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In this work, we investigate the correlation between tensile residual stress and Q-factor of double-clamped beams fabricated on epitaxial 3C-SiC layers grown on both and silicon substrates, using a completely optical measurement setup to measure the Q-factor of the resonators and the residual stress of the layers by means of purposely designed micromachined test structures. From the measurements, a clear correlation appears between the residual stress of the SiC layer and the Q-factor of the resonators, with Q-factor values above half a million for resonators fabricated on substrates, showing residual stress around 1 GPa.

Extreme weather conditions, climate change, damages to the infrastructure (caused by natural and man-made hazards) and traffic impediments negatively impact the reliability of mobility solutions. Risk analysis, adaptation measures and strategies that enable minimizing the impact of both natural and man-made extreme events on seamless transport operation, protect the users of the transport network in case of extreme conditions, as well as provide optimal information to operators and users of the transport infrastructure, need to be developed. Road transport is vulnerable to extreme weather events, while bridges and tunnels are among the most critical land transport structures. A large number of bridges and tunnels have been in operation for more than 50years and there are widespread signs of deterioration. They need inspection, vulnerability assessment and, when needed, appropriate interventions. Inspection, though, in inaccessible areas, or structures with high volumes of traffic, is expensive, time-consuming, and potentially dangerous. At the same time, structural/vulnerability assessment is also a lengthy process which is especially painful after extreme events. The overall goal of RESIST (RESilient transport InfraSTructure to extreme events) a RIA H2020 project funded by the EU commission with grant number 769,066 is to increase the resilience of seamless transport operation to natural and man-made extreme events, protect the users of the European transport infrastructure and provide optimal information to the operators and users of the transport infrastructure. In the context of RESIST, robotics for visual and contact inspection of structures, structural vulnerability assessment, infrastructure risk management as well as mobility continuity applications considering stress levels of the drivers are being developed towards a high level of resilience of the transport infrastructure.

The application of high-resolution MEMS strain sensors based on micromechanical resonators fabricated with wafer-level vacuum packaging to the construction of large dynamic range weighing systems is explored. Resonant sensors with sub-nano strain resolution are adopted to build a load cell prototype using a standard aluminum structure normally utilized in commercial weighing systems. A differential strain measurement configuration is implemented with two sensors oriented at 90° between them and fabricated on the same chip for temperature compensation. The load cell equipped with the resonant MEMS sensors shows an excellent dynamic range of 108 dB, effective temperature compensation and good weight measurement reproducibility.

A new strain sensor design based on vacuum packaged Double-Ended Tuning Fork silicon resonators with a strain amplification mechanism is presented. The sensors are fabricated with a Silicon On Insulator MEMS process including a thin-film vacuum encapsulation technology that permits to obtain high-Q resonators operating at a vacuum level around 160 mTorr. Within the encapsulation, a strain amplification structure consisting in a long beam connected to the DETF resonator is integrated in order to increase the sensitivity of the device to the applied strain. Thanks to such amplification, an unprecedented sensitivity of $200 \text{Hz}/\mu\varepsilon$ in bending tests on steel is demonstrated, operating the sensors in closed loop with an external readout circuit.

This paper will focus on design, fabrication and characterization of a new MEMS capacitive microphone with the perforated diaphragm supported by Z-shape arms using SOI wafer. The aim is to fabricate a new microphone with the smallest size, simple and low cost. The novelty is making Z-shape arms around of diaphragm on SOI wafer using only a mask to decrease diaphragm stiffness and air damping and thus improve microphone performances. The fabricated structure has a diaphragm thickness of 5 µm, a diaphragm size of 0.3 mm × 0.3 mm, and an air gap of 1 µm. The results show that the pull-in voltage is 10.3 V, open circuit sensitivity of 2.46 mV/Pa, and resonance frequency of 60 kHz. The fabrication process uses minimal number of layers and masks due to using SOI wafer to reduce fabrication time and cost. The specific geometry of the proposed diaphragm causes the new fabricated microphone has low bias voltage, good sensitivity and smallest size compared with previous works.

