In this article we present a study of deposition and etching techniques of germanium (Ge) and amorphous oxygen germanium (GeO_x) films, with the aim of using them as sacrificial layer in the fabrication of AlN-based MEMS by surface micromachining processes. The Ge and GeO_x layers were deposited by RF magnetron sputtering in Ar and Ar/O₂ atmospheres. By controlling the process parameters we were able to set the final composition of the GeO_x films, which was assessed by FTIR measurements. We have studied the etch rates of GeO_x films with x ranging from 0 to 1 in H₂O₂ and H₂O₂/acid solutions. Depending on the etching temperature and the oxygen content in the layers, etch rates ranging from 0.2 to 2 μm/min were obtained. Nearly stoichiometric germanium oxide (GeO2) was etched in pure H₂O at very high rate (>1 μm/min at room temperature). We have also developed a chemomechanical polishing (CMP) process for the planarization of Ge and GeO_x. The influence of the slurries containing diverse powders (CeO₂, Al₂O₃) and chemical agents (NH₄OH, HCl), the different pads, and the various process parameters on the removal rate and the final sample topography has been studied. Finally, we have analysed the compatibility of the materials involved in the process flow with the processes of planarization and removal of the sacrificial layers.

Aluminum nitride is lately being considered as a promising candidate for its use as the actuator in piezoelectrically-actuated MEMS due to its good piezoelectric and mechanical properties, high chemical stability and full compatibility with conventional silicon technologies. In this work we present the mechanical response of doubly-clamped microbridges with piezoelectric actuation by a sputtered AlN film. A complete technology for the fabrication of the microbridges on silicon substrates using surface micromachining has been developed. The mechanical response of the microbridges under electrical excitation has been measured. Finite element method (FEM) computations have been carried out in order to analyze the static and dynamic response of devices with several configurations and to determine their optimum design. These simulations include the influence of the properties of the materials, the initial residual stress and the different geometries on the device operation. Although the qualitative behavior of the microbridges is well predicted, a significant discrepancy is observed between the measured displacement of the beam and the simulated response. The measured values of the out-of-plane displacement of the bridge are near ten times greater than those obtained in the simulations. Some of the possible causes of these discrepancies are widely discussed.

TiO₂ dot and rod shaped colloidal nanocrystals (NCs) prepared by an hydrolytic colloidal route and capped with different surfactants have been spin coated onto gold substrates and onto quartz slides. Morphological, structural and optical characterization of the colloidal NCs and the thin films has been performed by means of Atomic Force Microscopy (AFM), X-ray Diffraction (XRD) and UV-VIS spectroscopy. Surface Plasmon Resonance (SPR) has been used as optical transduction method to test the sensing ability of the prepared films for alcohols vapours detection as a function of NC shape, capping molecule and thermal treatment.

BaTiO₃ thin films are commonly used as a pyroelecrtic sensor because this material has a good dielectric, ferroelectric and piezoelectric properties. This paper reports the pyroelectric sensor performance of BaTiO₃/SiO₂ nanocomposite thin films. The BaTiO₃ nanoparticles were synthesized and deposited as nanocomposite thin films on Si/SiO₂ substrates using spin coating technique. The deposited films were dried at 200 °C for 2 hours and annealed at 700 °C for 1 hour in air. Pyroelectric performance of the fabricated sensors was carried out at temperature in the range of 30 to 58 °C using short-circuit current method. The heating rate was set up to 0.4 °C/s. It was found the devices showed the pyroelectric response when heated and the pyroelectric coefficients of the devices are in the range of 43-1300 μC cm^-2 K^-1.

Polymer helices with submicron dimensions have been fabricated from a variety of isotropic and liquid crystalline polymers with storage moduli ranging from 38MPa to 1.9GPa (measured at 1Hz, room temperature). These helices are made using a double templating process, in which a thin film comprised of independent helical structures deposited using glancing angle deposition (GLAD) acts as the master. In our process the 'positive' structure of the master is copied into a polymer 'negative', which then itself acts as a template for the final film of polymer helices. Liquid crystalline polymers are of particular interest for use in MEMS because highly ordered liquid crystalline polymers can be actuated by exposing them to a stimulus (such as heat) that causes a decrease in order, leading to a reversible, macroscopic change in shape. The phase behavior, optical properties, and mechanical properties of planar aligned monoacrylate liquid crystalline polymers with varying crosslinker content are investigated, in order to determine the composition that will yield the largest deformations upon heating. We find that films with the lowest crosslinker content investigated (2.5%) undergo the largest reduction in birefringence as they are heated, corresponding to a loss in order. However, we also observe that the films with the highest crosslinker content investigated (10%) undergo the largest physical deformation upon heating. SEM images illustrating the deformation of liquid crystalline polymer helices as they are heated are also presented.

We developed a novel piezo-driven parallel-kinematics single crystal silicon micropositioning XY stage. This monolithic design features parallelogram four-bar linkages, flexure hinges and piezoelectric stack actuators. The stage is made from single crystal silicon because it has excellent mechanical properties compared to metals, which result in high bandwidth, large work zone and compact size of the stage. Kinematics and dynamics analysis were performed for the design. We also developed microfabrication procedures to make the prototype of the stage. Experiment results show that the mechanical structure of the stage can deliver a 400μm by 400μm square work zone without failing any flexure hinges. With two piezoelectric stack actuators mounted, the stage is able to do open-loop contouring in a 32μm by 32μm work zone with 160V driving voltages applied. The resonation frequencies of the stage are between 1,300 and 1,400Hz.

A number of in-plane spring-like micro-electro-thermal-actuators with large displacements were proposed. The devices take the advantage of the large difference in the thermal expansion coefficients between the conductive arms and the insulator clamping beams. The constraint beams in one type (the spring) of these devices are horizontally positioned to restrict the expansion of the active arms in the x-direction, and to produce a displacement in the y-direction only. In other two types of actuators (the deflector and the contractor), the constraint beams are positioned parallel to the active arms. When the constraint beams are on the inside of the active arms, the actuator produces an outward deflection in the y-direction. When they are on the outside of the active arms, the actuator produces an inward contraction. Analytical model and finite element analysis were used to simulate the performances. It showed that at a constant temperature, analytical model is sufficient to predict the displacement of these devices. The displacements are all proportional to the temperature and the number of the chevron sections. A two-mask process is under development to fabricate these devices, using Si₃N₄ as the insulator beams, and electroplated Ni as the conductive beams.

A Micro Electro Mechanical System (MEMS) for mass detection is presented. It has been developed by the monolithic integration of the mechanical transducer with the CMOS control circuit. The sensor transducer consists on an array of four resonating cantilevers; oscillation is achieved by electrostatic excitation. The independent control on each cantilever of the arrays allows multiple sensing on a single device. The microresonators are fabricated on polysilicon in a compatibilized process with the front-end CMOS circuitry. The readout of the cantilevers oscillation is achieved by a current amplifier. Expected Mass resolution in air is 80 ag/Hz.

The objective of this work is to develop a modeling of a complete smart sensor to be used in a distributed architecture, with the new modeling language, VHDL-AMS. This smart sensor is composed by a sensor or actuator, for example we have used a piezoresistive accelerometer, its signal conditioning module, with both analogue and digital elements, and a bus driver that allows communication with the instrument control device and other sensors. In that way, it is also possible to introduce these microsensors in a distributed architecture that permits communication between microinstruments. This example of modeling through VHDL-AMS shows how this language allows a multitechnological description of a microsystem, including not only electrical signals, but also thermical, kinematic, fluidic, etc. signals. This language also permits to describe systems in different levels of complexity and abstraction, giving the possibility of covering several models from a physical model until a behavioral model, which can be used to obtain a design methodology for MEMS, analogous to the existent design methodology for integrated circuits. The combination of smart sensors models at behavioral level with the microinstrument control circuit models is a first step in the development of a complete design methodology.

