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This paper presents the analytical modeling, calculation, experimental validation and feedback compensation of a capacitive MEMS accelerometer based on geometric anti-spring structure (GAS). According to the analytical thermal drift model, asymmetrical structure and the thermal variations in the operating environment result in accelerometer nonlinearity, temperature drift of scale factor (TDSF) and displacement bias (TDB), and were solved with a force-balanced capacitive readout, electronic active compensation and calibration system, respectively. The experimental characterization of the readout circuit indicates a high sensitivity, of $5.721~V/g$ , with a closed-loop nonlinearity of $30~ppm$ for $\pm 1g$ operating range. The proposed analytical thermal drift model,confirmed by finite element analyses (COMSOL Multiphysics), predicts the thermal drifts of the bias and sensitivity. Without active compensation and calibration, the thermal drifts of the resonance frequency, bias and scale factor, for a temperature range from $- 10\,\,{^{\circ }C}$ to $90~{^{\circ }C}$ , are measured to be, respectively, of $3361~ppm$ , $900~mg$ , and $2755~ppm$ ; after the calibration and the active compensation feedback, these values are reduced to $121~ppm$ , $109~\mu g$ , $52.1~ppm$ , respectively. The Allan deviation was measured, in order to verify the effectiveness of the compensation methods, showing an initial uncompensated drift of $151~\mu g$ in the temperature range from $- 10\,\,{^{\circ }C}$ to $90~{^{\circ }C}$ , which is reduced to $41.7~\mu g$ with DC-bias compensation. Therefore, the proposed force-balanced circuit, active compensation and calibration scheme, considerably reduces the temperature-induced drift of the capacitive MEMS accelerometer based on asymmetrical GAS. [2020-0070]

Recent advances in ultrasonic transducer technologies have made it possible to build flexible ultrasound arrays that can conform to body parts. However, in order to perform beamforming and image reconstruction, it is necessary to estimate the transducer shape. While external shape measurement devices could be used, we propose here an algorithm that uses intrinsic characteristics of reconstructed ultrasound images to iteratively estimate the array shape. The algorithm maximizes an image focus metric based on gradient energy in the region of interest. We simulated three realistic shoulder sonograms created by a relatively large 98-mm, 384-element ultrasound array with varying profile shapes representing anatomically realistic curved array shapes (radii of curvature: 62–125 mm). The average relative position estimation error was less than 1% across the nine studied cases, and the median Complex Wavelet Structural Similarity index between reference and reconstructed images was 98% (range: 84%-99%). The proposed method could facilitate implementing flexible ultrasound probes in clinical settings.

Flexible components have always been an attraction in all engineering fields; ultrasound transducers are no exception to this. Capacitive micromachined ultrasound transducers (CMUTs) have started to challenge the piezoelectric dominance in ultrasound imaging industry due to their wider bandwidth and excellent integration with electronics. We present a new fabrication technique for making flexible polymer-based CMUTs that is simple, inexpensive, and robust. The proposed technique includes forming CMUT cells through four lithography steps on a polyimide substrate, and then chemically releasing it from the silicon carrier (by a sacrificial layer) to reduce residual stress. The fabricated 1D, 8-element flexible array showed similar resonant response at 5.8 MHz on flat and curved surfaces without compromising functionality. Our finite element analysis also confirmed the minimal change in resonant frequency. The proposed device could be used for conformal ultrasound imaging of anatomical features.

Localization of normal modes in weakly coupled resonators is used in the recent MEMS sensors to achieve orders of magnitude improvement in sensitivity. It is known that the sensitivity ( $S$ ) of the modal amplitude ratio varies with the strength of the normalized coupling ( $\kappa$ ) as $S \propto \kappa^{-\textbf {1}}$ in the case of two identical coupled oscillators, and as $S \propto \kappa^{-\textbf {2}}$ in the case of three coupled oscillators with the middle oscillator of a much higher natural frequency. We have recently shown that an asymmetry measure $(\alpha)$ will also affect the sensitivity according to $S \propto \alpha^{-\textbf {1}}$ . Here, we prove, using an energy-based analysis, that in the general case of $n-2$ uniformly coupled oscillators chained between two terminal oscillators, $S \propto \alpha^{-\textbf {1}}{\kappa }^{\textbf {1}-{n}}$ , if the blocked resonance spectra of the embedded oscillators and the end oscillators are well-separated. We further show that coupled asymmetric oscillators will also enhance the operating linear range, besides the increased sensitivity when compared with their symmetric counterparts, in a three coupled oscillators system. Our sensitivity and linear range expressions, not based on a (small) perturbation approach, have a wider range of accuracy. These analytical results are validated through numerical computation in the illustrative cases of three and four cell resonator chains.

