This PDF file contains the front matter associated with SPIE Proceedings Volume 7362, including the Title Page, Copyright information, Table of COntents, Introduction (if any), and the Conference Committee listing.

This paper presents, for the first time, a coupled piezoelectric-circuit finite element model (CPC-FEM) to analyze the power output of vibration-based piezoelectric energy harvesting devices (EHDs) when connected to a resistive load. Special focus is given to the effect of the resistive load value on the vibrational amplitude of the piezoelectric EHDs, and thus on the current, voltage, and power generated by the EHDs, which are normally assumed to be independent of the resistive load in order to reduce the complexity of modelling and simulation. The CPC-FEM presented uses a cantilever with the sandwich structure and a seismic mass attached to the tip to study the following load characteristics of the EHD as a result of changing the load resistor value: (1) the electric outputs of the EHD: current and voltage, (2) the power dissipated by the resistive load, (3) the vibration amplitude of tip displacement, and (4) the shift in resonant frequency of the cantilever. Significant dependences of the characteristics of the piezoelectric EHDs on the externally connected resistive load are found, rather than independency, as previously assumed in most literature. The CPC-FEM is capable of predicting the generated power output with different resistive load values while simultaneously considering the effect of the resistor value on the vibration amplitude. The CPC-FEM is invaluable for validating the performance of a device before fabrication and testing, thereby reducing the recurring costs associated with repeat fabrication and trials, and also for optimizing device design for maximal power-output generation.

This paper deals with an electromagnetic vibration energy harvester which generates electrical energy from ambient vibrations. This harvester provides an autonomous source of energy for wireless applications, with an expected power consumption of several mW, placed in an environment excited by ambient vibrations. A tuned up design of the harvester with an electromagnetic converter provides sufficient generating of electrical energy for wireless applications. The output power depends on a frequency and level of the vibration and sensitivity of the energy harvester. Our harvester includes a unique spring-less resonance mechanism where stiffness is provided by repelled magnetic forces. The sensitivity is affected only by friction forces inside the mechanism of the harvester. Ways of decreasing friction, it means an increasing sensitivity, are investigated in this paper. The increasing sensitivity of the harvester provides more generated energy or decrease of the harvester size and weight.

One of the main requirements in wireless sensor operation is the availability of autonomous power sources sufficiently compact to be embedded in the same housing and, when the application involves living people, wearable. A possible technological solution satisfying these needs is energy harvesting from the environment. Vibration energy scavenging is one of the most studied approaches in this frame. In this work the conversion of kinetic into electric energy via piezoelectric coupling in resonant beams is studied. Various design approaches are analyzed and relevant parameters are identified. Numerical methods are applied to stress and strain analyses as well as to evaluate the voltage and charge generated by electromechanical coupling. The aim of the work is increasing the specific power generated per unit of scavenger volume by optimizing its shape. Besides the conventional rectangular geometry proposed in literature, two trapezoidal shapes, namely the direct and the reversed trapezoidal configuration, are analyzed. They are modeled to predict their dynamic behavior and energy conversion performance. Analytical and FEM models are compared and resulting figures of merit are drawn. Results of a preliminary experimental validation are also given. A systematic validation of characteristic specimens via an experimental campaign is ongoing.

Micropelt develops and markets the world's smallest thermoelectric power generation devices. Due to the silicon-wafer based MEMS-like production process elements with a total thickness of 1 mm and a footprint from less than 1 mm² to 25 mm² can be realized. The fabrication process is based on standard semiconductor equipment and processes. Therefore ramp-up schemes and economies-of-scale close to those of common chip devices apply to Micropelt products. Micropelt thermogenerators produce much higher output voltages than conventional bulk devices which is due to the fact that their micro-structuring technology produces near 8000 p-n thermo-couples per square centimeter, while conventional thermogenerators typically have less than 10 such thermo-couples on the same area. Consequently Micropelt generators are well suited as the core of an integrated power supply for energy-autonomous miniaturized smart systems with average power consumptions of a few Milliwatts. Micropelt Engineering has proven readiness of their devices for use in a multitude of wireless sensor and micro systems, including smart actuators In this paper we will first introduce the Micropelt technology and further discuss energy harvesting opportunities for novel low power devices and wireless applications based on given waste heat reservoirs.

Wide bandgap materials like SiC, ZnO, AlN form a strong platform as transducers for biosensors realized as e.g. ISFET (ion selective field effect transistor) devices or resonators. We have taken two main steps towards a multifunctional biosensor transducer. First we have successfully functionalized ZnO and SiC surfaces with e.g. APTES. For example ZnO is interesting since it may be functionalized with biomolecules without any oxidation of the surface and several sensing principles are possible. Second, ISFET devises with a porous metal gate as a semi-reference electrode are being developed. Nitric oxide, NO, is a gas which participates in the metabolism. Resistivity changes in Ga doped ZnO was demonstrated as promising for NO sensing also in humid atmosphere, in order to simulate breath.

The fast and direct identification of possibly pathogenic microorganisms in air is gaining increasing interest due to their threat for public health, e.g. in clinical environments or in clean rooms of food or pharmaceutical industries. We present a new detection method allowing the direct recognition of relevant germs or bacteria via fluorescence-labeled antibodies within less than one hour. In detail, an air-sampling unit passes particles in the relevant size range to a substrate which contains antibodies with fluorescence labels for the detection of a specific microorganism. After the removal of the excess antibodies the optical detection unit comprising reflected-light and epifluorescence microscopy can identify the microorganisms by fast image processing on a single-particle level. First measurements with the system to identify various test particles as well as interfering influences have been performed, in particular with respect to autofluorescence of dust particles. Specific antibodies for the detection of Aspergillus fumigatus spores have been established. The biological test system consists of protein A-coated polymer particles which are detected by a fluorescence-labeled IgG. Furthermore the influence of interfering particles such as dust or debris is discussed.

Here we present a comparison between polycrystalline AlN and (100) silicon as a support for the development of an immunosensor. A covalent approach was followed for the modification of the initially oxidized surfaces. First a layer of epoxy-based silane organic molecules was deposited. Next, protein A was immobilized with the purpose of taking advantage of its ability to properly orient the antigen binding sites of IgG antibody molecules. Finally the antibodyantigen reaction was accomplished using rabbit IgG and a corresponding antigen, such as anti-rabbit goat IgG. The antirabbit goat IgG was labelled with HRP. This allowed us to quantify the quantity of immobilized antigen. Our results demonstrate the reliability of polycrystalline AlN as a platform for immunosensing, with results comparable to those of silicon.

