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In this paper, we introduce a charge integrator as a read-out system for piezoelectric cantilever sensors. The charge integrator is used to monitor the surface charge induced by piezoelectric materials as a function of mechanical stress. This technique improves the response of piezoelectric cantilever sensors in low frequency measurements which makes them suitable for chemical and biological detection. Furthermore, it is capable of real-time, portable and all electrical detection. The detection of alkanethiols on the Au-coated piezoelectric cantilevers is demonstrated to verify the concept.

Thin films of tantalum oxynitride were prepared by reactive magnetron sputtering using a Ta target and N2 and O2 as reactive gases. The nitrogen flow was kept constant while the oxygen flow was pulsed periodically. The film composition evolves progressively from TaO0.25N1.51 to TaO2.42N0.25 while increasing the oxygen pulse duty cycle without any abrupt change in the elemental content. The optical transmission spectra of the films deposited on glass show a “blue shift” of the absorption edge with increasing oxygen content. X-ray diffraction (XRD) patterns of all films exhibit broad peaks typical for nanocrystalline materials. Cross-section film morphology is rather featureless and surface topography is smooth exhibiting very small grains, in agreement with the results obtained by XRD. The optical properties of the films are very sensitive to their chemical composition. All films exhibit semiconducting behaviour with an optical band gap changing from 1.85 to 4.0 eV with increasing oxygen content. In order to evaluate the potential of the tantalum oxynitride films for microelectronic applications some Ta–O–N films were integrated in a MOS structure. The results of the capacitance–voltage measurements of the system Al//Ta–O–N//p-Si are discussed with respect to the chemical composition of the Ta–O–N films.

In today's highly integrated microelectronic systems there is a need for high resolution spatial temperature measurement on chips. The resolution requirements are higher than the infrared imaging system are capable of and the investigated areas of the chips are often being rather large for the most common Scanning Thermal Microscope (SThM). In this article we present two quantitative methods to acquire the thermal map with high resolution on large area. There are two approaches used, noncontact method based on infrared radiation and Scanning Thermal Microscopy (SThM). In both methods the expected thermal properties of the sample were thoroughly calculated and the prediction was in agreement with the experimental results. For the study of infrared radiation the composition of the sample together with the spectral sensitivity of the sensor were taken into account. In the SThM part, there were discrepancies based on unequal conditions during calibration and subsequent measurement. Using the finite element method (FEM) simulation of thermal field the problem has been solved and successfully experimentally verified. For both methods a special sample with embedded thermometer capable of being heated internally or externally was used.

We report on the fabrication and characterization of high-temperature Pt-TSVs. A LPCVD silicon nitride passivation layer was implemented to protect the TSVs from oxidation during high-temperature treatments and wet HF-based post-processing steps, the later being widely used for the release of MEMS mechanical structures. An ohmic contact between the TSV metallization and a silicon device layer was created and maintained, during and after high-temperature treatments. These “via first” TSVs were able to withstand post-processing temperatures up to 850 °C; the specific contact resistance was investigated. Moreover, they are of interest for high temp- perature applications; they operated stably for at least 24 h at up to 450°C.

We report on the realization of a low-cost polymeric optical waveguide made on a plastic foil and used for colorimetric gas detection. Low-temperature processes have been used for the realization of polymeric micro-mirrors and the depositions of the chemochromic reagent on PET foil. The planar waveguide configuration aims at improving the transducer sensitivity and simplifies its fabrication. Indeed, the device is currently produced by standard microfabrication techniques but its configuration and the materials involved make the sensor compatible with large scale and low-cost fabrication techniques. The operation of the optical transducer was applied to a colorimetric gas sensor and validated for the detection of ammonia.

