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Nowadays, the piezoelectric transduction mechanism has a great concern to be used in the (micro-electromechanical systems) MEMS microphones. In piezoelectric microphones, the thickness, length, width of the piezoelectric and electrode materials are key parameters that need to be optimized in the design loop. The sensitivity is also another vital design factor for MEMS microphones. One common scenario in modeling the sensitivity is to build an electrical equivalent model from lumped components in any simulator. This approach generally requires specialist design expertise and substantial time to build a complete equivalent model. In this paper, a powerful simulation platform to design high-performance cantilever piezoelectric MEMS microphones with sensitivity estimation has been presented. This simulation platform, called MEMS microphone optimizer platform (MMOP), can predict a wide range of key issues related to the successful design of a MEMS Microphone such as the optimum values of piezoelectric material thickness, electrode material thickness, and the length of a cantilever. MMOP offers also the capability to simulate sensitivity directly from the input parameters of the designed model. To validate the proposed simulation platform, a real model of a cantilever MEMS microphone has been studied. In the performed simulations and analysis, sweeping dimensions in micrometer have been considered to predict the best performance. In the proposed model, Aluminum nitride (AlN) and molybdenum (Mo) were utilized as the piezoelectric material and electrode materials, respectively. A high agreement has been found between the theoretical results and the output of the MMOP platform. The platform opens the door for a fast optimized design with accurate results. Finally, MMOP enables a designer to simulate key issues that are specific to cantilever MEMS microphones, including optimized thickness values and predicted sensitivity.

Piezoelectric MEMS microspeakers are promising candidates for miniaturized speakers, such as for in‐ear applications. Using lead‐free scandium doped aluminium nitride (ScAlN) thin film instead of lead zirconium titanate helps these speakers to be environmental friendly, CMOS compatible and potentially more linear. The piezoelectric coefficient of ScAlN is higher than undoped AlN, which leads to improved performance of MEMS actuators including speaker chips. The design of piezoelectric MEMS ScAlN speaker based on four triangular cantilevers is proposed. The design in this work has been verified by finite element method simulation. The displacement and sound pressure level are 39 μm and 56 dB, respectively. This MEMS loudspeaker has small size and simple structure. The model opens the door also to further optimization for higher energy efficiency and higher acoustic performance based on lead‐free ScAlN thin film.

This paper reports the achievement of a mass balanced condition in a low-Q weakly coupled MEMS resonator array for ultrafine aerosol particulate sensing. The mass balancing technique enables the lifetime extension of such real-time particulate sensors without employing any wet or dry-cleaning techniques to remove particles from the resonators. This mass balancing is demonstrated for both the flexural and bulk modes of the same coupled resonator array occurring at ∼54kHz and ∼2.53MHz, respectively. This system also demonstrates for a degree of passive environment immunity to temperature effects by using an amplitude ratio output metric. The Q factor of the coupled MEMS resonator system do not degrade substantially with increased particulate loading.

International audience; Lead zirconate titanate Pb(Zr,Ti)O 3 (PZT) is a well know ferroelectric material with excellent piezoelectric properties, namely large piezoelectric coefficients, low leakage current and reliable performance, which makes it very suitable as an actuator material in Micro-ElectroMechanical Systems (MEMS). The performance of piezoelectric MEMS is, however, strongly dependent on the film quality. In the present work, the epitaxial growth of PZT is desired as it can help to reduce high-frequency losses, to allow for larger electromechanical coupling and to increase the final device sensitivity. We used an epitaxially grown conductive oxide bottom electrode, namely 45 nm thick La 2/3 Sr 1/3 MnO 3 (LSMO) films, deposited on SrTiO 3 buffered (001) silicon substrates using a combination of pulsed laser deposition and reactive molecular beam epitaxy techniques. The 500 nm thick c-axis oriented PZT layers were deposited at 600°C by magnetron sputtering on the LSMO films on STO/Si (001). The piezoelectric and ferroelectric properties of the PZT layers were studied by PiezoForce Microscopy on as-grown PZT films and Polarization versus Electric field measurements on samples covered with Pt top electrodes. The PZT films exhibited good piezoelectric and ferroelectric properties with a remanent polarization higher than 20 µC·cm −2 , which makes them suitable for the fabrication of piezoelectric MEMS based on doubly-clamped LSMO suspended structures.

Piezoelectric MEMS (Micro-Electro-Mechanical Systems) are used in many applications now a day’s including the diagnosis of diseases.COVID-19 is a pandemic recently affecting the entire world. Various techniques for detection are being used to date. Paper presents a simulation-based piezoelectric MEMS detection method for the virus, which is fast, portable, cost-effective, require less amount of sample, reliable, and can diagnose the stage for SARS-CoV-2(Severe acute respiratory syndrome corona virus 2) from the first day of virus infection. The design and analysis of cantilever-based MEMS biosensor is done COMSOL Multiphysics. Three cantilevers are used in the design, one each for viral load, IgM, and IgG. The bio-molecular reaction on the cantilever increases the mass at the end, changing the electrical and mechanical properties in the cantilever. Piezoelectric material generates the voltage proportional to the mass applied. From the values of voltage obtained from three cantilevers, the infection stage for symptomatic and asymptomatic can be diagnosed. Results show a linear relationship between the load applied and voltage generated. The proposed biosensor has a mass sensitivity of 20 copies /ml.