The behaviour of AlN self-actuated beams for potential applications in the field of resonant sensors is analyzed focusing on the characterization of the quality factor. This study is extended to high-order modes up to 7 MHz. Laser Doppler vibrometry and impedance analysis were the measurement techniques used. For the former, the quality factor (Q factor) is deduced from both, the frequency response and the transient response. The impedance measurement is not possible for all the modes due to the symmetry in the modal shape, but when it can be measured, the Q factor may be deduced either from the characteristic frequencies of the resonance or from the equivalent resonant circuit. All the four methods yielded comparable magnitudes for the Q factor in air. In order to validate the quality of the devices, and for comparison purposes, calculations based on finite element method were utilized, and a good agreement was found with measured data, regarding modal shapes and resonance frequencies of each mode.

In this contribution, a method will be introduced to derive an envelope model for vibratory gyroscopes capturing the essential "slow" dynamics (envelope) of the system. The methodology will be exemplarily carried out for a capacitive gyroscope with electrostatic actuators and sensors. The resulting envelope model can be utilized for transient simulations with the advantage of a significantly increased simulation speed as well as for steady state simulations. Especially for the sensor design and optimization, where usually very complex mathematical models are used, efficient steady state simulations are of certain interest. Another great advantage of this approach is that the steady state solutions in terms of the envelope model are constant. Thus, for the controller design, a linearization of the nonlinear envelope model around the steady state solution yields a linear time-invariant system allowing for the application of the powerful methods known from linear control theory.

Implantable medical devices to interface with muscles, peripheral nerves, and the brain have been developed for many applications over the last decades. They have been applied in fundamental neuroscientific studies as well as in diagnosis, therapy and rehabilitation in clinical practice. Success stories of these implants have been written with help of precision mechanics manufacturing techniques. Latest cutting edge research approaches to restore vision in blind persons and to develop an interface with the human brain as motor control interface, however, need more complex systems and larger scales of integration and higher degrees of miniaturization. Microsystems engineering offers adequate tools, methods, and materials but so far, no MEMS based active medical device has been transferred into clinical practice. Silicone rubber, polyimide, parylene as flexible materials and silicon and alumina (aluminum dioxide ceramics) as substrates and insulation or packaging materials, respectively, and precious metals as electrodes have to be combined to systems that do not harm the biological target structure and have to work reliably in a wet environment with ions and proteins. Here, different design, manufacturing and packaging paradigms will be presented and strengths and drawbacks will be discussed in close relation to the envisioned biological and medical applications.

To miniaturize MEMS microphones we have developed a microphone package using flip chip technology instead of chip and wire bonding. In this new packaging technology MEMS and ASIC are flip chip bonded on a ceramic substrate. The package is sealed by a laminated polymer foil and by a metal layer. The sound port is on the bottom side in the ceramic substrate. In this paper the packaging technology is explained in detail and results of electro-acoustic characterization and reliability testing are presented. We will also explain the way which has led us from the packaging of Surface Acoustic Wave (SAW) components to the packaging of MEMS microphones.

Adhesive wafer bonding is a technique that uses an intermediate layer for bonding (typically a polymer). The main advantages of using this approach are: low temperature processing (maximum temperatures below 400°C), surface planarization and tolerance to particles (the intermediate layer can incorporate particles with the diameter in the layer thickness range). Evaporated glass, polymers, spin-on glasses, resists and polyimides are some of the materials suitable for use as intermediate layers for bonding. The main properties of the dielectric materials required for a large field of versatile applications/designs can be summarized as: isotropic dielectric constants, good thermal stability, low CTE and Young's modulus, and a good adhesion to different substrates. This paper reports on wafer-to-wafer adhesive bonding using SINR polymer materials. Substrate coating process as well as wafer bonding process parameters optimization was studied. Wafer bonds exceeding the yield strength of the SINR polymer were accomplished on 150 mm Si wafers. Features of as low as 15 μm were successfully resolved and bonded. A unique megasonic-enhanced development process of the patterned film using low cost solvent was established and proven to exceed standard development method performance. Statistical analysis methods were used to show repeatability and reliability of coating processes.

We report on a novel technique to control the resonance frequency of polymer membranes, without additional external actuators. An electrostatic force is used to apply compressive stress to a dielectric electroactive polymers membrane, consisting of a 25 micron thick, 1 to 4 mm diameter, polydimethylsiloxane (PDMS) film bonded onto patterned silicon or Pyrex wafers. Both sides of the membranes are rendered conductive by low-energy metal ion implantation. Ion implantation is chosen because it stiffens the membrane much less than sputtering a film of similar thickness [1][2]. The initial resonance frequency of the membrane is given by its geometry, the Young's modulus and stress of the composite film. The technique presented here allows tuning the resonance frequency from this initial value down to zero (at the buckling threshold) by adding compressive stress due to a voltage difference applied to the electrodes on both sides of the membrane. We have measured a reduction of the first mode resonance frequency of up to 77% (limited by dielectric breakdown) for ion-implanted membranes [3]. The tuning is repeatable and allows for continuous variation. Excellent agreement was found between our measurements and an analytical model we developed based on the Rayleigh-Ritz theory.

This paper presents results from a few tactile sensors we have designed and fabricated. These sensors are based on a common approach that consists of placing a sheet of piezoresistive material on the top of a set of electrodes. If a force is exerted against the surface of the so obtained sensor, the contact area between the electrodes and the piezoresistive material changes. Therefore, the resistance at the interface changes. This is exploited as transconduction principle to measure forces and build advanced tactile sensors. For this purpose, we use a thin film of conductive polymers as the piezoresistive material. Specifically, a conductive water-based ink of these polymers is deposited by spin coating on a flexible plastic sheet, giving as a result a smooth, homogeneous and conducting thin film on it. The main interest in this procedure is it is cheap and it allows the fabrication of flexible and low cost tactile sensors. In this work we present results from sensors made with two technologies. First, we have used a Printed Circuit Board technology to fabricate the set of electrodes and addressing tracks. Then we have placed the flexible plastic sheet with the conductive polymer film on them to obtain the sensor. The result is a simple, flexible tactile sensor. In addition to these sensors on PCB, we have proposed, designed and fabricated sensors with a screen printing technology. In this case, the set of electrodes and addressing tracks are made by printing an ink based on silver nanoparticles. There is a very interesting difference with the other sensors, that consists of the use of an elastomer as insulation material between conductive layers. Besides of its role as insulator, this elastomer allows the modification of the force versus resistance relationship. It also improves the dynamic response of the sensor because it implements a restoration force that helps the sensor to relax quicker when the force is taken off.