Interdigitated capacitive transducers have been inkjet printed onto flexible substrates and optimized for gas sensing applications. Their characteristics have been improved by tuning the annealing/sintering conditions and making use of additional passivation procedures, such as Ag electroplating with Ni or Parylene-C coating of the whole device surface. The as-prepared transducers printed with Ag ink could be utilized in capacitive gas sensing structures up to 70% relative humidity only. Higher humidity levels irreversibly altered the nominal capacitance and conductance of the devices, limiting their practical application. This drawback could be eliminated through the upgrading routes specified above and stable operation over wide temperature ranges has been achieved. From the acquired data a quite accurate description of the sorption processes, involving the printed conducting layers and the supporting material, has been inferred. Furthermore the parasitic sensitivity to test vapours from the class of Volatile Organic Compounds in the concentration range of Threshold Limit Value - Time-Weighted Average as possible interfering analytes has been estimated. Test gas sensors obtained from the optimized transducers by additional coating with gas sensing films poly(ether urethane) successfully passed the laboratory evaluations and seem to be appropriate for use in real devices. (C) 2012 Elsevier B. V. All rights reserved.

Bridges buckled by film stress call generate a vertical displacement resulting in three-dimensional structures. We have demonstrated a micromirror lifted by buckled bridges and a vertical comb drive actuator. The structures show rounded profiles in a stable manner. The detailed profiles of the bridges and the lifted micromirrors are examined. The relations between the lateral design and its effect on the vertical profile and the dynamic characteristics are studied.

The monitoring of heat flux is becoming more and more critical for many technologies approaching nanometric dimensions. Scanning Thermal Microscopy (SThM) is one of the tools available for thermal measurement at the nanoscale. This measurement technics needs calibration samples. Therefore, micro-hotplates made of platinum heater suspended on thin silicon nitride (SiN) membranes were fabricated for the calibration of Scanning Thermal Microscopy probes. The objective is to obtain heated reference samples with localised resistive temperature sensors (RTD) on the membrane to probe the temperature on a micro-scale area (typically 10×10 μm2). This sensing area is dedicated to (1) quantify the thermal resistance between the SThM tip and hot surface contact; and to (2) evaluate the perturbation induced by the probe on the heat dissipation when the contact measurement is performed. In this communication, we report on the thermal design of low-power calibration chip and their fabrication, as well as the electro-thermal characterization of sensitive RTDs made using e-beam technology. Thermal contact measurements using a thermocouple based SThM probe validated the functionality of the calibration chip. © 2015 The Authors. Published by Elsevier Ltd.

We present a complete wafer level microfabrication process for the production of unimorph MEMS energy harvesters based on thinned bulk piezoelectric ceramic, lead zirconate titanate (PZT), sheets. This process eliminates the need for individual bonding of PZT pieces and proof masses at the chip level while still benefitting from the excellent properties of bulk PZT. With the process presented in this paper, 20 piezoelectric energy harvesters have been fabricated in parallel at the wafer level by bonding a single bulk (PZT) sheet onto a silicon-on-insulator (SOI) wafer using a low-temperature process and structuring the bonded stack with standard microfabrication techniques including thinning of the bulk PZT sheet using mechanical grinding as well as electrodeposition to deposit a thick nickel proof mass on the tip of each cantilever. A single fabricated harvester with an effective volume of 47.82 mm(3) is capable of generating a normalized power density of 3346 mu W cm(-3) g(-2) with an average power of 1.6 mu W under an excitation of 0.1 g (1 g = 9.81 m s(-2)) at a resonant frequency of 100 Hz through an optimal resistive load of 11.8 k Omega Thinned bulk PZT exhibits high power and a useable voltage while maintaining a low optimal resistive load, demonstrating the potential of high performance piezoelectric MEMS energy harvesters using bulk PZT sheets fabricated at the wafer level. (C) 2014 Elsevier B.V. All rights reserved.

