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We propose a flexible proximity sensor to detect sub-centimeter distance with an ultra-high displacement resolution. The proximity sensor is realized by integrating a semi-transparent organic photo detector with a transparent top electrode and a finger-type bottom electrode. By placing the semi-transparent finger-type photodetector on a light source, such as a light-emitting diode (LED), the photodetector can detect the light reflected from an object on top of the sensor. With the highly compact structure, the detecting range is from 1 mm to 30 mm. From 1 mm to 10 mm, the sensor is particularly sensitive and delivers a resolution of 1 mm. The air-stable photodetector can also be fabricated on a flexible substrate without encapsulation, enabling the integration with arbitrary light sources. After 1000 times bending, the flexible photodetector shows no obvious degradation.

This paper reports a MEMS gradiometer consisting of two independent, laterally oscillating masses on a single chip with integrated optical readout featuring a responsitivity of 35V/T at resonant operation. The symmetrical design of the two masses offers high accuracy and low cost by using conventional MEMS batch fabrication technology. The sensing principle is based on lateral displacement of the masses actuated by Lorentz forces which modulates a light flux passing through a stationary mask and the moving mask integrated in the masses. Phase and intensity detected by photodiodes reveal information about the uniformity of an external applied magnetic field, hence, enables the measurement of gradient-, homogeneous- and offset gradient magnetic fields.

We present a displacement-sensitive sensor comprising a microelectromechanical (MEMS) chip and organic optoelectronic components capable of measuring the heart and respiration rate on humans. The MEMS sensor relies on the inertial deflection of a small silicon oscillator. The readout of the deflection is optical and works via modulation of the light flux passing through the MEMS. Organic optoelectronics are used as light source and detector, since these offer a homogeneous light distribution and a more compact package in a future integration. Two types of MEMS, differing in their resonance frequency, were designed and characterised in combination with both organic and inorganic optoelectronics prior to measuring heart and respiration rate. Subsequently, by measurements on the neck, pulse and respiration rate were successfully measured.

Depending on the geometry, microstructures oscillating laterally in air are mainly damped by Couette-type flow or shear waves emitted into the surrounding. Models for these types of damping imply a flat, closed, laterally moving plate. Due to fabrication or readout, such MEMS/MOEMS often feature holes in the plate. Therefore, the requirement of a perfect surface is certainly not fulfilled. We present measurements that show how these holes influence the damping of laterally oscillating MOEMS. In two series of test structures, both the size and the number of the holes are varied investigating the respective differences in the damping.

This contribution describes an opto-mechanical transducer with a non-linear transfer behaviour and its impact on the quantification of static and dynamic displacements in a vibrating measurement mode. The device's output signal is proportional to a lightflux that is modulated by two overlapping gratings. One of the gratings is deposited on a fixed glass cover while the other one is etched into a moveable seismic mass of a Si MEMS chip. The non-linear transfer characteristic is achieved by paring a triangular grating with a rectangular one. The mass is actuated by a mechanical shaker unit and the resulting 1 st and 2 nd harmonic of the output signal are recorded with Lock-In amplifiers. These harmonics contain information about the static displacement and the vibration amplitude of the mass. The presented method allows for a precise measerement of the static displacement with an error of ±0.017% compared to DC measurements exhibiting an error of ±0.066%.

We report on an accurate analytical model for the squeeze-film damping in laterally oscillating MEMS and MOEMS, which has not been available up to now. The models currently used are not able to correctly predict the damping and underestimate the squeeze- film contribution by a quite large factor of ∼4. This discrepancy was overcome by choosing more appropriate boundary conditions for solving Reynold's lubrication equation which governs the behavior of thin fluid films. The model was tested against numerical FVM computations with the open source software package OpenFOAM as well as measurements of MOEMS test devices with varying width of the squeeze-film gap and is in good agreement with both. This can now be used to increase the efficiency in thedesign step not only of laterally moving microstructures.