So-called dielectric elastomer (DE) actuators represent today one of the best performing technologies for electroactive polymer based actuation. This paper presents the concept for a new of class of DE actuators, with attractive potential capabilities for specific application needs. The proposed actuators use an incompressible fluid to mechanically couple an active elastic part with a passive elastic part. The active part works according to the DE actuation principle, while the passive part represents the end effector, in contact with the load. The fluid is used to transfer actuation hydrostatically from the active to the passive part and, then, to the load. This can provide specific advantages, including improved safety and less stringent design constraints for the architecture of the actuator, especially for its soft end effector. These might be of particular interest for many types of applications. Such a simple concept can be readily implemented according to different structures and intended functionalities of the resulting actuators. The paper describes some examples of actuators based on this concept and reports the preliminary performance of the first prototypes.

We describe the fabrication of ionic polymer-meal composites (IPMCs) containing Cu/Ni electrode as an electrode material and ionic liquid as an electrolyte. Cu/Ni is notorious for vulnerability to oxidation and acid. The authors have investigated best candidate of ionic liquids for this vulnerable electrode. This new IPMC shows increased displacement and blocking force compared to that of conventional IPMC containing Pt electrode and ionic liquid due to increased stiffness of resulting IPMC and size effect of mobile cations. In this research, the effect of ionic liquid was investigated by monitoring displacement and blocking force of IPMCs depending on the type of ionic liquids.

Aluminum nitride (AlN) is a promising piezoelectric material suitable for full CMOS compatible MEMS processes. Due to the transversal inverse piezoelectric effect the use of AlN enables quasistatic deformable mirrors by actively coupling lateral strain in micro machined membranes. In this work a fast and reliable way for reactive magnetron rf-sputtered aluminum nitride thin films with piezoelectric properties is shown. The thin AlN films were deposited on amorphous TiAl, SiO₂ and silicon substrates using an industrial PVD cluster system. The morphologies of the deposited polycrystalline AlN films are characterized by X-ray diffraction measurements and SEM images of the layer surfaces. An enhanced texture coefficient is used to demonstrate the correlation between the X-ray diffraction pattern and the surface topology. High values of this enhanced texture coefficient will guarantee piezoelectric properties. Virtual powder X-ray diffraction experiments are used to determine the relative powder intensities required for texture coefficient evaluation. The transversal inverse piezoelectric coupling coefficient d₃₁ is measured for tempered and untreated aluminum nitride thin films with high enhanced texture coefficients by quasistatic deflected wafer cantilevers.

Micro-cantilevers and micro-bridges actuated by sputter-deposited aluminium nitride (AlN) thin films were measured with a scanning laser Doppler vibrometer up to 6 MHz, covering more than 10 resonance modes of different nature. A finite element model (FEM) was used to simulate the modal response of the micromachined structures. The comparison between experiment and simulation, regarding modal shapes and frequencies, resulted in an excellent agreement, what confirmed the quality of the structures. Finally, we point out, and illustrate with the help of micro-bridges, the importance for a locally tailored distribution of electrical excitation on the top surface of the device, in order to either optimize or cancel out the displacement of a given mode.

This paper leads to a one-side-actuated piezoelectric membrane showing an upward deflection under forward bias. It is also shown that one-side-actuated piezoelectric membranes achieve comparable and higher deflections as common piezoelectric actuated membranes with similar dimensions. The piezoelectric substrate functions as complete active element, since it is both actuator and deflectable membrane, which offers an important simplification in the fabrication process.

In this work, a robust metallic amplification unit for piezoelectric microactuators is presented. The mechanism which is implemented with a sliced membrane structure made from a superelastic nickel titanium alloy is based on a mechanical lever in order to amplify the small piezoelectrically induced deformation. Therefore, increased stroke can be provided up to high frequencies. The fabrication process using laser ablation, the assembly process, the static and dynamic simulations and experimental measurements are reported. An amplification factor of 9 has been achieved for a specific load transmission point position. The dynamic response shows a quality factor of 25 at 11.97 kHz for the first mode. Compared to silicon, nickel titanium shows enhanced properties against failure and facilitates the integration process.

In this paper various non-standard methods and instruments for the functional, yield and reliability analysis of MEMS are discussed. Most of these methods are based on existing instruments, involving electrical, optical or mechanical measurements. We present either alternative applications of existing techniques, new methodology for data extraction, or adaptation/automation of the techniques for automatic chip or wafer level measurements.

In this paper, a foundry process for surface micromachined inertial sensors such as accelerometers or gyroscopes is introduced, with special attention on reliability aspects. Reliability was a major focus during the development phase, leading to the choice of the single crystalline silicon layer of an SOI device wafer as the mechanically active material. Glass frit wafer bonding is used for capping and hermetic sealing, but in addition to these fundamental reliability aspects, many influences on reliability must be considered, such as the risk of sticking, local stress concentration, electrical effects or the defined limitations of the mechanical movement in the interaction of design and technology. Reliability test results, as well as measures for improving the reliability and performance, are discussed in this paper.

Silver (Ag) is regarded as advanced material for metallization purposes in microelectronic devices because of its high conductivity and its enhanced electromigration resistance. Besides the typical use of silicon based substrate materials for device fabrication, thin film metallization on ceramic and glass-ceramic LTCC (low temperature cofired ceramics) substrates gets more and more into focus as only thin film technology can provide the required lateral resolutions of structures in the μm-range needed for high frequency application. Therefore, the reliability of Ag thin films is investigated under accelerated aging conditions, utilizing test structure which consist of 5 parallel lines stressed with a current density of 2.5.10⁶ A/cm² at temperatures ranging from room-temperature up to 300°C. To detect the degradation via the temporal characteristics of the current signal a constant voltage is applied according to the overall resistance of the test structure. Knowing the mean time to failure (MTF) and activation energy at elevated temperatures lifetime predictions can be made when extrapolating for room temperature scenarios. Applying this approach, the highest value of 6053 days is determined for Ag thin films on LTCC. When compared to Si/SiO₂ and alumina substrates the poorer performance originates from the microstructure of the films. On polycrystalline aluminum oxide Ag thin films exhibit sharp discontinuities due to a pronounced graining originating from the substrate. This effect could limit the distance of electromigration tracks.