In this work, we present a non-linear electromechanical model of an electrostatically excited cantilever that can be used to perform system level electrical simulations. This model is implemented by using an analog hardware description language (VHDL-AMS) that allows its use in a common IC CAD environment like CADENCE. Small-signal and large-signal simulations are performed and the results are compared with a simple linear model (RLC//C) showing the benefits of this model. This model is validated by its fit with the experimental results obtained from a monolithic sub-micrometer cantilever based sensor

A microelectromechanical system (MEMS) merges integrated sensors, microactuators, and low-power electronics. These systems normally have a local sensor communication bus managed by a master node. The purpose of this work is to implement a communication interface that permit connect the integrated MEMS local bus (through the master node) with on a high level microinstrument communication bus. The basic philosophy of this development has been to create an IP model with VHDL for the bus module interface. This interface can be added easily to a microsystem and from of point of view of microinstrument design methodology, MEMS based in this interface module could be easily plugged with the other microsystems on microinstrument architecture. The IP developed is based on the concept of Interface File System (IFS) that contains all relevant information of the microsystem. The use of the IFS in integrated microsystems design permits to insulate its particular characteristics from the whole of microinstrument. Also, this IFS has associated a communication model that allows different views of the system, such as, real-time or command service view, configuration and diagnostic service view. Implementation experiences presented in this paper show that the IFS reduces the complexity of microinstrument applications and make easy the MEMS reuse in other microinstruments. The communication module based on IFS was successfully tested between microsystems based on local sensor bus namely IBIS (Interconnection Bus for Integrated Sensors) and a generic real time microinstrument bus.

The emergence of vertical cavity surface emitting laser (VCSEL) and photo diode (PD) arrays has given scope for the development of many applications such as high speed data communication. Further increase in performance can be obtained by the inclusion of micro-mirrors and microlens in the optical path between these components. However, the lack of efficient assembly and alignment techniques has become bottlenecks for new products. In this paper, we present development of optical sub-assembly and metallic MEMS structures that enable in the massively parallel assembly and alignment of these components to form a single miniature package. VCSEL wafer was processed to have polymer pedestal and polymeric lens on top of it. Such optical sub assembly greatly increases coupling efficiency between the VCSEL and optical fibers. Multiple numbers of suspended MEMS serpentine springs made out of electroplated nickel have been fabricated on ceramic substrates. These springs serve for clamping and alignment of multiple numbers of optoelectronic components. They are designed to be self-aligning with alignment accuracies of less than 3 micron after final assembly. Electrical connection between the bond pads of VCSEL's and PD's to the electrical leads on the substrate has been demonstrated by molten solder inkjet printing into precisely designed MEMS mold structures. This novel massively parallel assembly process is substrate independent and relatively simple process. This technique will provide reliable assembly of optoelectronic components and miniature optical systems in low cost mass production manner.

A novel masking technique that enables the complex patterning of metal on any layer of a released MEMS chip is demonstrated. This technique enables a polysilicon only MEMS process to create low-loss RF devices. To illustrate the advantages of post-release metallization, in a polysilicon only MEMS process, a rotating MEMS tunable capacitor that provides a wide and linear tuning range is presented. The core of the design comes from high yield, mechanically proven gear designs from Sandia’s SUMMiT design library. Significant alterations were made to the gear structure to create the final device. Preliminary tests show device capacitance ratios of 1.8:1, with linear tuning. Increased metal deposition to reduce the device air gap, can produce a capacitance ratio over 6:1.

Utilisation of ultrashort laser pulses enables high precision in laser micromachining processes. Due to low thermal interaction between laser beam and matter, the vicinity of the laser ablation is free from melt and heat influenced zones. Established laser microstructuring processes on basis of femtosecond laser pulses have been applied for manipulation of micromechanical components of Silicon-gyrometers that are manufactured for the automotive industry. Compensation of mechanical imbalance, and adjustment of resonance frequencies have been successfully performed by mass balancing, and manipulation of the spring elements' geometries by laser ablation with a lateral resolution of 10-20 μm, and a vertical resolution of 500 nm-4 μm. The approach for automated laser processing on wafer-level is demonstrated.

Due to their precise focusing properties and the possibility of an excellent non-tactile energy coupling, lasers represent a suitable machining process for miniaturised components of shape memory alloys (SMAs) in micro-system and biomedical technology. SMAs find increasing application in these fields because of their special properties such as super-elasticity and shape memory effect. Current research is concentrated on the development of suitable and economic process strategies for machining micro-components and -actuators using ultra-short-pulse lasers. The application of this laser type enables the realisation of miniaturised components made of SMAs without damaging the grain structure and therefore maintaining the shape memory effect. The processed miniaturised components are characterised with respect to the achieved geometrical resolution, the surface quality of the processed areas and their mechanical functionality. For real production, a reduction of the processing time is necessary. Therefore, different process strategies consisting in different numbers of process cycles (simultaneous material removal and smoothing, material removal and subsequent smoothing) are investigated machining NiTi-components. In this paper, results of the laser based method regarding processing time and surface quality will be presented. In addition, the application of these strategies for the realisation of exemplary actuator or component geometries (e.g. for minimal invasive surgery) will be demonstrated.

We report on methods to minimize thermally-induced deformation in a MEMS-based reconfigurable aperture. The device is an enabling component of the Near-Infrared Spectrometer, a principle instrument on NASA’s James Webb Space Telescope. The Microshutter Array consists of 384x175 individually addressable shutters which can be magnetically rotated 90° into the plane of the array and electrostatically latched open. Each shutter is a 100x200 μm rectangular membrane suspended by a small neck region and torsion flexure. The primary materials in the shutter are a 5000Å Si3N4 layer for mechanical rigidity, 2000Å Al for opacity and electrostatic latching, and 2200Å Co90Fe10 for magnetic actuation. This multi-layer stack presents a challenge due to the operating temperatures required for the device: both room temperature (300K) and cryogenic temperature (30K). Thermal expansion of the materials causes the shutters to bow out of plane excessively, which can prevent actuation of the shutters, cause damage to portions of the array, and allow light leakage around closed shutters. Here we present our investigation of several methods to prevent microshutter bowing including deposition of additional materials on the shutters to create a symmetrical layer stack and replacing the current stack with low-coefficient of thermal expansion materials. Using shutter-size suspended cantilever beams as a rapid-development test bed, we have reduced out-of-plane bowing between 300K and 30K to 10% or better. We are currently applying these results to microshutter arrays to develop shutters that remain flat from room temperature to cryogenic temperature while retaining the required mechanical, optical, and magnetic properties.

Wafer bonding became a key technology in various MEMS devices manufacturing. In this respect, wafer bonding is a very important technology as far as it enables not only 3D structure building but also wafer level packaging. Plasma activated wafer bonding is a surface activation method in which by applying a plasma treatment to the wafers prior to bringing them in contact for bonding, the surface chemistry can be tailored in order to obtain maximum bond strength for low temperature thermal annealing. A major advantage of this process is that it makes possible some bonding applications which are not possible using standard bonding processes due to different materials characteristics (e.g. high thermal mismatch of the two bonding partners, low Tg for polymer bonds, etc.) Plasma activated bonding was successfully applied for different types of materials: silicon, compound semiconductors, oxides and polymers (e.g. PMMA). The present paper presents experimental results demonstrating the benefits of this new technology and shows examples on how plasma activated wafer bonding can be an alternative to standard wafer bonding processes.

NASA's planetary exploration strategy is primarily targeted to the detection of extant or extinct signs of life. Thus, the agency is moving towards more in-situ landed missions as evidenced by the recent, successful demonstration of twin Mars Exploration Rovers. Also, future robotic exploration platforms are expected to evolve towards sophisticated analytical laboratories composed of multi-instrument suites. MEMS technology is very attractive for in-situ planetary exploration because of the promise of a diverse and capable set of advanced, low mass and low-power devices and instruments. At JPL, we are exploiting this diversity of MEMS for the development of a new class of miniaturized instruments for planetary exploration. In particular, two examples of this approach are the development of an Electron Luminescence X-ray Spectrometer (ELXS), and a Force-Detected Nuclear Magnetic Resonance (FDNMR) Spectrometer. The ELXS is a compact (< 1 kg) electron-beam based microinstrument that can determine the chemical composition of samples in air via electron-excited x-ray fluorescence and cathodoluminescence. The enabling technology is a 200-nm-thick, MEMS-fabricated silicon nitride membrane that encapsulates the evacuated electron column while yet being thin enough to allow electron transmission into the ambient atmosphere. The MEMS FDNMR spectrometer, at 2-mm diameter, will be the smallest NMR spectrometer in the world. The significant innovation in this technology is the ability to immerse the sample in a homogenous, uniform magnetic field required for high-resolution NMR spectroscopy. The NMR signal is detected using the principle of modulated dipole-dipole interaction between the sample's nuclear magnetic moment and a 60-micron-diameter detector magnet. Finally, the future development path for both of these technologies, culminating ultimately in infusion into space missions, is discussed.