In this paper, we present a new design of MEMS condenser microphone using SOI wafer. To improve the performance of the microphone, a perforated diaphragm with C-shape slots has been designed. The aim is to achieve high sensitivity, low voltage and small size microphone with easy and low cost fabrication process. The structure has a diaphragm thickness of 5 A mu m, a diaphragm size of 0.38 mm x 0.38 mm. The novelty of this microphone relies on perforated diaphragm includes some C-shape slots to reduce the stiffness of diaphragm to decrease the bias voltage and increase the sensitivity. Moreover, the proposed microphone is fabricated on SOI wafer to minimize the number of masks, deposited layers and fabrication process. The new microphone can be fabricated using just one mask to pattern the proposed diaphragm. The deflection of the new diaphragm is increased 19.5 times rather than traditional clamped diaphragms under an equivalent acoustic pressure of 20 Pa. The results show that the pull-in voltage is 10.47 V, open circuit sensitivity of 3.16 mV/Pa and resonance frequency of 70 kHz. The new microphone has a better figure of merit rather than other MEMS condenser microphones.

3C-SiC is an emerging material for MEMS systems thanks to its outstanding mechanical properties (high Young’s modulus and low density) that allow the device to be operated for a given geometry at higher frequency. The mechanical properties of this material depend strongly on the material quality, the defect density, and the stress. For this reason, the use of SiC in Si-based microelectromechanical system (MEMS) fabrication techniques has been very limited. In this work, the complete characterization of Young’s modulus and residual stress of monocrystalline 3C-SiC layers with different doping types grown on and oriented silicon substrates is reported, using a combination of resonance frequency of double clamped beams and strain gauge. In this way, both the residual stress and the residual strain can be measured independently, and Young’s modulus can be obtained by Hooke’s law. From these measurements, it has been observed that Young’s modulus depends on the thickness of the layer, the orientation, the doping, and the stress. Very good values of Young’s modulus were obtained in this work, even for very thin layers (thinner than 1 μm), and this can give the opportunity to realize very sensitive strain sensors.

This paper presents a robotic platform, capable of autonomous tunnel inspection, developed under ROBO-SPECT European union funded research project. The robotic vehicle consists of a robotized production boom lift, a high precision robotic arm, advanced computer vision systems, a 3D laser scanner and an ultrasonic sensor. The autonomous inspection of tunnels requires advanced capabilities of the robotic vehicle and the computer vision sub-system. The robot localization in underground spaces and on long linear paths is a challenging task, as well as the mm accurate positioning of a robotic tip installed on a five-ton crane vehicle. Moreover, the 2D and 3D vision tasks, which support the inspection process, should tackle with poor and variable lighting conditions, low textured lining surfaces and the need for high accuracy. This contribution describes the final robotic vehicle and the developments as designed for concrete lining tunnel inspection. Results from the validation and benchmarking of the system are also included following the final tests at the operating Egnatia Motorway tunnels in northern Greece.

An ultrasonic probe consisting of two optical fiber-based miniaturized transducers for wideband ultrasound emission and detection is employed for the characterization of in vitro biological tissues. In the probe, ultrasound generation is obtained by thermoelastic emission from patterned carbon films in Micro-Opto-Mechanical-System (MOMS) devices mounted on the tip of an optical fiber, whereas acousto-optical detection is performed in a similar way by a miniaturized polymeric interferometer. The microprobe presents a wide, flat bandwidth that is a very attractive feature for ultrasonic investigation, especially for tissue characterization. Thanks to the very high ultrasonic frequencies obtained, the probe is able to reveal different details of the object under investigation by analyzing the ultrasonic signal within different frequencies ranges, as shown by specific experiments performed on a patterned cornstarch flour sample in vitro. This is confirmed by measurements executed to determine the lateral resolution of the microprobe at different frequencies of about 70 mu m at 120 MHz. Moreover, measurements performed with the wideband probe in pulsed-echo mode on a histological finding of porcine kidney are presented, on which two different spectral signal processing algorithms are applied. After processing, the ultrasonic spectral features show a peculiar spatial distribution on the sample, which is expected to depend on different ultrasonic backscattering properties of the analyzed tissues. (C) 2016 Elsevier B.V. All rights reserved.

A novel Micro-Opto-Mechanical acoustic sensor that can be utilized to measure the width of surface opening cracks in concrete structures from aerial robots is presented. The sensor is used in combination with a piezoelectric emitter operating at 54 kHz in a crack width measurement procedure that provides a resolution around 0.2 mm. The method is tolerant to pressure variations during contact with concrete, which may easily occur when operating the sensors from aerial robots.