Sb nanowires with a homogeneous distribution of diameters of about 25 nm and length up to several microns are synthesized by a FIB induced self-assembling process. In contrast to a broad class of techniques for nanowire growth, neither heating of the sample nor any additional materials source is required, thereby being compatible with on-chip microelectronics. We propose a synthesis model similar to the well known vapor-liquid-solid mechanism with Ga acting as catalyst. The vapour-liquid-solid mechanism deals with the fact that a catalytic metal particle on the sample surface forms a liquid alloy cluster if the ambient temperature is high enough and serves as the preferential site for adsorption of reactant. It is supposed that supersaturation is the driving force for nucleation of seeds at the interface between the alloy cluster and the substrate surface giving rise to a highly anisotropic growth of nanostructures. We assume that FIB processing produces mobile Ga species on the surface which rapidly agglomerate forming catalytic nanoclusters. Sputtered Sb diffuses on the surface and acts as a quasi-vapor phase source. When the solved Sb concentration exceeds saturation, nucleation sites will be formed which initiate the precipitation of the Sb. We integrated such synthesized NWs in CMOS compatible resitivity type gas sensors.

A novel micromachined thermal emitter for fast transient temperature operation is presented. Compared to most commercial available thermal emitters, the one here presented, is able to operate in a pulsed mode. This allows the use of lock-in techniques or pyrodetectors in the data acquisition without the use of an optical chopper for light modulation. Therefore, these types of thermal emitters are very important for small filter photometers. Several spider type hotplate concepts were studied in order to find a design with excellent mechanical stability and high thermal decoupling. The thermal emitters are fabricated using silicon on insulator (SOI) technology and KOH-etching. The emitters are heated with Pt-meanders. For temperature determination an additional Pt-structure is deposited onto the hotplates. The emitters are mounted in TO-5 housings using a ceramic adhesive and gold wire bonding. The used operation temperature is 750°C. In pulsed operation it's important to have a large modulation depth in terms of thermal radiation intensity in the needed spectral range. The maximal reachable modulation depth ranges from ambient temperature to steady state temperature. A modulation frequency of 5 Hz still allows using nearly the maximum modulation depth.

Innovative surfaces are successful, if we succeed to put in the correct place the correct property with technological efficiency. Until now, material surfaces can be systematically structured in different ways in order to fulfil chemical or mechanical requirements such as corrosion protection or wear resistance for example. Moreover, the properties of materials are strongly related to their microstructure as well as to their spatial distribution. For that reason, the design of materials with tailored microstructures is a key for the functionalization of surfaces. This is possible by an artificial fabrication technique called Laser Interference Metallurgy. In this context, textured or functionalized surfaces are beneficial in overcoming stiction and adhesion in MEMS devices. With regard to tribological applications, a systematic study of the effect of geometrically differing laser interference patterns on the wetting behaviour of metallic gold thin films with a thickness of about 300 nm and 125 μm thick polyimide foils should be presented. It could be shown that in case of gold films, a laser interference patterning reinforces the hydrophilic sample behavior whereas the polyimide foils reveal a significant increase in hydrophobicity after the laser patterning process. Both wetting regimes are advantageous under dry or lubricated friction conditions. The corresponding geometrical limits of the abovementioned method concerning the structure depth, periodicity and pattern form has been determined. All the samples have been characterized by scanning electron and focused ion beam microscopy and white light interferometry. Additionally, IR spectroscopy has been applied to the polyimide samples in order to separate topographic and chemical influences.

To make use of metals with improved conductivity like Ag, AgPd, Au or Cu for metallization pastes in ceramic multilayer technology, Low-Temperature Co-fired Ceramics (LTCC) are densified at temperatures below 900°C. The densification mechanism can be attributed to viscous sintering in combination with the crystallization of the glass matrix. Lifetime prediction and extension of the application range to elevated temperatures strongly depend on the transition range of the remaining amorphous phase as well as on the final crystallization products. Due to the fact that multilayer ceramics based on LTCCs are gaining increasing interest in the manufacturing of highly integrated devices for microelectronic and sensor applications, there is the need to establish a better understanding of their mechanical and electrical behaviour in the elevated temperature regime. In this study, four commercial LTCC substrate materials in addition to a test product in the sintered state, namely DP 951, DP 943, both from DuPont, CT 800 and AHT-01, both from Heraeus, and GC from CeramTec were investigated in respect to the temperature dependence of their mechanical and electrical properties up to temperatures of 950 °C. Mechanical characterization included three-point bending tests on single layer substrates. Furthermore, the surface resistivity as a function of temperature up to 500°C was determined under vacuum for DP 951. Next, these results were correlated to the composition of the glasses, determined by inductively coupled plasma (ICP) analysis, as well as the crystallization products apparent in the composites, which were determined by XRD of the sintered substrates and in-situ HT-XRD for DP 951. Results gained from these investigations of the commercial LTCC products were compared to measurements carried out on glass-ceramic composites developed in-house exhibiting improved electrical behaviour and good temperature stability.

Metal containing carbon thin films can be prepared to exhibit piezoresistive properties with a high sensitivity to mechanical strain and with a temperature independent resistance. This unique combination of properties predisposes these films to be used in sensors for pressure, force, weight and torque. For the case of nickel containing carbon films (often termed as Ni containing hydrogenated amorphous carbon, shortly Ni:a-C:H) we are able to demonstrate a strain sensitivity (gauge factor) of approx. 20 together with a temperature coefficient of resistivity (TCR) below ±50 ppm/K in the wide temperature range of 100 K to 400 K. The sensitivity of our films is thus enhanced by a factor of 10 compared with standard metallic thin films in today's sensors. The films consist of crystalline nanoclusters of nickel with a diameter of 10 - 20 nm which are encapsulated by only few atomic layers of graphene (or turbostratic graphite) as revealed by transmission electron microscopy (TEM). These carbon encapsulated clusters are embedded in a matrix of carbon. The new type of films are named nanoNi@C i.e. nano-Nickel clusters encapsulated by carbon.

Surface micromachining requires the use of easily-removable sacrificial layers fully compatible with all the materials and technological processes involved. Silicon dioxide films, thermally grown on silicon substrates or deposited by CVD, are commonly used as sacrificial layers in surface micromachining technologies, despite their low lateral etch rate in conventional fluorinate solutions. The development of silicon oxide layers with high etch rates poses a great technological challenge. In this work we have investigated the possibility of obtaining easily removable silicon oxide layers by pulsed-DC magnetron reactive sputtering. We have carried out a comprehensive study of the influence of the deposition parameters (total pressure and gas composition) on the composition, residual stress and lateral etch rate in fluorine wet solutions of the films. This study has allowed to determine the sputtering conditions to deposit, at very high rates (up to 0.1 μm/min), silicon oxide films with excellent characteristics for their use as sacrificial layers. Films with roughness around 5 nm rms, residual stress below 100 MPa and very high etch rate (up to 5 μm/min in the lateral directions), around 70 times greater than for thermal silicon oxide, have been achieved. The structural characteristics of these easily removable silicon oxide layers have been assessed by infrared spectroscopy and atomic force microscopy, which have revealed that the films exhibit some kind of porous structure, related to very specific sputter conditions. Finally, the viability of these films has been demonstrated by using them as sacrificial layer in the fabrication process of AlN-based microresonators.