We present a microfabricated alkali vapor cell equipped with an anti-relaxation wall coating. The anti-relaxation coating used is octadecyltrichlorosilane and the cell was sealed by thin-film indium-bonding at a low temperature of 140 degrees C. The cell body is made of silicon and Pyrex and features a double-chamber design. Depolarizing properties due to liquid Rb droplets are avoided by confining the Rb droplets to one chamber only. Optical and microwave spectroscopy performed on this wall-coated cell are used to evaluate the cell's relaxation properties and a potential gas contamination. Double-resonance signals obtained from the cell show an intrinsic linewidth that is significantly lower than the linewidth that would be expected in case the cell had no wall coating but only contained a buffer-gas contamination on the level measured by optical spectroscopy. Combined with further experimental evidence this proves the presence of a working anti-relaxation wall coating in the cell. Such cells are of interest for applications in miniature atomic clocks, magnetometers, and other quantum sensors. (C) 2014 AIP Publishing LLC.

This paper presents the design and development of a coplanar capacitive proximity sensor for the detection of the gap between the edges of dielectric foils. The finite element analysis is applied to study the design of the sensor by investigating the effects of different physical parameters, like, the sensing electrodes width, the spacing between them and the thickness of the substrate on its responses. The sensitivity of the sensor increases with the ascending electrode width; but is negatively affected by the growing spacing between electrodes. Conversely, the foil edge gap detection range rises with the growing electrode width and spacing between electrodes. Moreover, the optimum sensor performance is observed for the foil edge gap positioned centered with the sensing electrodes and the target foil remaining in contact with its surface. The capacitive proximity sensor with optimum set of parameters is fabricated on a polyimide foil by the inkjet of the sensing electrodes. The sensor demonstrates an average optimum sensitivity of 0.105 fF/μm for an edge gap detection range of 500 µm with a 450 µm thick polyethylene foil, when the vertical gap between the foil and the active area of the sensor is maintained to zero. The sensitivity and the detection range capability reduce significantly with the increasing vertical gap between the sensor and foil.

Stretchable conductive fabric-based triboelectric generator (TENG), to develop breathing/chest band for harvesting energy at low frequency has been developed. Stretchable conductive nylon-fabric and carbon-based elastomer composites were used as electrodes. During this work, film casting technique was implemented and combination of different materials, such as, polydimethylsiloxane (PDMS) and polytetrafluoroethylene (PTFE)/ polyurethane (PU) were tested as triboelectric layers. The process was compatible with large scale fabrication. At low operation frequency of 1.0±0.1 Hz for the strain of 13±1.5%, developed TENGs provide output power densities of 0.06 μW/cm2 and 0.11 μW/cm2 for the load resistance of 100 MΩ, and energy density of 0.19±0.03 nJ/cm2/cycle and 0.08±0.01 nJ/cm2/cycle for the use of capacitor of 2.2 μF, for PDMS-PTFE and PDMS-PU based TENGs respectively.

Temperature, gas and humidity resistive/ capacitive sensors on flexible substrates from organic materials, suitable for RFID mobile applications, have been produced and investigated. The sensor implementation solutions are providing simple, versatile and low power temperature and gas detection. The device structure was developed together with the data evaluation strategies based on last generation SigmaDelta analog (resistance and capacitance) to digital converters. We demonstrate the possibility of developing gas sensors on humidity sensitive substrates, having temperature corrected responses. The proposed device concept is aimed to evolve towards "flexible & full plastic" implementations.

A high‐voltage flip‐flop combining two self‐powered soft sensors with a flexible high‐voltage thin film transistor (HVTFT) is reported, and is used to electrically latch dielectric elastomer actuators (DEAs) in zero and high‐strain states. Two touch‐actuated triboelectric generators (TENGs) provide the gate input for the HVTFT that drives a DEA. One TENG is of positive polarity, while the other is of negative polarity, thus generating voltages either higher (100 V) or lower (−6 V) than the HVTFT threshold voltage. Used in a high‐voltage inverter configuration, there are two stable output voltage states, here 650 V (the “reset” state) and 50 V (the “set” state). The DEA is thus latched in one of two states, at 17.5% and 0% strain. The 650 V output is stable in time, while the 50 V state drifts up to 350 V after 10 s. Due to the highly nonlinear strain–voltage curve of the DEA, the drift of the output voltage in the “set” state leads only to a 2% increase of the DEA actuation strain in 10 s. By enabling bistable control of DEAs with TENGs, the TENG‐HVTFT latch paves the way toward soft robots with flexible embedded control circuitry.