Silicon resonators fabricated with wafer-level vacuum packaging on ultrathin silicon chips (overall thickness around 60 ?m) are utilized for strain measurements on steel slabs. The thinned chips are glued on steel using M-bond 610 and Loctite EA 9461 adhesives and the sensor response during bending tests performed while operating the resonators in closed loop is measured, evaluating possible non-ideal effects such as creep and hysteresis. In the measurements, the results obtained on the ultrathin chips are compared with those achieved on sensors manufactured on the native 500 ?m thick silicon substrates. The results obtained show an astonishing improvement in the measurements realized with the thinned chips, which show creep levels below 0.1%, no appreciable hysteresis phenomena and strain measurement range extended beyond 850 ??, indicating that chip thinning can be a viable way to obtain high-quality strain measurements on a large range by vacuum-packaged silicon MEMS resonators.

The paper reports on the fabrication and characterization of flexural resonators designed for resonant strain sensing and manufactured using 2 $\mu \text{m}$ thick monocrystalline 3C-SiC layers grown on Silicon-On-Insulator substrates. The resonators are designed with Double-Ended-Tuning Fork geometry and actuated electrostatically using lateral electrodes fixed on the sides of the resonator tines, through coupling gaps with average width of 1.03 $\mu \text{m}$ . They show excellent performance in vacuum environment with Q-factor around 30,000 and 18 dB high resonance peaks measured in open loop with DC bias voltage of 20 V. The closed-loop operation of the resonators with an external transimpedance amplifier feedback circuit is demonstrated and the stability of the resulting MEMS oscillator is analyzed using a microcontroller-based digital readout to measure its oscillation frequency. The results of the Allan deviation tests on the MEMS oscillator indicate a relative frequency stability better than 10−7 on a measurement time of 280 ms. The results of strain sensitivity experiments in vacuum performed after adhesive attachment of the resonator chip on Al are also reported, indicating a sensitivity of 41.7 Hz/ $\mu \varepsilon $ and a resolution of about 0.82 $\text{n}\varepsilon $ for the same measurement time. [2019-0183]

This paper presents an ultra-low power, silicon-integrated readout for resonant MEMS strain sensors. The analogue readout implements a negative-resistance amplifier based on first-generation current conveyors (CCI) that, thanks to the reduced number of active elements, targets both low-power and low-noise. A prototype of the circuit was implemented in a 0.18-µm technology occupying less than 0.4 mm2 and consuming only 9 µA from the 1.8-V power supply. The prototype was earliest tested by connecting it to a resonant MEMS strain resonator.

Sensors are playing a more important role in the modern hydraulic systems. Increasing needs for closed loop controls, high precision measurement, power control and energy monitoring, diagnosis and safety concerns, ask for both pressure and flow acquisition in both industrial and mobile applications. Traditional pressure sensors need specific bored screw for mounting, and both pipes and components must be modified in order to apply pressure sensors. Traditional pressure sensors are related to mini-mess and to oil flow modification in the sensor area. Sensors position in hydraulic circuits or components must be defined at design phase, in order to design the proper screw in desired circuit positions. Most of times sensors result in a efficiency loss in the circuit. Last but not least, the cost of traditional sensors, the need for proper connections for sensors installation and the work needed for sensor placement in machines production phase, could be avoided if sensors could be integrated in smart components. Modern Silicon based technologies offer new solutions for a less invasive pressure measurement. Micro Electro-Mechanical Systems (MEMS) Technology is suitable to design new sensors for indirect pressure measurement. Also traditional technologies, coupled with modern electronics could offer solutions that were not enough precise 10 years ago, but presenting some tricks to be solved accurately. The paper presents the first experimental results of the early stage of application of a MEMS strain gauge sensor application on components, where hydraulic pressure is measured through the component strain due to internal pressure force and component deformation. New sensors called Double Ended Tuning Fork (DETF) MEMS Resonant Extensometer sensor, based on a silicon diapason made in void environment in a system on chip will be applied at components due to the sensor’s sensitivity and precision that can reach the 0,15 nε/ε. At the same time the paper will show that pipes offer a deformation function of the mechanical characteristics and that the pressure effect is causing a deformation that can be even too high for the MEMS sensor. The strain position sensor and component deformation are also proved by the FEM analysis in order to validate both pressure measurement and FEM analysis in respect to test bench results applied to the sensor strain acquisition.