This contribution describes a novel magnetic field transducer based on a MOEMS (micro-opto-electo-mechanical-system) readout. The silicon structure is deflected in a static magnetic field due to the Lorentz force This deflection is measured with the mechano-optical transducer [1] . The transduction method is based on the modulation of a perpendicularly introduced light flux. The modulation is achieved by one movable optical grating on a suspended structure and a second grating that is fixed to the foundation of the system. The proof-of-concept device was characterized at ambient pressure exhibiting a sensitivity of 200 mV/T. The noise equivalent magnetic resolution limit is 1.5 μT/√Hz which results mainly from the opto-electrical evaluation circuit. By introducing advanced opto-electronics and using improved MEMS devices it is feasible to reduce this value down to 1 nT/√Hz which is equivalent to the fundamental mechanical Brownian noise limit.

In the past years, researches demonstrated the great potential of novel MOEMS vibration sensors regarding their displacement resolution and sensitivity. The authors show that it is possible to further enhance the dynamic range of these sensors. This is achieved by utilizing feedback mechanisms such as electrostatic actuation without any crosstalk to the optical readout. Furthermore, this allows for canceling out unwanted ringing. The discussed proof of concept prototypes incorporate two electrostatic comb-drive actuators. They enable the seismic mass to reset along the main oscillation axes over a path of several microns and up to the resonance frequency of 400 Hz. It was proven that there is no unwanted crosstalk between the actuation and the position readout. The MOEMS readout features a sensitivity of approximately 200 mV/μm with a noise equivalent displacement of 35 pm/√Hz.

We present a first proof of principle of applying organic semiconductors as key components in micro-mechanical vibration sensors. The mechanical part of the MOEMS sensor readout is etched into the device layer of an SOI chip and consists of a laterally deflecting inertial mass that features a two-dimensional grid of rectangular holes. An identical grid is evaporated onto a glass chip bonded onto the silicon chip in such way that any deflection of the seismic mass will modulate the light flux passing through the device. The light flux is provided in this case by an OLED and detected by an OPD. It is shown with a proof of concept device that for such sensors organic optoelectronics can replace inorganic ones, which is the starting point for developing a variety of MOEMS sensors based on printed optoelectronic devices.

A passive thermal micro-actuator with large area specific work and large displacement, fabricated of electroplated nickel on a silicon substrate is presented. The actuation relies on the thermal expansion of beams in a V-shaped geometry. Two V-shaped beam stacks are aligned opposite to each other and are coupled to a lever transmission. The actuator exhibits low energy losses due to the deformation of the structure and can efficiently convert the thermally induced elastic energy into mechanical work. An analytical model considers these thermally induced mechanical energies and the energy losses caused by the deformation of the material. The calculated deflections are compared with the measured ones and results of finite-element method simulations. The presented actuator operates completely passive, relies only on temperature changes of the surrounding environment, and exhibits a measured temperature-dependent linear deflection coefficient of $1.48~\mu \text{m}$ /K with a simulated blocking force of $57~\mu \text{N}$ /K. The structure occupies an area of $2135 \,\, \times \,\, 1831~\mu \text{m}^{2}$ and the area specific work is calculated to be $21.7~\mu \text{J}/\text{K}^{2}/\text{m}^{2}\vphantom {\sum ^{R^{R}}}$ , beating state of the art thermal actuators. As proof-of-concept, a passive micro-electro-mechanical systems temperature threshold sensor is fabricated, featuring the actuator and a bistable beam that switches between two stable positions when a specific threshold temperature is exceeded. [2014-0317]

This paper reports a novel 3D printed MEMS magnetometer with optical readout, which demonstrates the advantages of 3D printing technology in terms of rapid prototyping. Low-cost and fast product development cycles favour 3D printing as an effective tool. Sensitivity measurement with such devices indicate high accuracy and good structural performance, considering material and technological uncertainties. This paper is focusing on the novelty of the rapid, 3D-printing prototyping approach and verification of the working principle for printed MEMS magnetometers.

This paper reports a novel 3D-printed MEMS resonant magnetometer with optical readout which features a mechanical conversion of a vertical oscillation into a horizontal one. This demonstrates the advantages of 3D-printing technology in terms of rapid prototyping, low costs and fast product development cycles. In addition, 3D-printing enables ‘true’ three-dimensional MEMS structures in contrast to the traditional MEMS technology which allows only two dimensional structures. The measurement approach comprises a hybrid implementation of an optical modulator, an LED and a photodetector.