The design and fabrication of micro gratings and polarization beam splitters for potential use in micro optical pickups are presented. Silicon nitride is used as the optical material for its low absorption in the visible wavelength. The micro components are framed by a pop-up poly-silicon mechanism as in the standard surface micromachining technology. The micro grating is a binary phase grating. The diffraction ratio between 4 and 10 can be achieved provided that the duty cycle is between 0.4 and 0.6 and the depth between 455nm and 485nm. For a grating designed for a diffraction ratio of 7, the measured ratio is 8.31.The polarizing beam splitter is a silicon nitride thin film placed at the Brewster angle. The transmittance of the TM mode of a micro polarization beam splitter was measured to be more than 98.50%.

Mechanical characterization is vital for the design of MEMS/NEMS. Many methods have been developed to measure the mechanical properties of materials; however, most of them are either too complicated, or expensive for industrial application, or not accurate. This paper describes a new characterization method to extract the mechanical properties of the materials that is simple, inexpensive and applicable to a wide range of materials. The beams of the material under tests, are patterned by laser micromachining and released by KOH etch. Surface profilometer is used to scan along μ-machined cantilevers and produce a bending profile, from which the Young’s modulus can be extracted. The errors due to initial curling and anticlastic (width) effect have been carefully studied. A new ANSYS FEA model is developed to evaluate the effects and test structure designs. SiN_x, Ni, SiC and nanocrystal diamond cantilevers have been fabricated and their mechanical properties, e.g. Young’s modulus have been evaluated as 154+/-12GPa, 202+/-16GPa, 360+/-50GPa and 504+/-50GPa, respectively. These results are consistent with those measured by nano-indentation. Residual stress gradient has also been extracted by surface profilometer, which is comparable with the results inferred from Zygo interferometer measurements. It is also possible to extract plate modulus and Poisson ratio with minimal error achieved. This method can be extended to AFM or nanometer-stylus profilometer for NEMS mechanical characterization.

Detecting quantum fluctuations of a mechanical resonator is a long-standing goal of experimental physics. Recent progress has been focussed on high frequency (MHz to GHz) resonators inserted in a milli-Kelvin environment, with motion detection performed by single electron transistor means. Here we propose a novel experimental approach based on high-sensitivity optical monitoring of the displacement of the resonator and feedback cooling. The experimental setup is based on a micro-mechanical resonator inserted in a high-finesse optical cavity and monitored by a highly-stabilized laser system. Available optical technologies provide an unequalled sensitivity, in the 1E-20 m/sqrt{Hz} range. The displacement signal is used in real-time to perform a feedback cooling in order to set the resonator's fundamental mode of vibration in its quantum ground state. With the resonator at cryogenic temperature, the feedback cooling mechanism should allow to reach an effective temperature in the micro-Kelvin range.

The paper deals with a very high sensitive integrated humidity sensor compatible with CMOS technology. This sensor is a polysilicon Suspended Gate Thin Film Transistor (SGTFT), fabricated using a low temperature surface micromachining process. Microtechnology technics using sacrificial layer are used to fabricate polysilicon bridge which acts as the transistor gate. Transistors are characterized at various humidity rates and transfer characteristics show highly sensitive dependence with humidity. The small air-gap (0.5 μm) between the gate and the channel explains the amplifying effect of the sensitivity: threshold voltage shift is more than 17V when the humidity ratio varies from 20 to 70%.

A micro component for a non-selective NDIR (non dispersive infrared) gas detection system is presented in this work. This device consist of an IR detection module composed of a thermopile and a thin film filter array. The thermopile arrays (up to 4x4) are built on a silicon substrate by bulk micro-machining processes. The whole matrix is built on a thin freestanding silicon oxide/silicon nitride membrane of 2100x2100μm2 defined by anisotropic wet etching. To ensure the existence of hot and cold junctions for each detector we define on the insulating membrane absorbers and ribs, 6μm thick, by heavy boron doping of the silicon underneath. The ribs crisscross the membrane contacting the silicon bulk acting as a heat sink. Absorbers are located in the centre of each individual pseudo-membrane defined by the ribs intersection. Incident radiation heats up the absorber creating a temperature difference that is measured by the thermocouples that are placed between the absorber and the ribs. On a second chip, the elements of the filter array are fabricated in a matching configuration. The filters are built on a silicon substrate alternating thin films of different refraction index acting like a Fabry-Perot structure with 2-8μm silicon oxide cores. The transmitted filter peaks are not tuned for the detection of any specific substance: they configure a non selective general purpose filter array (400-4000 cm^-1), making signal processing and pattern recognition techniques necessary. Both dies have been fabricated and characterized and have been successfully attached using flip-chip techniques. The measurements on these devices have been used to build an optical simulation tool that allows the assessment of the whole NDIR system behaviour in operating conditions.

In this work a thin film gas microsensor based on both a double polysilicon micro-hotplate (MHP) and a polysilicon floating gate MIS transistor (FG-MIS) is described. Sensing section is a squared polysilicon plate which contains a doped Zinc Oxide (ZnO) thin film. The sensing section is heated by an U-shaped polysilicon stripe which is electrically isolated from the top and the bottom using oxide films. The micro-hotplate is both mechanically supported and thermally isolated using a deep cavity micromachined in the silicon substrate. The sensing film is electrically connected to the floating-gate transistor where the conductivity channel is modulated by the charged generated at the sensing film. The sensor structure was characterized for detecting carbon monoxide (CO) at 300 °C. The hot area is thermally isolated using an arrangement of cavities micromachined in the silicon substrate. Finally a complete layout of the sensor system is presented in this paper.

The aim of this work is the fabrication of a cheap sol-gel Pt-doped TiO₂ thin film sensor on silicon substrate, evaluate electrical performances of electrical interconnections and responses of sensitive film in severe environment like exhaust of combustion process. The sensor will be implemented as microsensors for NOx or oxygen detection, while a preliminary investigation on real operative conditions shows that the transducers perform a response time (t₉₀) in real condition smaller than 1 second at 600 °C. Application field of this type of transducer will be evaluated in a real spark ignition engine, to monitor air/fuel ratio and also monitoring the combustion quality in other industrial combustion processes like domestic heating systems. The production process of this devices, and particularly thin film deposition, can be carried out on a 3" silicon wafer and obtaining with a single batch process more than 300 sensors for wafer, 2x2 mm². The sensors are provided with an integrated heater and a thermometer to perform temperature compensation. Actually this work try to develop an affordable process to integrate cheap sol-gel deposition process with silicon technology; a particular study is devoted to a complete photolithographic patterning of titania sensitive film, that is very difficult to etch after complete annealing, in order to have sensitive film only onto well defined areas of wafer. Same process, with little modification, can be applied to different kind of sensitive film, pure and doped ones. Different strategies on protective coating were evaluated to reduce electrical contacts degradation at high temperatures, obtaining long time stability of overall microsensor.

In this work we report on the development of biochips for the rapid analysis of single cells and other particles. We have developed a device that can simultaneously measure the optical and electrical properties of single cells or other micron-scale particles. The micro flow-cytometer chip consists of a planar electrode array onto which a micro-fluidic channel is fabricated from polyimide. The electrodes are used to measure the impedance of single cells flowing through the channel at hundreds per second. The impedance of single particles is simultaneously measured at typically two separate frequencies (e.g. 0.5MHz and 2MHz) using a lock-in system and high specification instrumentation amplifiers mounted on top of the micro-fluidic chip. The impedance data provides information on the membrane characteristics of cells and also the size of the particle. In addition a three-wavelength confocal optical system has been developed which is used to simultaneously interrogate the optical properties of particles. The device can detect small numbers of fluorescently labelled rare particles in a sample and has been used for the analysis of blood and suspensions of latex beads.