The authors report the fabrication of polymer MEMS transducers, without using any sacrificial layers, on flexible substrates. The elimination of sacrificial layers and the process overhead associated with them is achieved through maskless grayscale UV lithography of SU-8 photoresist, and results in a simplification of the overall fabrication process. Six batches, with a total of 60 cantilevers and 60 double- clamped beams, and three batches, with a total of 1500 circular membranes, have been fabricated on commercially available, 45 um Kapton® polyimide sheets coated with a 35um copper layer. The validation of the fabrication process has been done through functional characterization of the bi-directional electro-mechanical interface and robustness to mechanical bending. The test and measurement results of the fabricated microstructures validate a good design predictability (geometry error

A recently proposed method for measuring minute changes in capacitance based on weakly coupled resonators has been examined for its sensitivity with respect to unwanted resonant frequency changes. This sensitivity has been compared with the conventional capacitance measurement method based on the capacitance to frequency conversion. It has been analytically shown that both sensitivities are nearly equal but with opposite signs. This has led to a new hybrid capacitance measurement method to reduce the error by at least an order of magnitude. The analytical results have been validated by various simulations and experimental measurements.

Mobile devices and sensor networks advances have sharply increased the demand for inertial MEMS sensors with a direct digital output. This paper reports on the first implementation of a MEMS-based gyroscope system with all-digital control and readout, using sliding mode and bitstream processing for both the driving and sensing modes. The in-plane vibrating MEMS gyroscope, sensitive to out-of-plane external angular rates, was designed in a custom 50um SOI technology. A band-pass sliding mode control (SMC), equivalent to a digital PLL control, was used for electrically driving one of the resonant modes at its resonant frequency, and track its drift (due to environment variations). Simulations indicate a fast capture time in response to step variations (high tracking speed of 11,486 rad/s2) and small continuous tracking errors, below 0.0083 %. A regular (low-pass) sliding mode control was used for the sensing mode, in order to cancel its vibration and thus improve its linearity. The feedback loop action was proven to attenuate the displacement in the sensing mode by more than 100 times. The resulting bitstream output (that generates in the SMC loop the high-frequency cancelling electrostatic forces) contains the relevant information about the Coriolis force, and a bitstream synchronous demodulation technique is used to reconstruct the input angular rate to be measured, with a reconstruction error of ±0.2 rad/s. The overall system enables an easy future implementation on a MEMS+FPGA of a high-performance angular rate sensing microsystem with digital output.

Publicly available University College of Dublin Database (UCDDB) polysomnogram (PSG) patient cohort is analyzed and classified for archetypal sleep fragmentation in the presence of obstructive sleep apnea (OSA), the most severe sleep disorder. For comparison with Bianchi et al’s analysis of the Sleep Heart Health Study (SHHS) polysomnogram cohort, we first analyze sleep stage hypnograms statically by considering Wake After Sleep Onset (WASO), Rapid Eye Movement (REM), and grouped non-REM stages (Stages 1, 2, and 3/4) probabilistic distributions. We test the universality of Bianchi et al’s multi-exponential and power law models before proposing a third model with greater physical significance: Gaussian. In the absence of a control cohort without OSA, we separate the full PSG hypnogram into apneaic and ‘normal’ components. From this analysis, we observe the rapid decay of sleep stage durations as a result of apneaic events and the fragmentation of the natural 1.5 to 2 hour sleep cycle. To refine our model of the distinctive apnea ‘fingerprint’ on sleep stages, we consider a dynamic, one step Markov Chain model for WASO, REM, and separated NREM sleep stages (Stage 1, 2, 3, and 4) as this approach gives a better measure of sleep fragmentation. Our findings demonstrate that the presence of OSA alters both static and dynamic sleep characteristics which can feed into automatic detection of sleep stage identification and apnea event detection. Significantly, the probability of remaining in REM sleep is reduced from 81.0 percent during ‘normal’ sleep to 13.7 percent following an apneaic event. We conclude by outlining immediate next steps for improving the apnea detection model for integration with our at-home automatic sleep monitoring device. Such a device will augment data collected from oversubscribed sleep clinics to address the undersampling of sleep disorder patient monitoring.