This paper reports on a novel, miniaturized magnetomechanical transducer/sensor made of borosilicate glass with wide dynamic range. The prototype is manufactured with laser micromachining and ablation techniques. Compared to state of the art, borosilicate glass substrate offers the highest thermal shock resistance and is best suited for MEMS magnetometers, for aerospace and space applications or magnetic monitoring systems for diagnostics and plasma stability control of nuclear fusion experiments, where thermal shock resistance is a critical requirement.

We report on a new optical sensing principle for measuring the electric field strength based on MEMS technology. This method allows for distortion-free and point-like measurements with high stability regarding temperature. The main focus of this paper rests on an enhanced measurement set-up and the thereby obtained measurement results. These results reveal an improved resolution limit and point to the limitations of the current characterization approach. A resolution limit of 222 V/m was achieved while a further improvement of roughly one order of magnitude is feasible.

This paper reports on a MEMS gradiometer consisting of two independent laterally oscillating masses on a single chip with integrated optical readout. The symmetrical design of the two masses offers high accuracy and low cost by using conventional MEMS batch fabrication technology. The sensing principle is based on laterally displacement of the masses actuated by Lorentz forces which modulates a light flux passing through a stationary mask and the moving mask integrated in the masses. Phase and intensity detected by photodiodes reveals information about the uniformity of an external applied magnetic field, hence, enables the measurement of gradient-, homogeneous-and offset zradient maanetic fields. A quadrupol magnetic field created from four identical neodymium bar magnets had been characterised to demonstrate the sensor's working principle.

High performance applications such as the detection of seismic activity or structural health monitoring require sensors with low resonance frequencies. For micro-electro-mechanical-system (MEMS) accelero-meters and vibration sensors it is crucial to lower the resonance frequency in order to increase its sensitivity or bandwidth. In contrast to commercial devices which exhibit resonance frequencies of more than 500 Hz, we present extremely sensitive, optically read-out devices with resonances down to 45 Hz. This low resonance frequency was mainly achieved by fabricating the complete seismic mass from one single crystal silicon block. Compared to previously reported work the resonance frequency could be lowered from over 940 Hz down to 45 Hz while the resolution was massively increased from 7.6 μg/sqrt(Hz) to 1.17 μg/sqrt(Hz) (@4 Hz).

The majority of MEMS vibration sensors requires relatively high resonance frequencies of several kilohertz to avoid mechanical contact of moving parts such as electrode plates. In contrast to that, our hybrid micro-opto-electro- mechanical system (MOEMS) enables sensor applications at low frequencies. This work describes a distinct MOEMS featuring extremely low resonance frequencies of below 200 Hz. It is operated ambient air without closed loop feed- back, extensive electronics and cooling. Due to the soft suspension of the micro-mechanical sub-system the funda- mental limit, the Brownian noise floor, is reached. The resulting noise equivalent displacement for frequencies above the resonance is 1.9 pm/ √Hz, which is equivalent to 0.29 μg/ √Hz below the resonance. We describe the design space for sensors with further enhanced sensitivity and resonance frequencies far below 100 Hz.

We report on design rules for the passive air damping of laterally oscillating MOEMS [1]. They allow for a tailor made charac- teristic of the transfer function of a microsensor for a given field of application. Measurements in air at atmospheric pressure as well as in vacuum at a pressure of 10−4 to 10−1 mbar were accompanied by finite volume method computational fluid mechanics simulations using the open source software OpenFOAM®. These were combined with analytic models to identify and quantify the important parameters of the air damping of a micromachined vibration sensor with optical read-out. Our results prove that the desired damping can be achieved with high precision. This important fact can now be used to design a wide range of MOEMS with a well-defined quality factor Q, e.g. for resonant sensing (high Q, low frequency range) or vibration sensing (low Q, high frequency range).

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 &micro, T/ 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.