The objective of this ongoing work is the development of a microlab on flexible tag, capable to monitor the quality of the food, during transport, storage and vending. The idea is to bring together different sensor technologies that will be integrated into a data communication environment for online food monitoring during the logistics chain. The proposed solution is the concept of silicon chips and microcomponents assembled and integrated on top of a flexible substrate acting mainly as a passive interconnect structure. Three technologies have been identified as necessary to get the final integration: a) Substrate technology. This technology refers to the realisation of the flexible substrate with the metallic interconnections. b) Assembly technology to integrate the discrete components on the flexible substrate. The conventional processes are wire bonding, flip chip, and adhesive bonding. c) Encapsulation technology and windows opening over the gas sensitive areas. The first flexible tag prototype integrates two different metal oxide sensor arrays with a commercial microprocessor. The dimensions are 43 mm long, 22 mm wide and about 2 mm thick and two metal levels are necessary for the interconnect. The strategy undertaken by the groups involved in this work, consists in the evaluation of different approaches, that combine diverse process sequences and materials, with the final aim of identifying the best solution. Regarding the substrate technology, the approach realized using Pyralux copper-clad laminated composites, constructed of DuPont Kapton polyimide film with copper foil on both sides, as flexible substrate will be described in this paper. The cupper interconnections are generated by standard photolithography and wet etching and the vias definition in Kapton is performed by femtosecond laser ablation. On the other hand, the assembly technology based on the use of anisotropically conductive adhesives will be also illustrated.

In this paper, we present both a theoretical evaluation and the fabrication of a novel polymerase chain reaction (PCR) microdevice. This microdevice contains elements for both thermal cycling and fluorescence detection. The proposed device is composed of a reaction chamber with integrated temperature sensor, heaters, p-n diode and optical filter. The advantage of combining these in a single structure is that real time detection of DNA amplification will be possible using a small volume of the PCR solution. The photodiode is covered by a thin film optical filter in order to block out the light which is used to excite the fluorophore dyes. CdS is used for the first time for such a filter and the complete micro-fabrication process is described.

Fabrication of surface-micromachined structures by a post-processing module above standard IC circuits is an efficient way to produce monolithic microsystems, allowing nearly independent optimization of the circuitry and the MEMS process. However, until now the high-temperature steps needed for deposition of poly-Si have limited its application. SiGeM explores the possibilities offered by the low-temperature (450°C) deposition and structuring of poly-SiGe layers, which is compatible with the temperature budget of fully-processed standard IC wafers. In the SiGeM project several low-temperature deposition methods (CVD, PECVD, LPCVD) were developed, and were evaluated with respect to growth rate and material quality. The interconnection technology to the underlying CMOS circuitry was also developed. The capabilities of this new integration technology will be demonstrated in a monolithic high-performance rate-of-turn sensor, currently considered the most demanding MEMs application in terms of material properties of the structural layer (thickness > 10mm, stress gradient < 0.3MPa/mm) and signal processing circuitry (capacitance resolution in the aF range, SNR > 110 dB). System partitioning will combine analog and DSP circuit techniques to maximize resolution and stability. Parasitic electrical coupling within different parts of the system has been analyzed, and countermeasures to reduce it have been incorporated in the design. The feasibility of the approach has already been proved by preliminary characterization of working prototypes containing released microstructures deposited on top of preamplifier circuits built on a 0.35mm, 5-metal, 2-poly, standard CMOS process from Philips Semiconductors. Resonance frequencies are in good agreement with predictions, and quality factors above 8000 have been obtained at pressures of 0.8 mTorr. Measured SNR confirms the capability to achieve a resolution of 0.015°/s over a bandwidth of 50 Hz.

Laser micromachining techniques are among the most promising fabrication processes in strategic industrial fields. Although lasers systems have been widely applied last twenty years in semiconductor industry for microfabrication process development, the current availability of new excimer and Diode Pumped Solid State Lasers (DPSS) sources are extending the applications fields of laser microprocessing. Nowadays MEMs, fluidic devices, advanced sensors and biomedical devices and instruments are among the more promising developments of this technology. Nevertheless the fast progress of this technology has brought as a consequence the building up of specific laser based machines for each process of interest (most of them until now strictly 2D), and an important gap has been generated, from the fabrication point of view, in fully 3D potential applications. In this work, the conception, design and first results of a fully automatized 3D laser micromachining workstation, based on the main concept of flexibility, is presented. This system integrates two UV laser sources, excimer and DPSS in ns pulse regime, and an advanced positioning system (with six degrees of freedom) for complex parts machining. Several examples of first results obtained with this system, including processing of semiconductors for sensoring and photovoltaic applications, organic materials for biomedical devices and metallic materials for different strategic industrial sectors are presented.

MEMS fabrication processes are characterized by a numerous useable process steps, materials and effects to fabricate the intended microstructure. Up to now CAD support in this domain concentrates mainly on the structural design (e.g. simulation programs on FEM basis). These tools often assume fixed interfaces to fabrication process like material parameters or design rules. Taking into account that MEMS design requires concurrently structural design (defining the lateral 2-dim shapes) as well as process design (responsible for the third dimension) it turns out that technology interfaces consisting only of sets of static data are no longer sufficient. For successful design flows in these areas it is necessary to incorporate a higher degree of process related data. A broader interface between process configuration on the one side and the application design on the other side seems to be needed. This paper proposes a novel approach. A process management system is introduced. It allows the specification of processes for specific applications. The system is based on a dedicated database environment that is able to store and manage all process related design constraints linked to the fabrication process data itself. The interdependencies between application specific processes and all stages of the design flow will be discussed and the complete software system PRINCE will be introduced meeting the requirements of this new approach. Based on a concurrent design methodology presented in the beginning of this paper, a system is presented that supports application specific process design. The paper will highlight the incorporated tools and the present status of the software system. A complete configuration of an Si-thin film process example will demonstrate the usage of PRINCE.

This paper presents the whole process of building up a high precision, high dynamical MEMS acceleration sensor. The first samples have achieved a resolution of better than 500 ug and a bandwidth of more than 200 Hz. The sensor fabrication technology is shortly covered in the paper. A theoretical model is built from the physical principles of the complete sensor system, consisting of the MEMS sensor, the charge amplifier and the PWM driver for the sensor element. The mathematical modeling also covers problems during startup. A reduced order model of the entire system is used to design a robust control with the Mixed-Sensitivity H-infinity Approach. Since the system has an unstable pole, imposed by the electrostatic field and time delay, caused by A/D-D/A conversation delay and DSP computing time, limitations for the control design are given. The theoretical model might be inaccurate or lacks of completeness, because the parameters for the theoretical model building vary from sample to sample or might be not known. A new identification scheme for open or closed-loop operation is deployed to obtain directly from the samples the parameters of the mechanical system and the voltage dependent gains. The focus of this paper is the complete system development and identification process including practical tests in a DSP TI-TMS320C3000 environment.

This paper describes the application of a micromachined resonator to verify the vacuum pressure and sealing of cavities in micromechanical components. We use an electrostatic driven and capacitively sensed bulk silicon resonator fabricated by Bonding and Deep Reactive Ion Etching (BDRIE) technology. The resonator operates at the first fundamental frequency. The damping is used as a degree of the pressure. Transversal comb structures act as squeeze film damping sources. Post-processing gap reduction substructures are used to increase the damping in the vacuum pressure range. This method makes it possible to observe the pressure over the time of smallest gas volumes by monitoring the damping of integrated micro mechanical resonant structures. Therewith it is possible to estimate the hermetic sealing quality of the closed sensor package. A transfer curve with a logarithmic characteristic is measured.

This paper discusses the design and testing of a new velocity sensor, designed to be used in combination with a piezoelectric patch actuator to form a closely located sensor-actuator pair for the implementation of active damping. The velocity sensor consists of a principal spring-mass seismic sensor with an embedded direct velocity feedback control loop. This internal feedback loop uses a control spring-mass seismic sensor and a reactive actuator which are fixed on the seismic mass of the principal sensor. The control gain is tuned to obtain two effects: first the output signal from the principal sensor becomes directly proportional to the base of the sensor itself and second, the fundamental resonance of the principal seismic sensor is cut down by the active damping effect of the internal loop. The background concepts of this sensor are first reviewed. The practical feasibility is then studied considering a prototype model. The stability of the internal feedback control loop has been assessed first. Following this, the frequency response function of the sensor without and with the internal feedback loop has been measured. The experimental measurements have shown that the internal feedback loop is conditionally stable but guarantees enough gain margins in order get the necessary control action to obtain the desired velocity output from the sensor. The sensor has been successfully tested with a closed loop, and shows the desired velocity output with no resonance at the fundamental natural frequency of the seismic sensor.