This paper presents the analytical modeling, simulation and experimental validation of sensitivity, temperature variation and active controllability of MEMS geometric anti-spring (GAS) devices. Two models, the elasticity model and the thermal drift model, were proposed and analyzed, based on the study of asymmetrical and symmetrical geometric anti-spring structures. With the elasticity model, structural optimization led to analytical frequency-prestress design formula and a dedicated MEMS structure. An independent pre-stress and frequency shift effect is the result of thermal changes, so a thermal drift analytical model was built for the geometric anti-spring device, showing thermal sensitivities of and for the 3-spring and 4-spring devices, respectively. The analytical model was validated by both finite element analyses and experimental measurements. The designed devices (3-springs and 4-springs) were tested afterward in a dedicated setup, for both positive and negative electrostatically induced pre-stresses. Without electrical compensation, the thermal drift of the symmetrical 4-spring GAS device, for temperatures in the range to , is about 2138ppm, and it is reduced to only 8.35ppm when the electrostatic temperature compensation is active. Similarly, the asymmetrical structure has an uncompensated thermal sensitivity of its resonant frequency of 2254ppm in the temperature operation range, and it is reduced to 51.5ppm with electrical compensation within the easily controlled range of the temperature span, from to . As a result, although the benefits of the asymmetrical structure would lead to a higher sensitivity, trade-offs related to thermally-induced drift behavior and controllability also should be taken into consideration in the selection of the structural topology and application environment.

Heart rate (HR), the number of heart beats every minute, is the most relied upon vital sign for detecting health deterioration. It is no surprise, then, that the recording of HR is required in sleep studies as well. However, the standard monitoring method, the electrocardiogram (ECG), can be uncomfortable and intrusive, especially during sleep. Here, we present an HR monitoring system that uses the angular rate data from a single axis of a MEMS gyroscope to detect heartbeats. With a mean absolute error (MAE) and standard deviation of the absolute error (SDAE) values of -0.3505bpm and $+2.7167\mathrm{bpm}$ , in average, when our tests are compared with a reference ECG signal, we show that our system is accurate enough to track HR changes. Furthermore, the simplicity of our proposed approach makes it an ideal candidate for its implementation as a real-time, portable embedded system.

The ultrasonic transducer industry is dominated by piezoelectric materials. As an emerging alternative, capacitive micromachined ultrasound transducers (CMUTs) offer wider bandwidth, better integration with electronics, and ease of fabricating large arrays. CMUTs have a sealed cavity between a fixed electrode and a suspended metalized membrane. Manufacturing cost and sensitivity are limiting factors in current CMUTs that depend on the fabrication equipment and, especially, on the materials used. For widespread use of CMUTs, a much lower fabrication cost that uses inexpensive materials, which maintain or improve upon existing sensitivity, is needed. Herein, a new fabrication process is described for polymer-based CMUTs (polyCMUTs) using the photopolymer SU-8 and Omnicoat. The first ultrasound B-mode image of a wire phantom created with a 64-element linear array using synthetic aperture beamforming techniques is presented. A 12 VAC signal superimposed on a 10 VDC signal was used on the transmission side, and only a bias-tee, with no amplifiers, was used on the receiving side. The low operational voltage and high sensitivity of this device can be partially attributed to a pre-biasing condition on the membrane. By using a novel sacrificial layer combined with a top electrode embedded inside the membrane, we demonstrated that SU-8 can be used to manufacture CMUTs inexpensively. Moreover, the fabrication used relatively simple equipment, and the number of fabrication steps was reduced compared to traditional CMUT fabrication. This new fabrication process has the potential to increase the use of CMUTs in the ultrasound market, including the market for wearable transducers.

A novel pressure sensor is proposed exhibiting generative properties from displacement-induced ionic charge separation in gel electrolytes. A mechano-ionic or ‘piezo-ionic’ effect, in analogy to the well-known piezoelectric effect, is hypothesized to originate from a difference in mobilities between cationic and anionic species causing a localized ionic charge gradient upon application of pressure. This gradient can be detected as a voltage or current by using copper electrodes placed at the sides or at regular intervals along a surface of the gel. The voltage generated may be a result of the local concentration gradient induced by the deformation of the gel or perhaps is the result of some ions moving faster through the porous gel than others. In this work, ionic polymer gels based on Poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) co-polymer were synthesized in situ to incorporate an organic electrolyte consisting of bis(trifluoromethane)sulfonimide lithium salt in propylene carbonate. With two electrodes placed under the gel, the samples were subjected to a sinusoidal mechanical force while open circuit voltage was measured to determine the relationship between electrical signal and mechanical input. The voltages generated are 10’s of mV in magnitude at 1 kPa. Results suggest a maximum sensitivity of 25 μV/Pa at 10 mHz, comparable to the voltages expected in piezoelectric polymers such as PVDF (44 μV/Pa for similar dimensions). The non-aqueous, solid-state ionic gels presented in this work provide improved stability and is less prone to evaporation than its aqueous, hydrogel based counterpart. The new mechanism of sensing provides an alternative to the more rigid and less stretchable piezoelectric sensors.