The rapid evolution of the neuromorphic computing stimulates the search for novel brain-inspired electronic devices. Synaptic transistors are three-terminal devices that can mimic the chemical synapses while consuming low power, whereby an insulating dielectric layer physically separates output and input signals from each other. Appropriate choice of the dielectric is crucial in achieving a wide range of operation frequencies in these devices. Here we report synaptic transistors with printed aluminum oxide dielectrics, improving the operation frequency of solution-processed synaptic transistors by almost two orders of magnitude to 50 kHz. Fabricated devices, yielding synaptic response for all audio frequencies (20 Hz to 20 kHz), are employed in an acoustic response system to show the potential for future research in neuro-acoustic signal processing with printed oxide electronics.

This paper presents the development of a compact energy harvesting configuration to convert low frequency, mechanical oscillations into usable electrical energy using AFM-like MEMS piezoelectric cantilevers coupled to a rotating gear. In this approach, one or several piezoelectric harvesters can be positioned above a rotating gear driven by an oscillating mass. In order to analyze the motion and the electrical power output from the harvester, analytical and finite element models have been developed. The harvester, with an active device volume of 3.5 mm(3) (3x5x0.23 mm(3)), is able to produce an average output power of 12 mu W measured across an optimal resistive load of 4.7 k Omega at a rotational speed of 19 rps, demonstrating the potential of the compact MEMS piezoelectric micro-power generator.

In this paper, we have reported the use of buckled bridges for realizing the vertical comb drive actuators. The detailed characteristics of the buckled bridges and the lifted micromirror using film stress are also examined

The monitoring of heat flux is becoming more and more critical for many materials and structures approaching nanometric dimensions. Scanning Thermal Microscopy (SThM) is one of the tools available for thermal measurement at the nanoscale and requires calibration. Here we report on a micro-hotplate device made of a platinum heater suspended on thin silicon nitride (SiN) membranes integrating specific features for SThM calibration. These heated reference samples can include a localized resistive temperature sensors (RTD) or standalone platinum membranes (typically 10 × 10 μm2) on which the temperature can be measured precisely. This functional area is dedicated to (1) estimate the thermal resistance between the SThM tip and hot surface contact; and to (2) evaluate the perturbation induced by the probe on the heat dissipation when the contact measurement is performed. The thermal design of these low-power calibration chips, their fabrication, including sensitive RTDs patterned using e-beam technology, as well as their electro-thermal and electro-mechanical characterizations are presented. Robust operation of the chips up to 500 °C has been demonstrated with their membrane mechanically stable up to 250 °C and a low-power consumption of 16 mW at this operating temperature. The temperature mapping of the active areas was performed using two physical principles: local SThM temperature measurement using a thermocouple-based micro-probe and optical imaging using Near-Infrared (NIR) microscopy. Measurements coupling on one hand SThM probe and the integrated RTD and, on the other hand, SThM probe with optical imaging, validated the functionality of the calibration chips. The latter open new perspectives in the calibration of SThM probes.

The design of low-cost and low-power optical transducers on plastic foil for colorimetric gas sensors is proposed. The transducer was fabricated from PET or PEN foil on which polymeric micro-mirrors and colorimetric film were patterned using additive techniques. It consisted of a planar optical waveguide that was covered with an inkjet printed ammonia sensitive film for its evaluation. A parametric study was performed on the waveguide configuration to reduce the light loss and improve the gas sensing characteristics. The use of polymeric substrate made the device more cost effective and compatible with large scale fabrication, such as roll-to-roll processes. Combined with a low-power interface circuitry operating in pulsed mode, the limit of detection was defined as a function of the power consumption. Sub-ppm concentrations of NH3 were measured at a consumption of 868 mu W. Such potentially low-cost and low-power sensors foresee applications in the field of wireless systems, for environmental and safety monitoring. (C) 201 1 Elsevier B.V. All rights reserved.