The fabrication and laboratory testing of Micro-Opto-Mechanical sensors for the measurements of width of surface opening cracks in concrete structures are presented. The sensors are designed to be operated on a fan-out connector containing 12 multimode optical fibers, using a microstructure that can be mounted on the connector with a self aligned procedure. Thanks to the optical alignment automatically provided by such mounting method, each fiber in the connector can be used to interrogate an individual pressure sensor within an array composed by 12 elements in total. Using a soft polymer layer between the microsensor and the crack opening, the width of the crack can be derived by means of a tactile measurement performed by interrogating the 12 elements of the array alternatively, with a space resolution of 0.25 mm. The device is designed to be operated on board of a Remotely Piloted Aerial Vehicle equipped with a vision system that will be able to locate surface cracks of the external surface of reinforced concrete bridges and perform contact measurements on cracks using a robotic arm operated from the vehicle.

We have investigated 3C-SiC layers grown on silicon and on poli-Si in order to realize test MEMS structures. The strain of the films were investigated by the fabrication of cantilevers, beams, springs and we successfully fabricated a Double-Ended-Tuning-Fork double clamped SiC resonator on the film, with perfectly aligned actuation electrode.

In this paper the electrical and structural characteristics of n-MOSFETs fabricated on 4H SiC with a process based on nitrogen (N) implantation in the channel region before the growth of the gate oxide are reported for low (5x1018 cm-3) and high (6x1019 cm-3) N concentration at the SiO2/SiC interface. The electron mobility and the free carrier concentration in the MOSFET channel were evaluated by Hall effect measurement. The MOSFETs with the higher N concentration had the best electrical characteristics in terms of threshold voltage and field effect mobility, in spite of a lowering of the electron mobility in the channel. The latter is a negative drawback of the fabrication process that probably can be ascribed to an incomplete recovery of the implantation damage or to a high density of interstitial N atoms present in the channel region. In fact, the MOSFETs with the superior electrical performances were fabricated with the higher N+ dose and the shorter thermal oxidation time. However, no evidence of extended defects, clusters or nano-particles in SiC at the interface with the gate oxide was found in every SiC MOSFETs devices observed by electron transmission microscopy

This paper presents design, modeling, and fabrication of a crab-shape microphone using silicon-on-isolator (SOI) wafer. SOI wafer is used to prevent the additional deposition of sacrificial and diaphragm layers. The holes have been made on diaphragm to prevent back plate etching. Dry etching is used for removing the sacrificial layer, because wet etching causes adhesion between the diaphragm and the back plate. Crab legs around the perforated diaphragm allow for improving the microphone performance and reducing the mechanical stiffness and air damping of the microphone. In this structure, the supply voltage is decreased due to the uniform deflection of the diaphragm due to the designed low-K (spring constant) structure. An analytical model of the structure for description of microphone behavior is presented. The proposed method for estimating the basic parameters of the microphone is based on the calculation of the spring constant using the energy method. The microphone is fabricated using only one mask to pattern the crab-shape diaphragm, resulting in a low-cost and easy fabrication process. The diaphragm size is 0.3 mm x 0.3 mm, which is smaller than the conventional micro-electromechanical systems capacitive microphone. The results show that the analytical equations have a good agreement with measurement results. The device has the pull-in voltage of 14.3 V, a resonant frequency of 90 kHz, an open-circuit sensitivity of 1.33 mV/Pa under bias voltage of 5 V. Comparing with previous works, this microphone has several advantages: SOI wafer decreases the fabrication process steps, the microphone is smaller than the previous works, and crab-shape diaphragm improves the microphone performances. (C) 2018 Society of Photo-Optical Instrumentation Engineers (SPIE)

The paper presents a technology for strain sensing on steel using resonant MEMS packaged in vacuum. For this purpose, a custom sensor fabrication technology and a novel vacuum packaging technique have been developed. The MEMS sensors have been fabricated by surface micromachining of thick (15 μm) Silicon On Insulator substrates with heavily doped handle layers ( ρ = 0.005 Ω cm ) . Using this process, Double-Ended Tuning Fork (DETF) parallel-plate resonators with reduced coupling gaps (less than 1 μm) have been fabricated, using a high-performance Deep Reactive Ion Etching performed on submicrometer features realized by near-UV lithography combined with a maskless line narrowing technique. The devices have been bonded to a thin steel bar by epoxy glue, packaged in vacuum and tested by applying strain to the bar, showing good tolerances to packaging parasitics, measurement reversibility, and strain sensitivity of 10 Hz / μ e .

