched silicon wafers with a layer of chemical resistant silicone rubber bonded in between. This middle layer provides the flexibility needed to move the valve boss positioned in the top wafer during valve operation, but also results in improved sealing if the valve is closed. In order to drive the valve, a dedicated bi-stable electromagnetic actuator has been designed by applying a finite element software package. The resulting actuator consists of a spring-biased armature that can move 0.2 mm up and down in a magnetically soft iron housing, incorporating a permanent magnet and a coil. This large stroke makes the valve particle tolerant. A major advantage of the bi-stable design is that only electrical energy is needed to switch the valve between the open and closed state. The actuator has been manufactured by conventional machining and was attached to the individual silicon valve parts resulting in a valve with a footprint of 7×7 mm2 and a height of 21 mm. The valve showed an open/closed ratio of more than 100 at 0.1 bar

The Wheatstone Gadget : a simple ciruit for the measuring differential resistance variations

This paper presents a simple circuit for measuring differential resistance variations. The Wheatstone Gadget, or The Gadget, is able to measure the same parameters as the Wheatstone Bridge in combination with an emitter-coupled pair [1], but with fewer components and fewer supply voltages. The Gadget is a simple circuit with a lot of possibilities, as shown in this paper. It needs only one power supply and is especially designed for small resistor values, which makes it well suitable for micromechanical applications

Regulatory roles of androgens in cutaneous wound healing

An acoustic wave consists of two elements, the acoustic pressure and the acoustic flow. Up to now one has to measure the pressure and calculate the flow to determine the acoustic flow, so it would be convenient to have a sensor that is able to measure acoustic flows. At the University of Twente a novel device has been developed which fulfils this need. In this paper a short introduction to the governing principles of this dynamic flow sensor, the fabrication process, the electronics and some of its interesting applications will be presented. This micromachined device measuring acoustic flows is called the microflown or μ-flown

The μ-flown: Novel device measuring acoustical flows

An acoustical wave consists of two elements, the acoustic pressure and the acoustic flow. Till now to determine the acoustic flow one has had, to measure the pressure and calculate the flow. So it would be convenient to have a sensor which is able to measure acoustical flows. At the University of Twente a novel device has been developed which fulfils this need. In this paper a short introduction to the governing principles of this dynamic flow sensor and some of its interesting applications will be presented. This micromachined device is called the microflown