In this contribution we present a novel LED-photodiode based infrared absorbance sensor in the wavelength range of 3.0 - 3.7 μm for cell analysis. Instead of using time consuming and expensive labelling and staining techniques to distinguish healthy from malignant cell types, this IR sensor system can perform faster, cheaper and without the need of additional chemicals. Depending on the used narrow bandpass filters, absorbance due to specific molecular vibration can be measured, such as the functional absorbance peaks at 3.38 μm (CH₃-antisymmetric stretch), 3.42 μm (CH₂- antisymmetric stretch), 3.48 μm (CH₃-symmetric stretch) and 3.51 μm (CH₂-symmetric stretch). For normalization and baseline correction the absorbance at wavelengths 3.33 and 3.57 μm are used. By recording the IR absorbance spectra of healthy and malignant epithelial kidney cell lines with an IR spectroscope, we found significant differences in the absorbance ratio 3.51 μm / 3.42 μm (CH₂-symmetric/antisymmetric stretch). This result has led us to a sensor concept where only four wavelengths are being measured. In the 3.0 - 3.7 μm wavelength region a low cost LED-photodiode system can be used instead of a spectroscope. Yeast cells, which also contain the CH₂ symmetric and antisymmetric stretch bands, are used to validate this sensor system and to make a first comparison of the system to spectroscopic recordings. Sensor experiments on dried spots of baker's yeast on calcium-fluoride slides yielded a comparable CH₂ stretch ratio with the IR spectroscope measurement. This confirms the usability of the sensor to measure the CH₂ stretch ratio and its potential for fast, label-free and low cost screening of cell samples.

In this paper we present the silicon comb-drive X-Y microstage with the frame-in-the-frame architecture intended to be monolithically integrated with a glass microlens as a MOEMS 2D scanner for the Miniaturized Confocal Microscope On- Chip. The microstage is characterized by relatively large travel range (± 35 μm in X-direction and ± 28 μm in Y-direction at 100 V) for a small number of driving electrodes, without noticeable mechanical X-Y crosstalk. We describe the design, ANSYS modeling, fabrication process and static characterization of the device.

We present the potential and the benefits of actuable micromirror arrays for large area applications for daylight deflection. The described micromirror arrays are intended to be implemented into windows of buildings and to provide functionalities like daylight guiding into rooms, heat regulation and glare protection. Placed between two panes of a window, these mirrors are maintenance-free and not subject to defilement. The use of micro system technology on large areas requires very low cost processes and materials, as well as a concept with a minimum of process steps and a very easy and reliable process control. We present theoretical and technological approaches and first technological results.

We present a new method for detecting the accurate position of micro-electro-opto-mechanical system (MOEMS) devices, thus enabling the implementation of closed-loop controls. The ensuing control mechanism allows building robust MOEMS-based Fourier-transform infrared (FTIR) spectrometers with large mechanical amplitudes and thus good spectral resolutions. The MOEMS mirror device, a rectangular 1.65 mm² metalized plate mirror suspended on bearing springs and driven by comb-structured electrodes, is driven by a rectangular signal with a duty cycle of 50% and high voltage levels up to 140 V at a frequency near twice its mechanical resonance frequency. Out-of-plane mirror displacements of up to ±100 μm have thus been achieved. To handle the high bandwidth of the sinusoidal mirror position reference signal, which is generated by a laser reference interferometer, an analog position detection circuit is necessary. This dedicated circuit demodulates the reference signal and generates a highly accurate control signal returning the zerocrossing position of the mirror. This permits the implementation of a closed-loop control, which ensures optimally stable MOEMS mirror movement and maximal mechanical amplitude, even under varying environmental conditions. While this solution has been developed for a specific MOEMS device, the principle is widely applicable to related components.

We achieved to etch nano- and deep structures in silicon using ICP-cryogenic dry etching process. We etched nanopores and nanocantilevers with an etch rate of 13 nm/min, nanopillars with an etch rate of 2.8 μm/min - 4.0 μm/min, membrane and cantilever structures with an etch rate of 4 μm/min and 3 μm/min, respectively. Nanopores and nanocantilevers are interesting structures for Bionanoelectronics. Nanopillars can be used as substrates/templates for the MOCVD growth of GaN nanoLEDs. They are the basic constituents of a nanoparticle balance and also of a thermoelectric generator. For the joining of the silicon wafers of the thermoelectric generator the low temperature joining technique can be used. Cantilevers can be used for sensing, e.g. as tactile cantilevers. They can be used also as resonator for mass sensing even in the subnanogram region. The actuation of the resonator can be done by using piezoelectric thin films on the cantilevers. The mass detection depends on the resonance frequency shift caused by loaded mass on the cantilevers. Such cantilevers are robust and easy to produce. The deep etching in silicon was done by using a photoresist mask and creating perpendicular and smooth sidewalls.

Most micro electro mechanical system (MEMS) microphones are designed as capacitive microphones where a thin conductive membrane is located in front of a rigid counter electrode. The membrane is exposed to the environment to convert sound into vibrations of the membrane. The movement of the membrane causes a change in the capacitance between the membrane and the counter electrode. The resonance frequency of the membrane is designed to occur above the acoustic spectrum to achieve a linear frequency response. To obtain a good sensitivity the thickness of the membrane must be as small as possible, typically below 0.5 μm. These fragile membranes may be damaged by rapid pressure changes. For cell phones, drop tests are among the most relevant reliability tests. The extremely high acceleration during the drop impact leads to fast pressure changes in the microphone which could result in a rupture of the membrane. To overcome this problem a stable protection layer can be placed at a small distance to the membrane. The protective layer has small holes to form a low pass filter for air pressure. The low pass filter reduces pressure changes at high frequencies so that damage to the membrane by excitation in resonance will be prevented.

This paper reports on test-bed for the long-term health monitoring system for bridge structures employing fiber Bragg grating (FBG) sensors, which is remotely accessible via the web, to provide real-time quantitative information on a bridge's response to live loading and environmental changes, and fast prediction of the structure's integrity. The sensors are attached on several locations of the structure and connected to a data acquisition system permanently installed onsite. The system can be accessed through remote communication using an optical cable network, through which the evaluation of the bridge behavior under live loading can be allowed at place far away from the field. Live structural data are transmitted continuously to the server computer at the central office. The server computer is connected securely to the internet, where data can be retrieved, processed and stored for the remote web-based health monitoring. Test-bed revealed that the remote health monitoring technology will enable practical, cost-effective, and reliable condition assessment and maintenance of bridge structures.