Micro and nanotechnologies are called to play a key role in the fabrication of small and low cost sensors with excellent performance enabling new continuous monitoring scenarios and distributed intelligence paradigms (Internet of Things, Trillion Sensors). Harvesting devices providing energy autonomy to those large numbers of microsensors will be essential. In those scenarios where waste heat sources are present, thermoelectricity will be the obvious choice. However, miniaturization of state of the art thermoelectric modules is not easy with the current technologies used for their fabrication. Micro and nanotechnologies offer an interesting alternative considering that silicon in nanowire form is a material with a promising thermoelectric figure of merit. This paper presents two approaches for the integration of large numbers of silicon nanowires in a cost-effective and practical way using only micromachining and thin-film processes compatible with silicon technologies. Both approaches lead to automated physical and electrical integration of medium-high density stacked arrays of crystalline or polycrystalline silicon nanowires with arbitrary length (tens to hundreds microns) and diameters below 100 nm.

A new Micro-Opto-Mechanical System (MOMS) probe on optical fiber is presented. High miniaturization levels are reached in the MOMS devices (fiber-optic emitters and detectors with minimum diameter around 350 and 250 µm respectively). The transmitting element consists of an optical fiber with a graphite-compound absorbent layer on the tip. The receiving element is an extrinsic fiber hydrophone based on a Fabry-Perot interferometer, the thickness of which is modulated by ultrasonic signals. The possibility to use optoacoustic sources in conjunction with the fiber-optic acousto-optical detectors within a minimally invasive probe is demonstrated by successfully measuring the ultrasonic echo reflected from a fingerprint made of cornstarch flour and from a silicon substrate with micrometric machining. The ultra-wide bandwidth and the high frequencies allowed by photoacoustic generation, in conjunction with the extreme miniaturization derived from the MOMS technology, can generate images at very high resolution and permits to obtain different “ultrasonic views” of the investigated object.

A new Micro-Opto-Mechanical System (MOMS) technology for the fabrication of optoacoustic probes on optical fiber is presented. The technology is based on the thermoelastic emission of ultrasonic waves from patterned carbon films for generation and on extrinsic polymer Fabry-Perot acousto-optical transducers for detection, both fabricated on miniaturized single-crystal silicon frames used to mount the ultrasonic transducers on the tip of an optical fiber. Thanks to the fabrication process adopted, high miniaturization levels are reached in the MOMS devices, demonstrating fiber-optic emitters and detectors with minimum diameter around 350 and 250 mu m respectively. A thorough functional testing of the ultrasound emitters mounted on 200 and 600 mu m diameter optical fibers is presented, in which the fiber-optic emitter with a diameter of 200 mu m shows generated acoustic pressures with peak-to-peak value up to 2.8 MPa with rather flat emission spectra extended beyond 150 MHz. The possibility to use the presented optoacoustic sources in conjunction with the fiber-optic acousto-optical detectors within a minimally invasive probe is also demonstrated by successfully measuring the ultrasonic echo reflected from a rigid surface immersed in water with various concentration of scatterers. The resulting spectra highlight the possibility to discriminate the effects due to frequency selective attenuation in a very wide range of frequencies within a biological medium using the presented fiber-optic probes.

The design, fabrication, early testing and material property assessment work related to the development of an opto-mechanical pressure sensor implemented with hetero-epitaxial 3C-SiC on silicon is described. The sensor is constituted by a single-crystal 3C-SiC membrane whose deflection upon pressure application is measured using a fiber-optic interferometric readout. The fabrication of sensor prototypes and micromachined 3C-SiC membranes for test purposes is described and the results of bulge tests on the membranes are reported. Functional characterization of the sensor prototypes in the pressure range 0-3 bar is also presented, showing good linearity and reproducibility of the sensor response, sensitivity of roughly 2 mV/bar and estimated pressure resolution around 0.5 bar on a 0-200 bar dynamic range.