Sleep disorders are a major health problem affecting more than 50 million people in the US alone. Sleep Apnea (SA) is by far the most common of these disorders, causing excessive sleepiness and diminished cognitive functions. Monitoring the respiratory effort is essential for SA detection. Conventional methods are limited to measuring only respiratory effort, and methods based on Inertial Measuring Units have been constrained to supine or standing/sitting positions. In this work, we propose a solution to such limitations, allowing the IMU to detect the respiratory effort on both supine and lateral recumbent positions, based on a sensor fusion algorithm. In addition, the body position is also obtained from the IMU data. Using the Pearson Cross-correlation Coefficient as a success metric, our results show correlation values ranging from 0.8550 to 0.9413 for various tests.

AB Introduction: Limited access to sophisticated technology and the unreliability of simple tools prevent accurate and reliable human standing balance assessments outside research laboratory settings. The goal of this study was to develop and validate a simple objective balance assessment tool that provides an accurate, reliable, and affordable alternative to currently available laboratory and clinical methods. Methods: Thirty healthy subjects were filmed performing the Balance Error Scoring System (BESS) while wearing inertial measurement units (IMU) measuring linear accelerations and angular velocities from seven locations of the body: forehead, sternum, waist, right and left wrist, and right and left shin. Each video was scored by four experienced BESS raters, whose mean scores were used to develop an algorithm computing objective BESS (oBESS) scores solely from IMU data. Interrater reliability and accuracy of oBESS scores were assessed using intraclass correlations (ICC). Results: Raters displayed low variability in scoring (ICC3,1 = 0.91). The oBESS was able to produce scores with accurate fit to raters (ICC3,1 = 0.92) and predicted individual BESS scores (ICC3,1 = 0.90) using data from one IMU placed at the forehead. oBESS was unable to produce accurate scores (ICC3,1 = 0.68) when using IMU data from the subset of conditions (firm surface only) used in popular concussion identification protocols. Conclusion: The oBESS can reliably predict total BESS scores in healthy subjects. Pending further validation, oBESS could represent a valid tool to assess balance by offering an objective and reliable alternative to the current scoring methods of the BESS.

In the new age of technology, internet and ever-improving communications many trends and fields have been appearing, such as smart phones and their applications, internet of things, renewable energy sources and smart buildings. The latter utilizes a number of aspects from the former, as the size of the buildings keeps growing, the engineers and designers aim to reduce energy consumption and ecological footprint, make the building safer and more sustainable. This has stimulated the growth of the field of sensor networks. This paper discusses a smart sensor network which utilizes Power over Ethernet, P.o.E., supplied by a Cisco Catalyst 4507R+E switch and cloud computing to provide an easily scalable and adaptable system that would be able to adapt easily to a wide array of applications and fit the demands of new trends. The system was tested on Raspberry Pi and BeagleBone microcontroller boards as sensor hubs, and uses DigitalOcean as the cloud computing service of choice. The server in this implementation acts as a user interface, front end, and as the console unit, back end. The system has demonstrated to have fast communication times of below 200ms in a cross-continental setting and able to provide fast processing times of under 1s.

In this paper, we present a disposable inkjet dispenser platform technology and demonstrate the Lab-on-a-Printer concept, an extension of the ubiquitous Lab-on-a-Chip concept, whereby microfluidic modules are directly integrated into the printhead. The concept is demonstrated here through the integration of an inkjet dispenser and a microfluidic mixer enabling control over droplet composition from a single nozzle in real-time during printing. The inkjet dispenser is based on a modular design platform that enables the low-cost microfluidic component and the more expensive actuation unit to be easily separated, allowing for the optional disposal of the former and reuse of the latter. To limit satellite droplet formation, a hydrophobic-coated and tapered micronozzle was microfabricated and integrated with the fluidics to realize the dispenser. The microfabricated devices generated droplets with diameters ranging from 150-220 μm, depending mainly on the orifice diameter, with printing rates up to 8000 droplets per second. The inkjet dispenser is capable of dispensing materials with a viscosity up to ∼19 mPa s. As a demonstration of the inkjet dispenser function and application, we have printed type I collagen seeded with human liver carcinoma cells (cell line HepG2), to form patterned biological structures.