We determined the growth rate, electrical performance and morphology of tantalum (Ta) thin films in a wide range of back pressure (i.e. 0,003-0,06 mbar) and plasma power P_p (i.e. 100-900 W) levels at nominally unheated substrate conditions during deposition. First, Ta thin films with nearly constant thickness (mean value: 230 (±50) nm) were deposited by varying the sputter time in dependence of the plasma power. Next, we increased the sputter time at constant plasma power to demonstrate that we get a higher resistivity with increasing film thickness as well as at high back pressures when depositing Tantalum predominantly in the beta phase. Doing so, the resistivity of the tantalum thin films can be tailored over two decades at constant film thickness only by tuning these important deposition parameters. Furthermore, X-ray diffraction (XRD) measurements showed a decreasing grain size at samples with a higher resistivity proving the physical basis of this finding. All results can be explained based on the variation in microstructure of the thin films at different deposition parameters such as the grain size. Furthermore, when knowing the growth rate (i.e. film thickness and sputter time) the corresponding microstructure present in the Ta thin films can be estimated.

The physical and chemical behaviour of materials is strongly correlated with their microstructure. Therefore, much effort is invested in the advanced microstructural design of metallic thin films. Laser Interference Metallurgy (LIMET) is used to locally tune the grain architecture of metallic thin films from the nanoto the microscale. This means a defined size and orientation of the grains with lateral periodicity, by interfering on the sample surface two or more laser beams of a high power nanosecond pulsed Nd:YAG laser. This technique enables the local nucleation and crystallization of amorphous or nanocrystalline metallic thin films, thus combining nano- and microcrystalline regions ordered in periodic line- or lattice-like arrangements in a composite architecture. After having locally modified the microstructure of e-beam evaporated Pt and Au thin films by laser irradiation a wet chemical etching procedure was induced in hot aqua regia. Doing so, a selective etching is achieved without using conventional lithography. Due to the laser-induced recrystallization in periodic structures, these microcrystalline zones of specific oriented grains show a higher resistance against the wet chemical etchant than the as-deposited, nanocrystalline areas, which are completely removed down to the substrate. Therefore, this procedure may have the potential to be an alternative, low cost approach to conventional lithographic techniques and provides a novel method for a straight-forward patterning of metallic thin films.

Already eight years ago, the usage of piezoresistive sensors for chemical measurands was proposed at the Solid State Electronics Laboratory of the Dresden University of Technology ^[1]. Adding functionalised polymer coating which shows swelling due to chemical or biological values leads to a similar deflection of the thin silicon bending plate like for pressure sensors. The application of "stimuli-responsive" or "smart" cross-linked gels in chemical sensors is based on their ability to a phase transition under the influence of external excitations (pH, concentration of additives in water, temperature). Combining a "smart" hydrogel and a micro fabricated pressure sensor chip allows to continuously monitor the analytedependent swelling of a hydrogel and hence the analyte concentration in ambient aqueous solutions. The sensitivity of hydrogels with regard to the concentration of such additives as H⁺-ions (pH sensor), transition-metal ions, salts, organic solvents and proteins in water was investigated. It has been demonstrated that the sensor's sensitivity depends on the polymer composition as well as on the polymer cross-linking degree. Time constants down to a few ten seconds have been found for thin hydrogel films deposited directly on the backside of the silicon bending plate. In order to achieve an optimum between sensor signal amplitude and sensor response time, the gel swelling/deswelling kinetics was investigated. Some methods improving the properties of the chemical sensors have been proposed. The long-term measurements have shown that the lifetime of piezoresistive chemical sensors can be prolonged up to several years provided that specific operation and storage conditions are fulfilled.

Circular and rectangular MEMS optical scanners operating at a resonance frequencies close to 1 kHz are investigated by single-pulse digital holographic two-wavelength contouring. Coverage of the range interesting for shape measurements of micro mechanical applications like optical scanning mirrors between 10 - 100 μm using only one laser source is a challenging task. For this purpose, a dual-wavelength laser source was developed that generates two 12 nm and 34 nm separated sub-picosecond pulses around 790 nm. A Twyman-Green interferometer was extended by a polarization encoding sequence to separate the interferograms for the recording process. The two holograms were captured simultaneously introducing two CMOS-cameras in the interferometer setup. The phase difference information of the object within the synthetic wavelength of 40 μm was unambiguously generated and the 3D-shape calculated. To reliably measure the surface deformation of the oscillating mirrors the evaluation of the single phase images is sufficient. The resulting deformation of the mirrors based on the reconstructed single phase from the holograms was captured at a wavelength of λ = 783 nm. The deduced rms-values of the surface shape of the oscillating mirrors at maximum load are only ~50 nm, corresponding to a surface flatness of better than λ/10. This is an excellent result, keeping in mind that the mirror plates of the optical scanners are only ~50 μm thick. These detail information from one interferogram are combined with the coarse shape information deduced from the phase difference map of the two interferograms captured at different wavelengths. Using two-wavelength contouring only for extracting the linear slope of the mirror and combining this with the detail information of the single phase images yields a combined reconstruction. This provides a much more realistic picture of the virtually vanishing deformations of the MEMS optical scanners operated at its resonance. We are not aware of any other method that could provide equally detailed information on such a MEMS structure while simultaneously capturing such a large amplitude of the dynamics.

Carbon fiber materials become more and more important for many applications. Unlike to metal, the technological parameters and certificated quality control mechanisms have not been developed yet. There is no efficient and reliable testing system for an inline inspection and a consecutively manual inspection of the Raw Carbon Fiber materials (RCF) and the post laminated Carbon Fiber Reinforced Plastics (CFRP). Based upon the multi-frequency Eddy Current device developed at Fraunhofer IZFP structural and hidden defects such as missing carbon fiber bundles, lanes, suspensions, fringes, missing sewing threads and angle errors can be detected. Due to the help of an optimized sensor array and an intelligent image pre-processing algorithm the complex impedance signal can be allocated to different carbon fiber layers. This technique enables the possibility to detect defects in the depth up to 5 layers including the option of free scale resolution and testing frequency. Appropriate parameter lists for an optimal error classification are available. The dimensions of the smallest detectable defects are in the range of a few millimeters. A prototype of a special single sensor and an eddy-current sensor array are developed and establish the way to transfer the prototype into an industrial application.