This paper presents a magnetic field sensor with capacitive read-out, whose active element is a micromachined mechanical resonator. The MEMS magnetic field sensor exploits the Lorentz force to detect external magnetic flux density through the displacement of the resonant structure, which can be measured with optical and capacitive sensing techniques. The micromachined U-shaped cantilever features a length of 2 mm, a base width of 90 μm and a thickness of 20 μm, and is manufactured in SOI technology. The designed sensor has a measured resonant frequency of 4.359 kHz for the fundamental mode and a calculated mass of the flexible structure of 24.5 ng. A quality factor in the order of 104 at an ambient pressure of 0.3 Pa has been measured where a magnetic field resolution of 15 nT can be achieved. Although these arrangements are well suited to capacitively sense the vibrations caused by the Lorentz force on the current lead on the silicon part, care has to be taken to avoid undesired mutual interferences. A serious interference was observed in case of a DC bias voltage at the readout capacitance and a significant voltage drop caused by the current needed for the generation of the Lorentz force. This work investigates in detail this phenomenon as well as the complete physical transduction chain and improves the understanding of such microelectromechanical systems significantly. An analytical model of the electrostatic system is established including all relevant components and their interactions as well as the motion of the MEMS part. The importance of electrostatic back-action for a feasible detection limit for magnetic fields was recognized for the first time.

The thermal actuator presented in this paper consists of two symmetrically V-shaped beam stacks, where each stack consists of six beams in parallel. The stacks are coupled facing each other and slightly shifted along the mirror axis. Both stacks are connected to a lever beam and fixed at four anchor regions to the substrate. Due to the difference in the coefficient of thermal expansion of the material of the beams and the one of the substrate, the tip of the lever moves perpendicular to the mirror axis. The device is fabricated from galvanic deposited nickel on a silicon substrate. Finite element simulations were carried out to optimize the design with respect to the sensitivity and the maximum mechanical stress. The stress needs to be lower than the yield strength of the material. Otherwise, plastic deformations of the beams would lead to irreversible deflections of the beam tip. This limits the overall sensitivity of the design. First results of the device with 400 μm long bent beams show a linear behavior and a sensitivity of 0.5 μm/K and forces of 66 μN/K for a temperature range of ź30 °C up to +40 °C.

This paper presents a design guideline for matching a fully implantable middle ear microphone with the physiology of human hearing. The guideline defines the first natural frequency of a seismic sensor placed at the tip of the manubrium mallei with respect to the frequency-dependence hearing of the human ear as well as the deflection of the ossicular chain. A transducer designed in compliance with the guideline presented reduces the range of the output signal while preserving all information obtained by the ossicular chain. On top of a output signal compression, static deflections, which can mask the tiny motions of the ossicles, are reduced. For guideline verification, a microelectromechanical system (MEMS) based on silicon on insulator technology was produced and tested. This prototype is capable of resolving 0.4 pm/Hz with a custom made read-out circuit. For a bandwidth of 0.1 kHz, this deflection is comparable with the lower threshold of speech (≈ 40 phon).

For vibration and displacement sensors, robustness is one of the key requirements. Optical measurement concepts are among the most promising possibilities to achieve it. The presented microoptoelectromechanical system sensor modulates a light flux by means of two congruently placed aperture gratings: one etched into a seismic mass and the other fixed to the sensor package. Commercially available LED and photodetector components at the top and bottom of the sandwich structure generate and detect this modulated light flux and allow for a cost-effective implementation. The prototype used for experimental verification is actuated by inertial forces and exhibits a high sensitivity of 0.85 mV/nm for displacements of the seismic mass and a corresponding noise level of about 14 pm/√Hz. This sensitivity and noise level can be further improved, paving the way for small, lightweight, robust, and high-precision displacement sensors for a large variety of applications.

Proximity sensors are interesting devices for applications like smart homes or human-machine interfaces. This work investigates a cheap and compact short-range proximity sensor based on an organic photo detector combined with a commercial LED. Low-cost solution-processed organic materials are used, and low process temperatures at 140 °C also facilitate future integration on, e.g., plastic substrates. In particular, to avoid damage of the organic layer during the patterning process, a new organic photo detector with a semitransparent organic active layer and a transparent silver nanowire top electrode was designed. The proposed sensor can be realized by using only one shadow mask to pattern the opaque bottom electrode layer. The opaque finger-type bottom electrode not only partly shields the light emitted from below the device, but also defines the active regions with vertical electric field to generate and collect photo current. In the experiments conducted in this paper, the maximum detection distance was found to be 2 cm, whereas the lower end of the measurement range was 0.2 cm.