Dimensional confinement in silicon nanowires (NWs) is well-known for enhancing phonon scattering, thus leading to a pronounced reduction of thermal conductivity κ with respect to bulk material. The effect of confinement on phonon scattering in nanolayers (NLs), however, has not been fully understood. In this work, thermal conductivity on polycrystalline silicon NLs with roughened surfaces and thicknesses ranging from 30 to 100 nm has been experimentally investigated. For measurement purposes, the nanostructures were fabricated with a dedicated surface nano-machining process, thus producing vertical silicon nanostructures suspended on Al/Si electrodes on a silicon substrate, using SiO2 as a sacrificial layer. By designing such structures in a four-terminal configuration, their κ could be determined by the current-voltage method. Boron doped silicon NLs were examined, at resistivity ranging between 2 and 10 m $$\Upomega$$ cm. We found an increase of phonon scattering from the confinement, since κ decreased steadily with the thickness from values typical of thick films (around 30 W m−1 K−1) down to

The paper reports on the fabrication and characterization of absolute capacitive pressure sensors fabricated by polysilicon low-pressure chemical vapour deposition vacuum packaging on silicon-on-insulator substrates. The fabrication process proposed is carried out at wafer level and allows obtaining a large number of miniaturized sensors per substrate on 1 x 2 mm(2) chips with high yield. The sensors present average pressure sensitivity of 8.3 pF/bar and average pressure resolution limit of 0.24 mbar within the measurement range 200-1200 mbar. The temperature drift of the sensor prototypes was also measured in the temperature range 25-45 degrees C, yielding an average temperature sensitivity of 67 fF K-1 at ambient pressure.

An ultrasonic probe was developed by using, in conjunction, opto-acoustic and acousto-optic devices based on fiber optic technology. The intrinsic high frequency and wide bandwidth associated both to the opto-acoustic source and to the acousto-optic receiving element could open a way towards a “virtual biopsy” of biological tissue. A Micro-Opto-Mechanical-System (MOMS) approach is proposed to realize the broadband ultrasonic probe on micromachined silicon frames suited to be mounted on the tip of optical fibers.

We present a design study aimed at fabricating micromachined thermal emitters for infrared gas sensing with high emission efficiency in the 9-12 μm wavelength range. In order to achieve high optical radiance with relatively low power consumption and possibility of fast thermal modulation, a technology based on dielectric membranes composed by stacked silicon oxide and nitride with platinum heaters is adopted, that guarantees good thermal isolation and reduced thermal mass. The dielectric stack adopted is composed in such a way that its emissivity is enhanced in the wavelength range of concern and an optimized design of the emitter geometry is proposed based on finite element thermal simulations. Some preliminary experimental results are presented about the optical properties of the structural layer and its medium-term reliability when operated with Pt heaters at a temperature around 600°C.

The processing parameters which favour the onset of an impurity band conduction around room temperature with a contemporaneous elevated p-type conductivity in Al+ implanted 4H-SiC are highlighted by comparing original and literature results. In the examined cases, Al is implanted at 300-400 degrees C, in concentrations from below to above the Al solubility limit in 4H-SiC (2 x 10(20) cm(-3)) and post implantation annealing temperature is >= 1950 degrees C. Transport measurements feature the onset of an impurity band conduction, appearing at increasing temperature for increasing Al implant dose, until this transport mechanism is enabled around room temperature. This condition appears suitable to guarantee a thermal stability of the electrical properties. In this study, the heaviest doped and less resistive samples (Al implanted concentration of 5 x 10(20) cm(-3) and resistivity of about 2 x 10(-2) Omega cm) show a carrier density above the Al solubility limit, which is consistent with at least a 50% electrical activation for a 15% compensation. The model of Miller and Abrahams well describes the resistivity data of the lower doped sample, whereas a deviation from the behaviour predicted by such a model is observed in the higher doped specimens, consistent with the occurrence of a variable range hopping at low temperature. (C) 2015 AIP Publishing LLC.

The paper reports on the fabrication and characterization of high-resolution strain sensors for structural materials based on Silicon On Insulator flexural resonators manufactured by polysilicon Low-Pressure Chemical Vapour Deposition vacuum packaging. The sensors present sensitivity of 164 Hz/mu epsilon and strain resolution limit of 150 p epsilon on steel for a measurement time of 315 ms, in both tensile and compressive strain regimes. The readout of the sensor is implemented with a transimpedance oscillator circuit implemented on Printed Circuit Board, in which a microcontroller-based reciprocal frequency counter is integrated. The performance of the sensors on steel are investigated for measurement bandwidths from 1.5 to 500 Hz and a comparison with conventional metal strain gauges is proposed. (C) 2016 Elsevier B.V. All rights reserved.