The present study is devoted to analyze the compatibility of yttria-stabilized zirconia thin films prepared by pulsed laser deposition technique for developing new silicon-based micro devices for micro solid oxide fuel cells applications. Yttriastabilized zirconia free-standing membranes with thicknesses from 60 to 240 nm and surface areas between 50x50 μm² and 820x820 μm² were fabricated on micromachined Si/SiO2/Si3N4 substrates. Deposition process was optimized for deposition temperatures from 200ºC to 800ºC. A complete mechanical study comprising thermomechanical stability, residual stress of the membranes and annealing treatment as well as a preliminary electrical characterization of ionic conductivity was performed in order to evaluate the best processing parameters for the yttria-stabilized zirconia membranes.

In this work we report on the development of electrostatically actuated RF MEMS switches which are based on a one sided clamped cantilever made of two layers of the same alloy of aluminum-silicon-copper. The switches are based on a low-complexity design and are fabricated by conventional sputter deposition and wet etching techniques on oxidized silicon substrates. Due to a well defined intrinsic stress gradient the cantilevers bend away from the substrate surface after release. This deflection allows the combination of high open-state isolation with a moderate pull-in voltage and with high restoring forces, which help to reduce sticking effects. The temperature behavior of the residual stress of each single layer that are the basis for the switch is investigated up to 400°C. Thereby, the change in stress over temperature as well as stress level in the as-deposited state is strongly dependent on deposition parameters. Furthermore, the change of deflection is evaluated up to 400°C at cantilever-type test structures. Finally, the high frequency performance of the switches was measured in the 23 to 36 GHz range showing good results for isolation and insertion loss.

The ultimate performance of modern mechanical sensors based on bimaterial cantilevers significantly lags behind the maximum values as limited by thermal fluctuations. Even more, the signal-to-noise ratios of novel MEMS sensors fall behind the characteristics of the previous generations of mechanical sensors fabricated by macroscopic production technologies. In this paper we present for the first time a comparative analysis of the ultimate detection limits of MEMS sensors based on bimaterial cantilever displacement and detectors based of longitudinal elongation of an equivalent cantilever. The starting point of our analysis was a definition of the correspondence between the transversal displacement of a bimaterial cantilever and the longitudinal elongation of the equivalent simple cantilever. These two structures generally cannot be directly compared, since the bimaterial cantilever displacement depends on 14 variables, while the longitudinal elongation of the simple cantilever depends on 7 parameters only. However, we show that under certain conditions a full correspondence can be established between the parameters of these two structures. The expansion coefficient is used here in its general sense to describe the linear length change as a function of a given external variable, for instance temperature, analyte concentration, photonic flux, etc.

We analyzed the intrinsic noise of plasmonic sensors caused by the adsorption-desorption of gaseous analytes on the sensor surface. We analyzed a general situation when there is a larger number of different species in the environment. We developed our model and applied it to calculate various analyte mixtures, including some environmental pollutants, toxic and dangerous substances. The spectral density of mean square refractive index fluctuations follows a dependence similar to that of generation-recombination noise in photodetectors, flat at lower frequencies and sharply decreasing at higher. Some of the calculated noise levels are well within the detection range of conventional surface plasmon resonance sensors. One of the obvious conclusions is that AD noise may be an important limiting factor in monitoring process kinetics by nanoplasmonic sensors. An AD noise peak is observed in temperature dependence of mean square refractive index fluctuations, thus sensor operating temperature may be optimized to obtain larger signal to noise ratio. A significant property of AD noise is its increase with the plasmon sensor area decrease, which means that it will be even more pronounced in modern nanoplasmonic devices. Our consideration is valid both for conventional surface plasmon resonance devices and for general nanoplasmonic devices. This research could be of importance in diverse areas such as environmental sensing, homeland security, forensic applications, life sciences, etc.

This article focuses on the power consumption characteristics of a linear piezoelectric ultrasonic motor in the context of industrial mobile applications. Specifically, we analyze the power consumption of a commercially available ultrasonic motor through the analysis of a phenomenological model that has been derived using only the motor geometry and material data. The model is shown to provide rapid assessment of ultrasonic motors in a variety of disparate industrial applications while exhibiting good fidelity when compared with measured transient performance. Additionally, the model could be easily extended to other ultrasonic motor designs due to the generic nature of the model structure.

A systematic approach for flatness-based motion planning and feedforward control is presented for the transient shaping of a piezo-actuated rectangular cantilevered plate modeling an adaptive wing. In the first step the consideration of an idealized infinite-dimensional input allows to determine the state and input parametrization in terms of a flat or basic output, which is used for a systematic motion planning approach. Subsequently, the obtained idealized input function is projected onto a finite number of suitably placed Macro-fiber Composite (MFC) patch actuators. The tracking performance of the proposed approach is evaluated in a simulation scenario.

The investigation of a novel sensor system, integrated in the main load region of forming machines, is the challenge. Therefore it is important that the thin film system is multifunctional. It has an excellent tribological quality in combination with a piezoresistive behaviour. The layer system is deposited on the polished surface of a steel substrate. It has such geometries that it can be easily integrated in the drawing cushion of a deep drawing machine. The thin film sensor system exists out of a piezoresistive hydrogenated carbon layer, deposited in a PACVD process. Onto this layer arrays of chromium structures are deposited in a PVD process. The structures are protected against wear by an insulating silicon doped hydrogenated carbon layer. The whole thin film system has a thickness of about 9 μm. During the forming process the steel plate is in direct touch with the sensor system and moves over it. The position of the steel and the load distribution is measured in dependence on the forming stadium. The sensor system works as a control system to ensure that the shape of the product is perfect and without any cracks or creases.

A low-temperature hydrothermal process for the growth of ZnO nanostructures on patterned Si substrates was investigated with the aim of their future exploitation as functional cores of nanopiezotronic applications. The study focused on understanding the role of the growth factors in order to better control the suggested process and to introduce it as a low-cost, repeatable and reliable method for large-scale ZnO nanorod production. The parameters that were examined were: (a) the role of the substrate, and (b) the concentration of the metal precursor in conjunction with the growth temperature and time.

The polymer Parylene has proved to be very suitable as membrane material in many applications, because it exhibits a low Young's modulus, is biocompatible and non-conducting. A drawback, however, is that intrinsic stress reduces the flexibility of the membrane. In order to minimize the intrinsic stress and to extract the proper material parameters as inevitable input for reliable FE simulations, we investigated two Parylene derivatives (Parylene C and Parylen HT) fabricated by two different releasing procedures (plasma etching and KOH etching). To this end, we produced teststructures, measured the deflection under various pressure loads applying white light interferometry (load-deflection measurement) and extracted the Young's modulus and the intrinsic stress of the Parylene layers by fitting the measurement results to both an analytical model and FE (finite element) simulations. The results were then verified by detailed measurements of the bending lines. Our investigations revealed that Parylen C membranes released via KOH etching show a nearly unchanged Young's modulus and nearly no intrinsic stress. Plasma etched Parylene C and Parylene HT, however, exhibit a not negligible modification of the Young's modulus of 30% and 20%, respectively, and a noticeable amount of tensile intrinsic stress of 14.4 MPa and 1 MPa, respectively. By thoroughly comparing the results obtained for the different Parylene variants, we were able to identify the change in crystallinity induced by the temperature load during plasma etching as the primary cause for intrinsic stress formation in Parylene membranes.