A novel pressure sensor based on a Suspended Gate MOSFET is presented. The SG-MOSFET structure, fabricated in a SOI wafer, is modified by etching the bulk of the wafer back side in order to create a thin clamped membrane and to be able to measure pressure displacements. The whole structure forms a diaphragm, in which the bottom plate is a pressure sensitive terminal and the top plate forms the MOSFET gate terminal where the air-gap is proportional to the pressure application as gate insulator. The change of this air-gap distance modifies the drain current of the sensing MOSFET. The gate is suspended by arms allowing to modify the sensitivity of this sensor by a drive voltage. Two operation modes are proposed, one uses the drain current variations as output signal and the second one take advantage of the snap down effect. A model along with Finite Element Method simulations were made to provide a design model for the pressure sensor. Some pressure sensors were been fabricated with different dimensions.

This paper reports a new method of amorphous layer deposition thanks traditional PECVD insulators equipments for seed layer performing. The main application of this method is the realisation of seed layer for EPIPOLY process without using LPCVD furnace. Amorphous layers are obtained thanks to traditional PECVD insulators equipment, AMT 5000, which allows to prevent LPCVD furnace from cross contamination. Furthermore AMT 5000 as single wafer equipment fits much better in ato research using. The major interest of the method is its compatibility with traditional microelectronic process and it involves very common PECVD equipment.

Nanocrystalline Bi₄Ti₃O₁₂ (BTO) thin film pressure sensor was fabricated by sol gel method. The multiple Bi-Ti-O layers were spin coated over the TiO₂ buffered Si/SiO₂/RuO₂ substrate, followed by heating of each layer at 300 °C for 15 mins. The nanocrystalline Bi₄Ti₃O₁₂ film was formed after the sample was rapid thermal annealed at 450 °C in air for 60 s. The scanning electron microscope result showed that the film exhibited crack free, fine and uniform grain structure, where the grain size obtained was around 10 to 15 nm. For the sensor response measurement, Al film was deposited as top electrode and the sensor tested by pneumatic loading method. The nanocrystalline Bi₄Ti₃O₁₂ (BTO) thin film demonstrated good repeatability for the pressure sensing. The sensor achieved a linear characteristic response between 17.5 psi and 65 psi with sensitivity of 0.3 mV / psi.

Three types of micropumps based on TiNi shape memory alloy thin films were designed and fabricated. The TiNi films were prepared on silicon substrate by co-sputtering TiNi target and a separate Ti target at room temperature, and then post annealed at 650°C. The first pump design is based on a single TiNi/Si bimorph membrane structure with inlet and outlet. The second design is based on three layer structures bonded together, with one TiNi/Si active membrane structure and two layers of check valves. The third design is based on two TiNi/SU-8 composite structures, with TiNi as an actuation element, and SU-8/Si as a spring-back structure. The three types of micropump structures were fabricated based on the conventional MEMS processes.

Hydrodynamic focusing of flows can be used for a variety of applications. This paper presents the design of a microdevice that performs 3D hydrodynamic flow focusing, with the advantage of being capable to be integrated into bidimensional arrays. The device is formed by two structures that conduct different fluids from different inlet ports to a common outlet. Near the outlet, a three-dimensional structure is built that performs the focusing of one fluid inside the other one. The device is built on silicon substrates. The paper describes the fabrication process in detail, and some preliminary tests made on a prototype are presented. Numerical simulations of the fluidic behavior are also discussed.

Micromachined microsensors for gas or flow detection based on physical behaviour of a special layer of a membrane have to fulfil high quality and reliability requirements especially in safety or security applications. For the reliability assessment a combination of simulative and experimental methods is usually carried out for the fully understanding of the thermo-mechanical behaviour. Due to the micromachining involved in the production of the sensor components the thermo-mechanical response of the layers are strongly dependent on process parameters. Therefore experimental methods for the 3D deformation detection are essential. In this paper experimental methods such as profilometry and scanning probe microscopy are tested for the evaluation of residual stresses and thermomechanical induced stress/strain fields.

The control and handling of fluids and fluid-based samples is central to the majority of applications in the areas of Micro Analysis systems and the Lab-on-a-chip. As a result, there is a great deal of research and industrial interest in developing specific technologies for this purpose: micropumps, micromixers, microstirrers, etc. One widely used technology in these systems is electrokinetics, the use of electric fields for the manipulation and control of fluids and particles. In DC electrokinetic systems, high voltages (typically ~1kV) are required for controlled manipulation and separation. The use of AC electric fields presents a range of different potential applications as well as the potential for better integration into microsystems. AC Electrokinetic devices for the handling of fluid require significantly lower voltages (~10V) and therefore a four order of magnitude reduction in power requirements. This paper presents devices based on AC electroosmosis and Electrothermal Electrohydrodynamics. The first mechanism involves the interaction of the Electrical Double Layer induced on electrodes by an applied potential and the electric field generated by the same potential. The second involves the interaction of an electric field with gradients in polarisability of the fluid produced by non-uniform heating. Several different designs are presented with applications in pumping, mixing and the general area of micro AC electric field microfluidic control. A specific example is presented: the use of the technique for the local modification of streamlines and deflection of fluids is presented and applications to analysis and sensing are discussed.

This paper presents a new device for the pH detection. It is based on a suspended polysilicon gate field effect transistor (SGFET). The sensitive layer is made of silicon nitride as for ISFET technology. The suspended bridge, used as gate electrode, is formed with doped polysilicon covered with silicon nitride layers for electrical insulation. The layers are deposited by Low Pressure Chemical Vapor Deposition (LPCVD). Surface micro-technology allows to obtain a small height (0.5μm) suspended-bridge. In this case, the solution penetrates under the gate. The high field effect in the gap between the gate and the channel is enough to change the charges distribution. Very high pH sensitivity, greater than 200 mV/pH, is found with this new structure and it is much higher than the usual Nernstian sensitivity of ISFETs. The device concept, electrical characteristics, and the effect of the thickness of the gap between the bridge and the sensitive layer on the pH sensitivity are discussed in this study.

In order to compare their gas sensing properties two kinds of sensors based on silicon cantilevers of similar characteristics have been fabricated: On one side we fabricated gravimetric gas sensors based on silicon cantilevers acting as resonators. The active layers consisted of polymer films deposited on top of the cantilevers. Sensors were maintained oscillating at their natural resonance frequency with electronic circuitry also developed in this work. Basically they consist of mass-spring mechanical resonators in which the mass increment due to gas sorption in the polymer provokes a shift on the resonance frequency. The output signal is a sinusoidal voltage extracted directly from the oscillator, and the amount of gas absorbed is related to the frequency of this output signal. The second type of sensors consisted of capacitors in which one electrode is a silicon cantilever and the other is a fixed metallic electrode fabricated parallel to the silicon cantilever. The silicon cantilever of these devices is covered with the same polymer films as for the resonators. The sensing principle in this case relies on the bending produced by the internal mechanical stress induced by the absorption of the gas in the polymeric layer. In these devices the signal is obtained by measuring the capacitance between the two plates of the capacitor, in this case the out coming signal was the current of the capacitor: an amplitude modulated signal. The gas response of both types of sensors have been characterized and a comparison is presented in this paper.

Precise and continuous ethylene detection is needed in various fruit storage applications. The aim of this work is the development of a miniaturised mid-infrared filter spectrometer for ethylene detection at 10.6 μm wavelength. For this reason optical components and signal processing electronics need to be developed, tested and integrated in a compact measurement system. The present article describes the proposed system set-up, the status of the development of component prototypes and results of gas measurements performed using a first system set-up. Next to a microstructured IR-emitter, a miniaturised multi-reflection cell and a thermopile-array with integrated optical filters and microstructured Fresnel lenses for the measurement of ethylene, two interfering gases and one reference channel are proposed. Recently a miniaturised White cell as absorption path is tested with various commercial and a self-developed thermal emitter. First ethylene measurements have been performed with commercial twofold thermopile detectors and a Lock-in-amplifier. These showed significant absorption at an ethylene concentration of 100ppm. For the detection module different types of thermopiles were tested, first prototypes of Fresnel lenses have been fabricated and characterised and the parameters of the optical filters were specified. Furthermore a compact system electronics for signal processing containing a preamplification stage and Lock-in-technique is in development.