We demonstrate large-area silicon-on-insulator ring resonators with Q values of about 2×10sup6/supat critical coupling and 3.6×10sup6/supfor heavily undercoupled conditions. A model has been developed to understand the impact of waveguide backscattering and subcomponent imperfections on the spectral response of our devices. The model predicts the appearance of signals at ports that would not have them under backscattering-free, ideal-power-splitting conditions. The predictions of our model are shown to match the phenomena observed in our measurements.

This paper describes the application of a novel band-pass sliding mode control (SMC) to the driving mode of MEMS-based resonators and resonant sensors (e.g. vibrating gyroscopes). The proposed technique relies on binary electrostatic actuation of the movable mass, dependent on the dynamics of the sliding/switching surface, in such a way that the generated actuation tracks possible changes in the mechanical resonant frequency induced by external factors (humidity, temperature, pressure, etc.). The core of the proposed adaptive method is the implementation in hardware of an adaptive behavioral reference model used by the controller, able to track the sensed changes in dynamics. The architecture has a low hardware complexity and is suitable for VLSI implementation, in addition to a robust tracking behavior for large variations in the parameters of the resonator (e.g. temperature-induced changes in the stiffness coefficient). Simulation results demonstrate the effectiveness of the proposed technique by maintaining the actuation of the system at its resonance frequency even in the presence of variations of the stiffness coefficient (step, linear)or of applied external forces (external acceleration and noise). Simulations results suggest that the novel SMC-based oscillator offers an advantageous alternative to more complex phase-locked loop (PLL) architectures, traditionally used for the driving of MEMS resonator structures.

Semiconductor ring resonators as the core components of instruments and devices have found applications in the areas of telecommunications and sensors. In this study, the feasibility of using ring resonators as solid-state angular rate sensors (gyroscopes) based on the Sagnac effect is assessed, and an extensive analysis of the optimal values of resonator length, coupling, and detuning is carried out, for the drop port of a double-bus ring, and for an all-pass, single-bus ring, for different values of propagation losses, consistent with different available technologies. We show that for both the all-pass and the drop-port configurations, optimally undercoupled rings show larger extinction ratios and, thus, better resolutions than critically coupled rings of the same length, contrary to our initial intuitive assumption that critically coupled rings should offer the best resolutions. Our analysis also shows that the ring resonator gyroscopes require a technology-constrained optimization, with the propagation loss as the main factor that hinders the resolution, and that determines the optimum values of all other parameters, namely length, coupling, and resonance detuning. According to our model, standard-chip-sized racetrack gyroscopes are suitable for rate- and tactical-grade applications for selected, currently feasible low propagation loss waveguides.

The attainable resolution of inertial sensors is ultimately limited by the cumulated noise level generated in both the mechanical domain (mechano-thermal noise) and the frontend of the electrical readout circuit, provided that deterministic errors, such as quadrature errors in the case of gyroscopes, are kept under control. Improving the resolution performance of MEMS structures mounts to being able to either increase the minimum detectable signal through an increased sensitivity, or to improve the signal-to-noise ratio (SNR). This paper reports on parametric amplification and damping employed in a MEMS gyroscope. Experiments confirm that parametric modulation through electro-mechanical coupling leads to both an increase in spectral selectivity and a reduction of the equivalent input noise angular rate (from 0.0046 ∘ / ( s Hz ) to 0.0026 ∘ / ( s Hz ) for a parametric gain of 5). In a more general analysis of a MEMS resonant structure, electro-mechanical parametric amplification decreases the mechano-thermal noise associated with the resonant mode motion – the equivalent input noise acceleration was diminished from 0.033 m s−2 to 0.022 m s−2 for a parametric gain of 5. Either signal amplification or an attenuation of undesired signal components can be achieved by tuning the phase difference between the driving force and the parametric coupling. Therefore, the technique can be applied as well to reduce the quadrature error signal, which strongly constrains the maximum gain of the sensing circuit. Our experiments show a 2.2 improvement factor in SNR using a parametric amplification with a gain of 25.