This paper presents encouraging results of a novel optoelectronic conversion method for relative displacement. An optical modulator responding to acceleration and gravitation is used for characterization. The Si microelectromechanical system (MEMS) component comprise a spring suspended, in-plane oscillating mass carrying an array of optical apertures. Light flux modulation is achieved with a second array of complementary apertures that is fixed to the Si frame. The investigated device comprises a sandwich structure of an SMD LED, the MEMS aperture gratings, and a phototransistor. Relative displacements of the gratings generate a modulation of the LED light flux that is detected by the phototransistor. Depending on the aperture design, the relative displacement may extend over several tens of microns maintaining a sub-nm resolution. Thus, no closed-loop position control system is required, resulting in minimum complexity and energy consumption of the MEMS component. This setup simplifies the manufacturing process as much as possible, which is one of the significant advantages of the sensor principle. Furthermore, the presented prototype exhibits a promising high sensitivity of 60 nA/nm for displacement, featuring a noise level of about 8 pm/√Hz.

Contrary to present external microphones, the proposed middle ear microphone does not measure the sound pressure but the acoustic deflection of a middle ear bone caused by an incoming pressure wave at the ear drum. By means of a seismic inertial transducer, minute vibrations in the range from 0.1 to 10 kHz should be measured. The innovation of our new capacitive sensor design is the consideration of the physiology of the ear and hearing characteristics enabling the detection of the ossicle’s vibration more than one decade below the eigenfrequency of the transducer. Additionally, the output dynamic is reduced. Hence, the demands on the signal processing unit are lowered. Finally, this approach leads to lower susceptibility to gravity and instability caused by electrostatic forces.

This work reports a novel construction of a micromachined MEMS magnetometer detecting static magnetic fields of CERN's reference dipole with a custom made capacitive read-out. The magnetic flux density is characterized via 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 thin film metal electrodes are separated by a small gap, building 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. By knowing the electrical current, 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, of course, 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.

9th Annual IEEE International Systems Conference (SysCon), 13-16 April 2015 Vancouver, BC Air conditioning systems are among the major energy consumers in buildings. Energy-efficient operation of AC systems is an important step towards better energy management in building automation, but requires efficient monitoring of the energy or enthalpy flows within the AC installation, which is currently still difficult because of the lack of appropriate equipment. This paper introduces a distributed data acquisition system for large-scale AC systems based on low-cost flow sensors implemented by means of standard printed circuit board technology and interconnected via a wireless sensor network. A critical issue for the system installation is the placement of the sensors in the air ducts to obtain representative measurements of the air flow. To this end, extensive aerodynamical simulations are carried out to analyze the flow distributions in typical building blocks for air ducts, particularly with respect to turbulences. The simulation results are compared with experimental data from the literature and are shown to be reliable. Energie-Umweltmanagement Forschung Burgenland

A completely passively operating micro-mechanical switch is presented. The switch composes of a thermal actuator and a curved bistable beam. The actuator comprises V-shaped beams and a lever transmission. It is designed to operate passive only relying on the thermal expansion of the active material (electroplated Ni) and the temperature changes of the surrounding environment, where the temperature ranges from 40°C up to +50°C. The actuator exhibits a temperature dependent deflection sensitivity of 0.9 μm/K and sufficient force to push the bistable beam into is secondary position. Both subsystems are connected via a latching mechanism. A temperature difference of at least 35 K is required for activation of the switch. A self tailored measurement setup is used to quantify the temperature dependent deflections by means of an optical principle. The measured results are in good agreement with results of numerical simulations and analytical models.

A concept of a flow sensor optimized for the use in HVAC (Heating Ventilating Air Conditioning) systems is presented. The fabrication of the transducer is based on PCB (Printed Circuit Board) technology to keep costs low and allow for easy handling and replacement. The complete sensor device consists of a quantizer, a conversion circuitry, and a network link. Through interaction with the streaming fluid, the transducer generates an electrically measurable signal which allows determination of the total flow of the fluid. The measurement principle is based on a modification of the calorimetric principle. Hence, miniaturized heat sources and nearby temperature detectors have to be implemented. The behavior and performance of the sensor concept has been studied by means of finite element simulations. The quasistatic and transient simulations reveal the temperature allocation inside the sensor and the surrounding fluid and therefore allow a further optimization of the sensor for different applications.

