A magnetostrictive actuator approach based on micromechanical structures is presented. Planar geometries are designed, comprising V-shaped beams and lever transmissions. Several V-shaped beams are stacked in parallel and two of such stacks are placed facing each other. Both are connected to a lever beam. When a magnetic field is applied, the magnetostriction of the active material leads to an elongation/shortening of the V-shaped beams. The lever transmission converts the magnetically induced elastic energy into a reliable in-plane displacement. The overall dimensions of the devices are in the range of 4 mm × 2 mm × 0.4 mm and hence, way smaller compared with state-of-the-art magnetostrictive actuators. For a magnetic flux density of 14 mT, a stroke displacement of 10.2 μm was achieved. With a spring stiffness of 5.56 N/m obtained from simulations, a theoretical area specific work of 72 μJ/m ² was accomplished.

We present a thermal flow sensor designed for measuring air as well as water flow velocities in heating, ventilation, and air conditioning (HVAC) systems. The sensor is designed to integrate the flow along the entire diameter of the pipe also quantifying the volume flow rate of the streaming fluid where the calorimetric principle in constant temperature operation is utilized as a readout method. In the constant temperature mode, a controller keeps a specific excess temperature between sensing elements at a constant level resulting in a flow dependent heater voltage. To achieve cost-effective sensors, the fabrication of the transducer is fully based on printed circuit board technology allowing low-cost mass production with different form factors. In addition, 2D-FEM simulations were carried out in order to predict the sensor characteristic of envisaged setups. The simulation enables a fast and easy way to evaluate the sensor’s behaviour in different fluids. The results of the FEM simulations are compared to measurements in real environments, proving the credibility of the model.

This paper reports a novel construction of a micromachined MEMS magnetometer characterized by static magnetic fields of CERN's reference dipole with a custom made capacitive read-out. The magnetic flux density is characterized via the vibration modes of the MEMS structure, which are sensed capacitively. The device consists of a single-crystal silicon clamped-free plate (cantilever) carrying a thin conductor. The cantilever and the thin film metal electrodes are separated by a small gap, forming a vibrating plate capacitor. Movements of the cantilever are read out conveniently by electronic circuits. A static magnetic field generates a force density acting on the conductor that alternates according to the frequency of the current. When the electrical current is known, the deflection amplitude of the cantilever is a measure of the component of the magnetic flux density that points perpendicular to the current. The highest vibration amplitudes are expected, in the vicinity of resonance frequencies of the micromachined structure. At ambient pressure, the prototype sensor has a measured resonance frequency of 3.8 kHz for the fundamental mode and 20 kHz for the first antisymmetric mode. In experiments, the magnetic flux of the dipole has been characterized between 0.1 and 1 T, with a relative uncertainty of 3 × 10 ^-4 .

Accurate knowledge of the spatial magnetic field distribution is necessary when measuring field gradients. Therefore, a MEMS magnetic field gradiometer is reported, consisting of two identical, but independent laterally oscillating masses on a single chip. The sensor is actuated by Lorentz force and read out by modulation of the light flux passing through stationary and moving arrays of the chip. This optical readout decouples the transducer from the electronic components. Both phase and intensity are recorded which reveals information about the uniformity of the magnetic field. The magnetic flux density is measured simultaneously at two points in space and the field gradient is evaluated locally. The sensor was characterised at ambient pressure by performing frequency and magnitude response measurements with coil and various different permanent magnet arrangements, resulting in a responsivity of 35.67 V/T and detection limit of 3.07 µT/ $\sqrt{\mathrm{Hz}}$ (@ 83 Hz ENBW). The sensor is compact, offers a large dynamic measurement range and can be of low-cost by using conventional MEMS batch fabrication technology.