The pull-in time (tpi) of electrostatically actuated parallel-plate microstructures enables the realization of a high-sensitivity accelerometer that uses time measurement as the transduction mechanism. The key feature is the existence of a metastable region that dominates pull-in behavior, thus making pull-in time very sensitive to external accelerations. Parallel-plate MEMS structures have been designed and fabricated using a SOI micromachining process (SOIMUMPS) for the implementation of the accelerometer. This paper presents the experimental characterization of the microdevices, validating the concept and the analytical models used. The accelerometer has a measured sensitivity of 0.25 μs/μg and a bandwidth that is directly related to the pull-in time, BW = 1/2tpi ≈ 50 Hz. These specifications place this sensor between the state of the art accelerometers found both in the literature and commercially. More importantly, the resolution of the measurement method used is very high, making the mechanical–thermal noise the only factor limiting the resolution. The in-depth noise analysis to the system supports these conclusions. The total measured noise floor of 400 μg (100 μs) is mainly due to the contribution of the environmental noise, due to lack of isolation of the experimental setup from the building vibrations (estimated mechanical thermal noise of 2.8 μg/√Hz). The low requirements of the electronic readout circuit makes this an interesting approach for high-resolution accelerometers., ADI - Agência de Inovação, Fundação para a Ciência e a Tecnologia (FCT)

This paper reports on the simulation and characterization of a microelectromechanical system (MEMS) micromirror fabricated with PolyMUMPs. The overall diameter of the hexagonal micrimirror, including mirror plate and 3 supporting cantilevers fixed around, is 450um. A 3D model is built in finite element method (FEM) with COMSOL. Simulations of the elevated height of mirror plate, pull-in voltage and eigenfrequency of the micromirror are carried out. The static and dynamic performances of the fabricated micromirror are characterized by Veeco Optical Profiler and Polytek MEMS System Analyzer. The comparison between measurement and simulation exhibits good concordance. Surface topography measurement shows the elevated height and stress-induced concave deformation of mirror plate almost the same scale as demonstrated in FEM simulation. The Pull-In voltages are measured to be around 32V in current-voltage curve which is almost the same as in FEM simulation with one electrode biased. The fundamental resonant frequency is measured to be 4.3k Hz in torsional motion and 4.9k Hz in piston motion.

This paper investigates the concept of tiltable ultrasonic transducers, and their application in focusing and steering in a transducer array. Results of simulated imaging processes suggest that physical focusing and steering with tiltable transducers is promising in reducing grating lobe and side lobe artifacts, and preserving the beam power, especially when steering to large angles. We propose that one embodiment of the tiltable transducers can be adaptive capacitive micromachined ultrasonic transducers (CMUTs) modeled as clamped plate radiators. By applying different levels of electrical field on their split electrodes, one can adjust the shape and orientation of the adaptive CMUTs adaptively and dynamically, creating a tilted effect in the beam direction. The feasibility of using adaptive CMUTs to implement tiltable transducers is studied using finite element modeling (FEM) and analytical modeling. Experimental measurements of the tilted behavior of fabricated adaptive CMUTs are also provided. Possible applications of the tiltable transducers, including spatial compounding, high intensity focused ultrasound (HIFU), adaptive imaging, and harmonic imaging, are discussed.

This paper proposes an analytical capacitive micromachined ultrasonic transducer (CMUT) model that couples three physical domains using plate vibration and radiation theories. The model accounts for the spatial distribution of the normal deflection over the CMUT cell membrane. A mode superposition expression is used to capture the complicated flexural-plate-like movement. We compare the results of analytical calculations using the proposed plate model with those of finite-element modeling, together with the analytical results of the piston-like models. This approach shows promise for more detailed and convenient physical modeling of CMUTs, which could lead to new ways of designing and controlling them.

The experimental evaluation of damping-improved parallel-plate geometries is reported in this paper. An improved damper geometry with air channels was developed to address contradictory design constraints: large sensing parallel-plate area is desirable for a significant readout capacitance as well as reduced damping coefficient. Damping coefficients were measured at different gaps in conventional parallel-plates MEMS and in parallel-plates with air channels. The inertial masses of the fabricated structures were pulled-in and released. From the return to rest position trajectory, the damping coefficients, at each point, were extracted. Results show a significant damping decrease in parallel-plates with air channels without visible reduction in the capacitance value., Fundação para a Ciência e a Tecnologia (FCT)