Aluminium nitride (AlN) reactively sputter deposited from an aluminium target is an interesting compound material due to its CMOS compatible fabrication process and its piezoelectric properties. The crystal structure obtained during sputtering is a very importance criterion to obtain a good piezoelectric performance. To demonstrate this, we focused our investigations on two types of films. The first type shows a good c- axis orientation with round grain geometry. The second type is (101) oriented having a triangular grain shape. For measuring the out-of-plane displacements for dij determination, a MSV 400 Polytec scanning laser Doppler vibrometer was used. To obtain the piezoelectric constants d33 and d31 a fitting procedure between experimental and theoretical predicted results is used. Effective values for d33 and d31 in c-axis oriented films are about 3.0 pm/V and -1.0 pm/V, respectively. By contrast, films with (101) orientation show a lower effective longitudinal piezoelectric coefficients, consistent with this different orientation. Finally, both types of AlN layers were deposited on 640 μm long micro-cantilevers. The average displacement of the first mode on the vertical axis was about 12 nm for the film with good c -axis orientation and 0.3 nm for that with (101)- orientation when applying the same excitation.

This paper presents a micro-magnetometer based on the fluxgate principle. Fluxgates detect the magnitude and direction of DC and low-frequency AC magnetic fields. The detectable flux density typically ranges from several 10 nT to about 1 mT. The introduced fluxgate sensor is fabricated using MEMS-technologies, basically UV depth lithography and electroplating for manufacturing high aspect ratio structures. It consists of helical copper coils around a soft magnetic nickel-iron (NiFe) core. The core is designed in so-called racetrack geometry, whereby the directional sensitivity of the sensor is considerably higher compared to common ring-core fluxgates. The electrical operation is based on analyzing the 2nd harmonic of the AC output signal. Configuration, manufacturing and selected characteristics of the fluxgate magnetometer are discussed in this work. The fluxgate builds the basis of an innovative angular sensor system for a parallel robot with HEXA-structure. Integrated into the passive joints of the parallel robot, the fluxgates are combined with permanent magnets rotating on the joint shafts. The magnet transmits the angular information via its magnetic orientation. In this way, the angles between the kinematic elements are measured, which allows self-calibration of the robot and the fast analytical solution of direct kinematics for an advanced workspace monitoring.

Acoustoelectronic devices based on surface acoustic wave (SAW) technology are primarily used in radio frequency filters, delay lines, duplexers, amplifiers and RFID tags. Thereby, SAW's are excited at the surface of piezoelectric materials (e.g. Quartz, LiTaO₃, LiNbO₃) by an RF signal applied via interdigital transducers (IDTs)¹. Novel SAW applications that emerged recently in the field of microfluidics such as the handling of minimum quantities of fluids or gases^2,3 require a fluid compatible design approach, high power durability and long lifetime of the devices. However, conventional SAW devices with finger electrodes arranged on top of the chip surface experience acoustomigration damage^4,5 at high power input and/or higher operating temperature leading to failure of the device. Additionally, inappropriate material systems or chip surface topography can limit their performance in microfluidic application. To overcome these limitations the electrodes can be buried in an acoustically suited ("SAW-grade") functional layer which moreover should be adjustable to the specific biotechnological task. Depending on the properties of this layer, it can suppress the acoustomigration impact⁶ and improve the power durability of the device. Also, a reduction of the thermally-induced frequency shift is possible⁷. The present paper describes a novel SAW based chip technology approach using a modular concept. Here, the electrodes are buried in surface polished SAW-grade SiO₂ fabricated by means of reactive RF magnetron sputtering from a SiO₂- target. This approach will be demonstrated for two different metallization systems based on Al or Cu thin films on 128° YX-LiNbO₃ substrates. We also show the application of the SiO₂-layer with respect to compensation of thermallyinduced frequency shift and bio /chemical surface modification. Investigations were carried out using atomic force microscopy, laser-pulse acoustic measurement, glow-discharge optical emission spectroscopy, spectral reflectometry, variable angle ellipsometry and x-ray photoelectron spectroscopy. The electrode edge covering of sputter deposited SiO² layers and the reactive ion etching of the SiO₂ layers are also discussed. This modular technology gives the possibility to improve the compatibility of surface acoustic wave devices to microfluidics and generally allows the integration of SAW driven actuators (pumps and mixing devices) and sensors (sensitive to surface mass change or complex viscosity change) together with other microfluidic elements (e.g. electrophoresis, heating elements) on one chip.

This paper deals with the design of the power management circuit for the vibration generator developed in the frame of the European WISE project and its testing in the connection with the generator and the dynamic load simulating the real load. This generator is used as an autonomous energy source for wireless sensor applications. It can be used for example in the aeronautic, automotive and many other applications. The generator output power analysis was based on the vibration spectrum measured on the helicopter engine, provided by the consortium EADS, EUROCOPTER, DASSAULT AVIATION - 6.RP -WIreless SEnsing (WISE) project. This spectrum shows very unstable vibration levels. It was done the statistical analysis of these vibration levels and it was shown that there is a need of the power management circuit, which can provide a stable output voltage for the supplied circuit and if there is a need it can store an immediately unusable generated energy. The generator can't be used as the only energy source for the sensor circuit, because there are not any vibrations when for example a motor is stopped. In these periods and in the time of low vibration levels the circuit must be supplied from battery. The power management circuit described in this paper fulfills these requirements. It has two power inputs - the battery and the generator. It can switch between them at certain defined generator output levels by the threshold detector. Also when there is too much of the generated power, it can store the extra energy in the storage for the later usage. The storage device is the advanced capacitor. The advanced capacitor is a device containing three capacitors. These capacitors are connected (and charged) sequentially so the increasing capacity is provided. The developed power management was tested in the connection with the real vibration generator raised by stable vibration levels and the dynamic load simulating the real sensor in the main operation stages - sampling and data transmitting. It was shown that the generator with output power of 8mW@0,3GRMS with generator weight of 140g together with the described power management circuit can save about 50% of battery energy with the mentioned vibration spectrum. The generator used for the testing was improved, so it is more sensitive and also the sensor power requirements were decreased, so now it can be saved up to 100% battery energy during the generator operation. Also the power management circuit is still refined.