Aerosol assisted CVD (AACVD) is a self-catalyzed method that allows for growing single crystalline metal oxide nanowires at moderate temperatures (i.e. up to 380C). This is employed here to grow either Pt or Au-decorated tungsten oxide nanowires directly on flexible polymeric hotplates. E-SEM, EDX and XRD analysis have been used to investigate the morphology and the composition of the nanostructures grown. The functionality of the devices has been demonstrated by testing their gas sensing properties to ethanol, hydrogen and nitrogen dioxide. These flexible sensors show excellent and fast responses, good baseline recovery and repeatability. Tested over a few months, they show also excellent stability. These sensors are good candidates for being integrated in flexible tags for air quality control. © 2014 The Authors. Published by Elsevier Ltd.

International audience; We report on novel MEMS micro-transducers made of diamond and used for bio-sensing applications. To overcome the non straightforward micro-machining of diamond, we developed an original process involving the patterned growth of diamond using the CVD (chemical vapour deposition) technique, inside micro-machined silicon moulds.Typical MEMS structures were successfully fabricated and include cantilevers and bridges. They were actuated using Laplace forces. The structures were characterized by measuring their first mode resonance (frequency and Q-factor) using laser interferometry. The measured data fitted the simulated data and comparison with equivalent silicon structures showed the superior resonant properties of diamond cantilevers. It implies that the later are potentially more sensitive transducers than their silicon counterpart.

244 pages; In the field of gas detection, one major trend is to miniaturize analytical techniques. In such technological developments, the gas pre-conditioning is usually very important. This may involve, firstly, the modification of a gas mixture, for example to improve the selectivity of a detection device, secondly, the effect of preconcentration in order to increase the sensibility of the detector. Indeed, in some applicative environments the concentration of gas is too small and therefore a preconcentration unit at the entrance of the analytical device is needed. When a preconcenrator is used, the gas mixture to be analyzed flows through it and is accumulated during some time, then the mixture is desorbed by a temperature pulse and brought to the detector. This work presents the development of a gas preconcentrator based on a micro-channel in porous and non-porous silicon filled with an adequate adsorbent material by micro-fluidic process in open micro-device or by impregnation in close one. The particularity of this device is its applicability in the fields of atmospheric pollution monitoring (Volatiles Organic Compounds-VOCs) and explosives detection (nitroaromatic compounds). Various designs of micro-devices have been investigated and a special focus has been dedicated to the carbon adsorbent. The optimization of the device and its operation were driven by its future application in outdoor environments. The benefits of using porous silicon to ease the fixing of the carbon absorbent in the reactor and to modify the gas desorption kinetic are also investigated.; Dans certains cas, la concentration du gaz à détecter est si faible qu'elle est en dessous de la limite de détection des capteurs usuels et donc la présence d'une unité de préconcentration en amont du capteur devient indispensable. Le principe de cette technique repose l'accumulation du gaz à détecter au moyen d'un adsorbant qui , ensuite sous l'effet d'une hausse brusque de la température, est désorbé puis redirigé vers un détecteur, entraînant ainsi une amplification de la concentration du gaz vu par ce détecteur. Cette thèse présente le développement d'un préconcentrateur pour la détection de substances chimiques à l'état de trace gaz. Ce micro-préconcentrateur sera constitué d'un microcomposant en silicium rempli d'un adsorbant et muni d'une résistance chauffante à son dos et de capillaires métalliques servant de connectiques fluidique à l'entrée et à la sortie du dispositif. La particularité de ce dispositif repose sur son applicabilité aussi bien dans le domaine de la surveillance de la pollution atmosphérique (Benzène, Toluène, Xylène...) que la détection d'explosifs (composés nitroaromatiques). Différents modèles de micro-dispositifs ont été étudiés et une attention particulière a été consacrée au carbone adsorbant. L'optimisation et le fonctionnement de ce système de préconcentration ont été étudiés suivant son application future. En plus, les avantages de l'utilisation de silicium poreux pour faciliter la fixation de l'adsorbant dans le réacteur et modifier la cinétique de désorption de gaz ont été également étudiés.