We present a novel design of a resonant magnetic field sensor with capacitive read-out permitting wafer level production. The device consists of a single-crystal silicon cantilever manufactured from the device layer of an SOI wafer. Cantilevers represent a very simple structure with respect to manufacturing and function. On the top of the structure, a gold lead carries AC currents that generate alternating Lorentz forces in an external magnetic field. The free end oscillation of the actuated cantilever depends on the eigenfrequencies of the structure. Particularly, the specific design of a U-shaped structure provides a larger force-to-stiffness-ratio than standard cantilevers. The electrodes for detecting cantilever deflections are separately fabricated on a Pyrex glass-wafer. They form the counterpart to the lead on the freely vibrating planar structure. Both wafers are mounted on top of each other. A custom SU-8 bonding process on wafer level creates a gap which defines the equilibrium distance between sensing electrodes and the vibrating structure. Additionally to the capacitive read-out, the cantilever oscillation was simultaneously measured with laser Doppler vibrometry through proper windows in the SOI handle wafer. Advantages and disadvantages of the asynchronous capacitive measurement configuration are discussed quantitatively and presented by a comprehensive experimental characterization of the device under test.

The motion of the seismic mass that is induced by thermal noise limits the resolution of typical micromachined vibration sensors. Its value can be adjusted by the size of the proof mass which is also a quantity for the inertial actuation input. Owing to a novel transduction concept, micro-opto-electro-mechanical vibration sensors featuring approximately twice as much mass per chip area are feasible, while decreasing the technological efforts during fabrication. The essence of the devised sensor principle is the modulation of the intensity of a light flux propagating perpendicularly through a pair of micromachined apertures. One aperture is fixed to the encapsulation and the second one is deffected by inertial forces. Earlier attempts have employed opto-electrical transmitters and receivers operating at a wavelength where silicon is intransparent. Thus, openings in the silicon mass were necessary. The presented evaluation technique utilizes the transparency of silicon in the infrared region at wavelengths well above 1.1 μm. In contrast to the previously used optoelectronic components, an InGaAs LED and an InGaAs pin-diode were integrated. This all enables of thin-film metal apertures deposited on top of the silicon seismic mass instead of etched silicon windows. Beside the increase in mass, this approach offers larger scope for design and implies a reduced damping coefficient yielding an improved quality factor. A structure for the proof of concept was fabricated and characterized together with a sensor based on the preceding principle. The results are in good agreement with the predicted behavior and the parameters tested by FEM analysis considering the fabrication related underetching as well.

A thermal actuator based on two symmetrical V-shaped beam stacks (also called chevron-type) is presented. Each beam stack consists of 6 beams in parallel. The stacks are coupled facing each other and are slightly shifted along the mirror axis. Both stacks are connected to a lever beam. Due to the thermal expansion of the material, the tip of the lever moves up and downwards perpendicular to the mirror axis. The device is built up of galvanic deposited nickel. Finite element simulations were carried out for design considerations prior to the manufacturing of the device. The simulations were used to optimize the design regarding to the sensitivity and the maximum mechanical stress to be expected. The stress level needs to be lower than the yield strength of the material, to prevent plastic deformation and, therefore, irreversible tip defections. This also limits the overall sensitivity of the design. First results of the device with 400 µm long bent beams show a linear behavior and a sensitivity of 0.5 μm/K and expectable forces of 66 μN/K in a temperature range of -30°C up to +40°C.

A miniaturised, piezoelectrically driven shaker system is presented which is suitable for MEMS characterisation in vacuum. It offers a broad frequency and amplitude range. The fully vacuum compatible shaker is constructed out of one single peace of aluminium with a piezo-stack-actuator working in-plane against four beam springs. It can easily be fabricated at low costs using a hand operated milling machine. The systems characteristics are easily tuned to different applications as the first resonance frequency is given by the stiffness of the beam springs and the mass of the moving shaker table. The utilised piezoelectric stack determines the maximum reachable amplitude for a given spring stiffness. Finite Element simulations have been carried out to design a at transfer characteristic of the shaker up to 10 kHz and amplitudes in the range from sub nanometres up to 1μm. The simulations were evaluated by laser vibrometer measurements of the shaker which also show a good linearity between electrical excitation signal and output deection amplitude. To account for other resonance frequencies introduced by a preexisting MEMS mounting device, the resulting vibration amplitude on the MEMS structure can be normalised by adjusting the electrical excitation amplitude with the help of a Polytec laser vibrometer.