This paper reports the fabrication of an optical receptor for cyclohexane vapour using self-assembly monolayer (SAM) of 1-amino, 9-fluorenone compound. The SAM was built up on quartz substrate and quartz substrate-coated monolayer Langmuir-Blodgett (LB) film of arachidic acid. The UV-VIS spectroscopy technique was used to characterize the self-assembled film. It was found that the SAM on the quartz-coated LB film indicated a clearer optical absorption profile than the SAM on the quartz surface. The optical sensing characteristic of the SAM to the presence of the saturated vapour of cyclohexane indicated that the thin film features a good sensing sensitivity.

We report, for the first time, the design and simulation of electrostatic MEMS comb-drive actuators incorporating gray-scale technology to tailor actuator properties. Specifically, 3-dimensional comb-fingers and suspensions enable customized displacement characteristics and lower driving voltages without increasing the device footprint. The local height of each comb-finger is varied using gray-scale technology to modify the change in capacitance with position, thereby altering the generated force. The displacement characteristics of various comb-finger geometries were simulated using analytical approximations and finite element analysis (FEMLAB). Simulations show that variable height comb-finger designs may reduce the local change in capacitance (or force) by up to 75%, resulting in increased displacement resolution. We also show that gray-scale technology is capable of simultaneously reducing the height of comb-drive suspensions, causing a corresponding reduction in spring constant for lower driving voltages. The design and simulation of variable height comb-drives is presented along with experimental confirmation of the simulated performance.

Soft conducting polymers working in aqueous solutions were the bases for the development of electrochemomechanical actuators. The actuation of those devices involves: polymers, counterions, water, electric pulses and volume variations by water and counterions interchange with the polymer. Those processes mimic similar ones occurring in natural muscles, being the origin of their nomination as artificial muscles. The driving force for the stimulation of the processes is electric pulses generating electrochemical reactions. This fact gives a unique possibility to these actuators: they can work, simultaneously, as an actuator driven by a constant current and as a sensor of any chemical, mechanical or physical variable influencing the electrochemical reaction. We will show here how, using only two connecting wires, those devices work, simultaneously, as both, actuators and as a mechanical and a chemical sensor.

This paper presents a thermopneumatic actuator to build large tactile displays as well as a smart activation circuitry to study and improve its performance. Since the main drawback of large tactile screens in the market is their cost, this proposal is intended to reduce the price because of the simplicity of the actuator and the potential low cost assembling. A small display with 4 x 4 taxels and 2.54mm of distance between centres has been built to show the viability of the proposal. Furthermore, a smart actuation strategy is implemented where the heater element (a diode) is also used as sensor in a feedback control loop that improves the dynamic response. Such strategy consists in sensing the voltage drop in the diode to measure its temperature, thus it can be heated up quickly without being destroyed because power supply is decreased once the target temperature is reached. We have measured rise times around 2 seconds and fall times around 4 seconds, while the maximum force and stroke are above 10grams (0.1N) and 1mm respectively. The obtained results are good, specially to implement a large tactile screen. Power consumption is high, but it could be lower if latching mechanisms are used to keep the taxel active without power supply.

We present polymeric MEMS materials which reversibly respond to either thermal or UV stimuli by moving between nearly flat (r ~ infinity) and tightly curled states (r ~ 5mm) with variations in the radiation environment or temperature. The molecular orientation gradient of a liquid crystal network controls the primary bending axes, while controlled order parameter variations are responsible for the degree of deformation. In the case of thermal activation, these order changes are dominated by thermal motion, while UV-switchable defects bring about reduced network order in the case of UV actuation. We report fabrication and operation of the actuators and supplementary data regarding alignment configurations for controllable deformations, the phase behaviour of the liquid crystal constituents, thermal expansions, and absorption of the UV dyes are included. We find that splayed molecular configurations are preferred over twisted modes due to their single deformation axis, and that the optimum concentration of active molecules for UV-driven actuation is on the order of 7-8wt.%.

Miniaturization, low cost and excellent performances at microwave and millimeterwave applications represent the main leitmotivs of the future mass market communication systems. Consequently, a novel "MEMS above IC" technology has developed in order to allow the elaboration of post-processed micro-machined passive components on top of SiGe circuits to realize a complete short-range communication receiver centered at 24 GHz. The developed technology is based on the use of : -a thick organic layer (BCB), which is employed as a dielectric membrane, -metallizations to realize the passive metal layer and also the vias to interconnect the active circuits with the post-processed passive components, -and a bulk silicon micromachining. This 'above IC' technology presents many advantages, as it uses conventional equipments of microelectronics and is in adequation with high frequency applications. A specific attention has been carried out in order to assure the compatibility of the post-process steps and the IC’s. This has been performed through the choice of the adequate technological steps, which had to present a low temperature budget. The compatibility of each step has been evaluated with a specific test protocol on SiGe transistors. It implies static and dynamic characterisation of these transistors as well as low frequency noise measurements. Each step has been validated, even the bulk silicon micromachining. Design rules have thus been defined in order to localize the silicon etching without any damage on the ICs.

A new structure for micro-machined piezoelectric mechanical filters with high-Q is presented. The structure is composed of two silicon cantilevers which have thin film PZT transducers deposited on top of each and are mechanically connected together by a silicon linkage. A model is proposed in which finite element analysis (FEA) is combined with a two-port microwave network representation to show high-Q characteristics. Using the model, key parameters in the design include the substrate thickness, and the position, length and width of the linkage, and the effect of these on filter performance, including the resonant frequencies of the in-phase and out-of-phase vibrational modes, bandwidth, quality factor (Q), insertion loss and ripple are also investigated. The results show that the coupling produces additional resonances compared with ladder type filters composed of uncoupled cantilevers, and a significant increase in Q of about a few hundred times higher with correct design, than uncoupled cantilevers.

An argument for the geometry based frequency range extension of tunable MEMS capacitors is presented. It is shown that, besides reducing the length of the feed arms, the parasitic inductances in a parallel-plate MEMS capacitor can be reduced further by optimising the plate geometry. Extension of the self resonance frequency is demonstrated with reduced circumference of the plate, due to high-frequency currents travelling around the edge of the plate and acting as a major component affecting the self-resonance frequency (SRF) of the capacitor. Full-wave 2.5-D electromagnetic simulation results using Agilent EEsof's ADS Momentum are presented that demonstrate the improvement in self-resonance frequency of circular and symmetrically fed structures. It is shown that efforts in shortening current paths by means of slots did not yield significant further improvement.

We present an original RF-MEMS switch topology associated with an efficient design methodology. The proposed switch has been optimized thank to a scalable electrical model, fabricated and measured and exhibits isolations better than -23 dB and losses less than 0.25 dB at 24 GHz for a pull down voltage of 22V. The proposed topology and design methodology can then be efficiently used to optimize more complex RF-MEMS with enhanced microwave performances.

There are several micro sized thermal emitters commercially available, but compared with an ideal black body radiator, their emissivity and thus the emitted radiation is moderate. This was the motivation to develop a novel type of micromachined thermal IR-emitters. The main difference compared with common thermal micro emitters is the use of 2D structured bulk silicon. The regular ordered macropores of the emitters are obtained by electrochemical etching of prepatterend silicon substrates. Typical pore diameter of the fabricated photonic-crystal-like structures are in the range of 2.5 μm to 30 μm. The macroporous silicon shows a black-body-like emission profile for a wide wavelength range.

Multimode microbolometers for wavelength-selective infrared detection have been designed using a Genetic Algorithm and an electromagnetic model of the planar antenna. Wavelength selectivity can be varied by changing the distance to a tuning mirror, or by changing only lithographically drawn parameters, with bandwidth narrower than Fabry-Perot microbolometers. The design of a three color system covering the 7-14 micron band is presented.