Light flux modulators based on micro-opto-electro-mechanical systems (MOEMS) enable high resolution displacement based inertial sensors. The three major noise sources for such devices are the Brownian noise originating from the surrounding air, the noise emerging from the optoelectronic detector and the noise contributed by the amplifier circuit. To unveil the resolution limiting mechanisms, we investigated the performance of a transimpedance amplifier in relation to opto-electrical receivers. To verify this approach, a SPICE simulation model including all noise sources was set up and compared with measurements. The experimental data suggest that the noise of the utilized transimpedance amplifier can be optimized for a given dynamic resistance and noise current of a given photoreceiver.

Micro mechanical light flux modulators enable high resolution inertial displacement sensors that are virtually free from reaction forces. The presented MOEMS (Micro-Opto-Electro-Mechanical System) transducer modulates the light flux of an LED by the relative movement of two aperture gratings one etched into a seismic mass and the other fixed to the sensor package. The modulated flux is registered by a photo transistor and amplified using a transimpedance amplifier. Theoretical examinations suggested that apertures featuring a high aspect ratio are performing best. Applying these design rules, an increase in sensitivity by a factor 4.72 to 0.532 μA/nm at a frequency of 10 kHz and an improvement in displacement resolution from 10.7 pm/ √Hz to 2.26 pm/ √Hz was found when compared to prior prototypes featuring a comparable mechanical characteristic. The system was also found to follow a linear characteristic over the tested amplitude range.

Light flux modulators based on micro-opto-electromechanical systems (MOEMS) enable high resolution displacement based inertial sensors. To unveil the resolution limiting mechanisms, we investigated the performance of modulators with a rectangular aperture design. The two major noise sources for such devices are the Brownian noise originating from the surrounding air and the noise emerging from the opto-electronic photodetector. The experimental data suggests that the noise equivalent displacement is determined by the transmitive aspect ratio of the aperture.

Although capacitive and piezoresistive readouts are commonly used for microelectromechanical structures, they suffer from serious drawbacks like limited range of displacement, inherent nonlinearity, insucient sensitivity, and technological complexity. Our complementary readout approach relies on a novel hybrid optomechanical device, where the displacement range is not limited by typical constraints of capacitive or piezoresistive conversion principles. Furthermore, no electrical connections are required on the micromechanical part. Moreover, this principle enables custom linear or nolinear output characteristics at the same technological effort.

In this work a competitive OMEMS (optical micro electromechanical system) readout for displacement is presented. Congruent positioned gratings modulate the light flux caused by a relative in-plane displacement. As demonstrator, an inertial sensor is used. Consisting of a Si-chip bearing a perforated and spring suspended MEMS structure (seismic mass), which is bonded with SU8 to a glass chip featuring vapor deposited Cr-pattern. Both form a partially transparent sandwich structure where the transmittance depends on the position of the suspended Si mass. The modulated light flux is generated and detected by an SMD-LED and a phototransistor at the top and bottom side of the sandwich structure, respectively. First results show a high sensitivity of 21 mV/nm displacement of the seismic mass featuring a noise level of about 200 pm/√Hz.

We present a competitive OMEMS (optical micro electromechanical system) readout for displacement. Congruent positioned gratings modulate the light flux caused by a relative in-plane displacement. As demonstrator, an inertial sensor is used consisting of a Si-chip bearing a perforated spring suspended MEMS structure (seismic mass), which is bonded with SU8 to a glass chip featuring vapor deposited Cr-pattern. Both form a partially transparent sandwich structure where the transmittance depends on the position of the movable Si mass. The modulated light flux is generated and detected by an SMD-LED and a phototransistor at the top and bottom side of the sandwich structure, respectively. First results show a high sensitivity of 10 mV/nm displacement of the seismic mass featuring a noise level of about 200 pm/√Hz.