This paper presents the design and development of a safe MEMS based micro electro-thermal igniter for a safe microfuze for military purpose. The proposed device’s architecture is made of: (1) one pyrotechnical micro igniter, (2) one arming function, (3) one disarming function and (3) one sterilization function. The pyrotechnical electro-thermal igniter consists in a resistive element that converts electrical energy into heat to initiate an energetic material. The arming function permits the igniter to be armed, ready to fire, only if the ignition conditions are respected. For that, a short-circuit to the electrical ground is cut and the igniter is connected to the power supply. The igniter can be reset to the safe mode (disarmed state) thanks to the disarming function that reconnects the igniter's electrical pads to the electrical ground. If necessary the igniter can be sterilized meaning that the system's ignition capability is definitively removed. All these functions are based on the use of two electro-thermal micro switches : one ON-OFF and one OFF-ON. Due to the application requirements (the fuze is used once but after a long storage, all components must have a high level of safety and reliability and the power consumption must be minimized), we opted for a new generation of one shot, safe and reliable micro switches. They are based on electro thermal mechanisms and consist in breaking one electrical connection (ON-OFF switch) or micro soldering locally two electrical connections (OFF-ON switch). Both switches have been developed in MEMS technology, characterized and are presented in this paper. A prototype of safe micro igniter with ON-OFF and OFF-ON switches has been also realized and is presented.

This paper presents a wearable human movement monitor designed within the context of a telehealthcare system for the elderly. One major characteristic of this device is the capability for an on-line personalization to the user. This capability compels to a trade-off among processing capacity, portability, low cost and power consumption, which are necessary to assure its feasibility. We have performed a preliminary laboratory study to assess the influence of the customization capacity in the reliability of the device for capturing falling events. The study was based carried out over 8 voluntaries and demonstrated that the device is able to distinguish true falling events from normal activities like fast walking or going up/downstairs. Moreover, our outcomes indicate that the subject and the environment have a critical influence on the reliability of the falling detection. This result underlines the importance of providing personalized support in telehealthcare.

This paper presents a wireless sensor network for smart electronic shirts. This allows the monitoring of individual biomedical data, such the cardio-respiratory function. The solution chosen to transmit the body's measured signals for further processing was the use of a wireless link, working at the 2.4 GHz ISM band. A radio-frequency transceiver chip was designed in a UMC RF 0.18 μm CMOS process. The power supply of the transceiver is 1.8 V. Simulations show a power consumption of 12.9 mW. Innovative topics concerning efficient power management was taken into account during the design of the transceiver.

The aim of this article is to illustrate the need for reverse engineering in order to manufacture parts for Micro- and Nano- electromechanical systems, specially in the medical field. Afterwards, an overview of the newest optical devices for production metrology and quality control of Mems & Nems is provided. Finally, a new concept for a modular optical-system able to digitalise micro-parts is presented. The system is proposed for scanning measurement of topographies and digitalising of complete geometries. The system is able to generate a parametric 3D database that can be used for tooling or design modifications. The resulting data can also be used to generate a colour map comparison report. This paper ends with conclusions and an overview of the future in metrology for Mems & Nems.

Injection strategies have been employed in the field of fluidic MEMS using piezo electric or thermal actuators. A very popular application for such technology is inkjet printing. Largely this technology is used to produce droplets of fluid in air; the aim of this investigation is to produce an injection device for the precise dispensing of nanolitre volumes of fluid. A novel technique for dispensing fluid using superparamagnetic beads has been investigated. The beads used (Dynal Biotech) contain a homogeneous dispersion of Fe₂O₃, allowing for easy control with a magnet. This magnetic property is exploited, by a plug of approximately 60 000 beads within a micro channel. This is accomplished by applying a non-uniform magnetic field from a bullet magnet within close proximity of the bead plug. Once the plug is formed it can be moved along the micro channel by moving the magnet and thus, provide a plunger-like action. Previous work has demonstrated a bead plug device is able to dispense fluid from a micro channel at rates up to 7.2μlmin^-1. This is an investigation using silicon and Pyrex fabricated micro channels with smaller dimensions, such that the dimensions will be similar to those which will be used to produce a pipette device. Here results are presented using these fabricated micro channels, where the effects of using differently sized bead plugs and varying velocities are examined. The results follow our proposed theory; further analysis is required to determine the operation of a bead plug during all states of movement.

A device based in microsystem technology for extracting and storing fluid samples is presented in this paper. The solution presented in this paper is a controlled low-cost extractor. The main advantage of this device against other solutions used so far, is the control over the activation of the extraction. Its main features are a very simple structure and easy method of activation. The structure is so useful that can be used to obtain an injector too. Another advantage is its manufacture in plastic, which simplifies its fabrication and decreases the cost. A reactive can be located in it to sense the chemical substances concentration of the absorbed fluid. In this case, two electrodes are included in the design.

Combination of micromachined platforms and chemically sensitive micro-beads have been demonstrated for use as multi-analyte chemical and biological agent detectors [1,2]. In many of these systems agarose beads have been used as the "container" of various chemical sensors and enzymes. This paper discusses a method of array assembly using such sub-millimeter size beads.

Microfluidic analysis devices, often referred to as Micro Total Analysis Systems or the Lab-on-a-chip, are often based on the manipulation of small volumes of fluid. These devices require the design and fabrication of components for fluid handling, control and measurement, such as micropumps, micromixers and flow sensors. The fabrication of miniature versions of large scale components such as pressure sensors and flow rate meters has been demonstrated. However, complicated fabrication is prohibitive and devices which involve flow constriction can be prone to blocking if particle containing samples are used. This paper presents results of the design and fabrication of a microimpedance measurement cell, designed to measure the impedance of sub-nanolitre volumes of fluids. The measurement system was designed to measure the electrical impedance at several different frequencies, allowing identification and analysis of the material contained within the sample volume. Measurements of different fluids at different flow rates through a microchannel containing the measurement cell are presented. The use of this system as a solid state flow rate sensor is then discussed.

For the past two decades intensive research has been carried out on the development of environmental sensors. Nevertheless, the applicability of such devices has been hindered by harsh work conditions and the complexity of the sample matrices. A novel approach centres on the integration of sample pre-treatment steps, where the technology involved can be used advantageously for the design of a Micro Total Analysis System (fluid motion and detection enhancement). The synergistic mixed surfactant system allows the development an independent "green" target specific extraction scheme. Amphiphiles are routinely used in the electrophoretic separation process for their intrinsic detection signal enhancement (i.e. by optical/electrochemical methods). They can also be regarded as a means of flow generation (e.g. Marangoni's Flow) in micro-systems. In this perspective, we are currently developing micro-systems based on glass and polymeric substrates (e.g. poly dimethyl silicone). Whilst the surface chemistry of glass substrates allows the integration of mesoporous silica and ceramics, soft lithographic methods, such as micro-moulding or prototyping, renders the design of PDMS substrate simple. While the selectivity of the system may be based on molecular imprinted silicates, biologically compatible ceramics such as titanium dioxide can be used for the design of a single optical/ electrochemical detection cell. All of these previously cited technologies form a standing bridge towards independent, automated, at-/on-line sensor systems.

This work investigates the fabrication of a linearly tunable capacitor using the standard CMOS (Complementary Metal-Oxide Semiconductor) process and a maskless post-process. This tunable capacitor is composed of a comb-drive actuator, a parallel capacitor and supported beams. The comb-drive actuator is employed to change the position of the movable electrode plate in the parallel capacitor, such that the overlap area between the two plates in the parallel capacitor is changed. The capacitance of the tunable capacitor is a linear variation. The benefits of the pos-process are compatible with the CMOS process and etching without mask. The post-process has two main steps. One is the use of phosphoric acid to remove the metal from sacrificial layers and etch holes. The other step employs RIE (reactive ion etching) to etch the passivation layer over the pads. The experimental results show a capacitance of 500 fF, and 50% tuning range at 20 V.

Conducting polymers, due to their property of oxidize and reduce in a reversible way, have largely been studied as adequate materials for constructing actuators. The volume change produced in these processes is used for the stuck of a conducting polymer film on a not-volume-changing layer for the development of artificial muscles. One of the main drawbacks that these multilayer artificial muscles show lies on the fact that they delaminate after several working cycles. In one of our previous works, a simplified, single film, self-supported artificial muscle was developed assembling different polypyrrole structures in the same synthesis process. This produces not only "all-polymeric" but rather "all-conducting-polymer" artificial muscles that are able to move in electrolytic media without showing delamination problems after long cycling times. This new generation of simplified artificial muscles seems to be suitable for biomedical related applications. In the present work, actuator’s basement is explained and design configurations analyzed.

A new concept of the fabrication process for glass microlenses (external diameter ED<1 mm, focal length a few millimeters), based on the silicon master mask-less anisotropic wet etching in KOH, vacuum anodic bonding and re-flow of borosilicate glass, followed by the precise wafer-scale polishing and DRIE has been presented. A single spherical microlens as well as an array of spherical microlenses with focal length between 44.8 and 8.6 mm and external diameter 0.35 to 0.985 mm have been repeatable manufactured.

The effects of electron beam lithography for patterning to the nanoscale a polysilicon layer electrically connected to the gate of an NMOS transistor are investigated by means of the analysis of the transistor current-voltage characteristics. In order to evaluate the impact of the electron beam process, two sets of experiments are carried out. The first set consists in the assessment of the effect on the transistor when directly exposing the polysilicon layer and in the second, the impact of the complete electron beam lithography process is investigated using different acceleration voltages. The results obtained show that a severe degradation of the transistor characteristics occurs when processing at high acceleration voltages. The degradation is observed as a threshold voltage shift and a decrease in the transconductance. This behaviour can be related to positive charge trapping in the gate oxide and generation of interface states at the SiO₂-Si interface. In addition unbiased room temperature annealing is found to significantly reduce or compensate the induced positive trapped charges. The results suggest that the secondary radiation created by the primary electron beam is damaging the transistor characteristics and can lead to the loss of circuit performance when using electron beam lithography to fabricate nanostructures in already processed CMOS circuits.

This paper presents the design, simulation and performance evaluation of an area-changed capacitive accelerometer for low-g applications. The movable mass of the accelerometer was designed with many fingers connected in parallel and suspended over stationary electrodes composed of differential comb fingers by means of suspension beams anchored onto the substrate. An area-changed differential capacitance method was used to sense the deflection of the proof mass. A folded suspension design with low spring constant and low cross-axis sensitivity was chosen. The simulation was performed using Coventorware2001.3 software. A 3-mask bulk micromachining wafer bonding fabrication process was utilized to produce this accelerometer. Silicon-on-glass was used to achieve high sensitivity and low mechanical noise while maintaining a simple structure. The general concept, main design considerations, fabrication procedure and performance of the resulted accelerometer was elaborated and presented. A linear relationship between the differential capacitance and acceleration was obtained. The accelerometer sensitivity was calculated to be 0.47pF/g with an acceleration range of ±5g.

In this work, we describe the design implementation, validated by experimental results, of an innovative gas sensor array for wine quality monitoring. The main innovation of this integrated array deals with the simultaneous outputs, from a single chip on TO-12 socket, of 8 different signals coming from a WO3 thin film structure heated in a linear temperature gradient mode, allowing an overall evaluation of gas sensing properties of the material in a 100°C-wide window, typically from 300 to 400°C. The implemented sensitive layer is a WO3 film deposed by RF-sputtering. Preliminary tests of gas sensing showed good responses to the target analytes for the specific application (1-heptanol, 3-methyl butanol, benzaldehyde and ethyl-hexanoate).

Metal oxide gas sensors are widely used for different applications and operate normally at high temperatures between 300°C and 600°C. Such high temperatures are mainly needed to speed up the desorption of molecules from the gas sensor surface. Goal of the reported investigations is the reduction of the operating temperatures of such devices by the influence of radiation on the gas adsorption/desorption process. Therefore, the influences of radiation on the gas sensing mechanisms at surfaces of different metal oxides (SnO₂, ZnO, WO₃ and Cr_2-xTi_xO_3+z) have been studied for different wavelengths. The experiments were carried out at an operating temperature of 130°C as well as at room temperature. As radiation sources LEDs emitting at different wavelength were used. The sensor response to NO₂, CO, NH₃ and H₂ has been measured with and without illumination. The investigations have shown that light mainly influences the photo-activation of electron-hole pairs, which results in an increasing of the electrical conductivity of the illuminated metal oxide. The observed influences of photoadsorption and photocatalytic effects are small compared to the photoelectric effect. Only a weak increase of the NO₂ sensitivity during illumination has been measured.

Nanostructured TiO₂ films and Au-TiO₂ nanocomposite thin films prepared by sol-gel method have been deposited onto gold covered glass substrates and glass substrates in order to study their optical properties using Surface Plasmon Resonance and Optical Absorption measurements. Both techniques have been used to study the sensing features of both kind of films to different vapour organic compounds. A comparative study of the two techniques has allowed us to know the possible benefits than can be found when the sensing material is a nanocomposite thin film.

This paper reports the thermoelectric properties of intrinsic N-type bismuth telluride (Bi₂Te₃) thin films (2.5-10 μm thickness). These films were deposited using radio frequency (R.F.) magnetron sputtering. These properties include; Seebeck coefficient and electrical resistivity at different temperatures. It has been observed that the Seebeck coefficient and electrical resistivity of thin films are approximately -150 μV/°C and 4 x 10^-5 ohm-m at room temperature, respectively. The maximum value of Seebeck coefficient of approximately -287 μV/°C was observed at 54 °C for a film thickness of 9.8 μm. The microstructural characteristics of the thin films were investigated using Scanning Electron Microscopy and X-Ray Diffraction analysis. It was observed that the thicker the Bi₂Te₃ film, the larger the grain size. The observed grain sizes were approximately 900 nm and 1500 nm for Bi₂Te₃ film of 2.6 μm and 9.8 μm thicknesses, respectively. The XRD analysis indicated the presence of rhombohedral (Bi₂Te₃) crystal structures.

In order to make EAP actuators technology scalable a design methodology for polymer actuators is required. Design variables, optimization formulas and a general architecture are required as it is usual in electromagnetic or hydraulic actuators design. This will allow the development of large EAP actuators from micro-actuator units, specifically designed for a particular application. It will also help to enhance the EAP material final performance. This approach is not new, since it is found in Nature. Skeletal muscle architecture has a profound influence on muscle force-generating properties and functionality. Based on existing literature on skeletal muscle biomechanics, the Nature design philosophy is inferred. Formulas and curves employed by Nature in the design of muscles are presented. Design units such as fiber, tendon, aponeurosis, and motor units are compared with the equivalent design units to be taken into account in the design of EAP actuators. Finally a complete design methodology for the design of actuators based on multiple EAP fiber/sheets is proposed. In addition, the procedure gives an idea of the required parameters that must be clearly modeled and characterized at EAP material level prior to attempt the design of complex Electromechanical Systems based on Electroactive Polymers.

The growing interest in biological micro-array and Lab-on-Chip (LOC) is justified by the possibility of reducing the sample volume, processing time and costs. By means microfluidics seems to be the prevalent tool for the integration of manifold processes in miniaturized devices. Anyway at a sub-millimeter scale the liquid behavior is affected by geometric confinement and wetting properties. In order to confine the liquid sample inside the LOC buried channels we have performed the sealing by poly(dimethylsiloxane)~(PDMS), a silicon-based bi-component elastomer. The filling dynamics changes at changing of the polymer mixing ratio of the pre-polymer and the curing agent. In fact, a different concentration of cross-linker modifies the elastic, adhesion and wettability properties of the cover-slip

This paper presents a three dimensional micro capacitive tactile sensor that can detect normal and shear forces which is fabricated using deep reactive ion etching (DRIE) bulk silicon micromachining. The tactile sensor consists of a force transmission plate, a symmetric suspension system, and comb electrodes. The sensing character is based on the changes of capacitance between coplanar sense electrodes. High sensitivity is achieved by using the high aspect ratio interdigital electrodes with narrow comb gaps and large overlap areas. The symmetric suspension mechanism of this sensor can easily solve the coupling problem of measurement and increase the stability of the structure. In this paper, the sensor structure is designed, the capacitance variation of the proposed device is theoretically analyzed, and the finite element analysis of mechanical behavior of the structures is performed.