In this paper we propose a heart sound monitoring device which consists of a piezoelectric MEMS acoustic sensor, a low noise amplification circuit, and silicone polymers with an air-cavity. The piezoelectric MEMS acoustic sensor is composed of a 6by7 aluminum nitride (AlN) membrane array. We verify the potential of the proposed device to diagnose heart diseases by using six different types of simulated heart sounds. Furthermore, the heart sound of a healthy human subject at rest and after exercise, with and without noise are also tested. Both the S1 and S2 sounds of the heart are easy to recognize according to the measured waveforms, indicating that the proposed device has the potential of fitness monitoring and heart disease diagnosis.

We report on a piezoelectric micromachined ultrasonic transducer (PMUT) driven in a nonlinear regime, generating chaotic amplitude modulated ultrasonic waves. At large enough drives, the PMUT enters in the Duffing regime which opens a hysteresis with two available states. By modulating the frequency of the driving signal, the system may switch between both states, and selecting the appropriate modulation frequency enables to enter in the chaotic regime. The chaos is then imprinted as a modulation of the PMUT’s amplitude. We characterize this regime in the three accessible domains: electrical, mechanical and acoustic, and demonstrate they are fully correlated. We then focus on the generated acoustic signals and demonstrate that the chaotic modulation propagates according to the PMUT’s linear regime. Remarkably, the detected acoustic waves are strongly correlated to the on-chip piezoelectric measurements, regardless of the acoustic beam profile. The frequency spectrum of the chaotic modulation spreads around the ultrasonic carrier, mimicking a noise modulated carrier signal. We exploit this property for jamming applications where the chaotic PMUT is used to mask surrounding acoustic waves. Unlike most jamming applications, our approach does not require driving signals with a broad frequency spectrum, the noisy pattern arising directly from the structure’s dynamics. Using two PMUTs, one in the linear and the other in the nonlinear regime, we realize a proof-of-concept where the ultrasound generated by the first PMUT is drowned out by the chaotic PMUT signal. We demonstrate that the carrier frequency of the jamming PMUT does not need to match perfectly the one of the linear PMUT. This chaos generation is generic and could be adapted to any PMUT, and thanks to the rich frequency spectrum of the chaotic modulation, the frequency of the signal to jam does not need to be precisely known.

Neben kapazitiven und piezoresistiven Elementen für sensorische und aktorische Anwendungen ist die Piezoelektrizität ein weiterer etablierter Wandlungsmechanismus in mikroelektromechanischen Systemen (MEMS), welcher in den letzten Jahren zunehmendes Interesse erfährt. Dazu werden für gewöhnlich piezoelektrische Materialien wie die Piezokeramiken Blei-Zirkonat-Titanat (PZT) oder Aluminiumnitrid (AlN) verwendet. Allerdings sind diese Materialien typischerweise sehr steif und besitzen ein hohes Elastizitätsmodul. Um neuartige flexible und weiche MEMS-Anwendungen zu ermöglichen, wurden in dieser Arbeit ferroelektrische bzw. piezoelektrische Polymere, wie das Copolymer aus Vinylidenfluorid und Trifluorethylen (P(VDF-TrFE)), näher untersucht. Synthetisierte ferroelektrische Polymerdünnfilme wurden detailliert auf ihre strukturellen, mechanischen, elektrischen und elektromechanischen Eigenschaften analysiert. Ferroelektrische Polymere haben ein niedriges Elastizitätsmodul und zeigen eine starke piezoelektrische Aktivität, womit diese prädestiniert für weiche und flexible MEMS-Anwendungen sind. MEMS basierend auf ferroelektrischen Polymeren wurden durch die Anwendung eines angepassten Silizium-MEMS-Technologieprozesseses erreicht. Insbesondere wurden MEMS-Cantilever hergestellt und analysiert. Die piezoelektrischen und elektrostriktiven Eigenschaften des ferroelektrischen Polymerfilms wurden ausgenutzt, um verschiedene Schwingungsmoden des MEMS-Cantilevers anzuregen. Diese weichen Polymer-MEMS-Cantilever stellen eine sehr vielversprechende Basis für neuartige AFM-Sonden dar, deren Schwingungszustand elektrisch verändert und ausgelesen werden kann. Das bevorzugte Anwendungsgebiet liegt in der Analyse von weichen oder biologischen Proben. Darüber hinaus wurde in dieser Arbeit festgestellt, dass für die derzeitig verwendeten Hochgeschwindigkeits-AFM-Sonden eine Leistungsgrenze in Bezug auf hohe Resonanzfrequenz und niedriger Federkonstante erreicht ist. Aus dieser Erkenntnis wurde ein neuartiges Konzept für Hochgeschwindigkeits-AFM-Sonden entwickelt. Durch die Kopplung zweier Mikrostrukturen, einer plattenförmigen und einer balkenförmigen Mikrostruktur, werden AFM-Sonden vorgestellt, die sowohl eine hohe Resonanzfrequenz als auch eine niedrige Federkonstante aufweisen. Diese neuartigen AFM-Sonden bieten die Möglichkeit, die Grenzen der derzeitigen Hochgeschwindigkeits-AFM-Anwendungen substantiell zu erweitern, Besides capacitive and piezoresistive elements for sensing and actuating purposes, piezoelectricity is another well-established transducer mechanism in microelectromechanical systems (MEMS), experiencing increasing interest in recent years. Piezoelectric materials like the piezoceramics lead zirconate titanate (PZT) or aluminium nitride (AlN) are commonly used. However, these materials are typically very stiff and possess a high elastic modulus. In order to enable novel flexible and soft MEMS applications, ferroelectric or piezoelectric polymers, such as the copolymer of vinylidene fluoride and trifluoroethylene (P(VDF-TrFE)), were investigated in detail in this thesis. To that end, synthesised ferroelectric polymer thin films were analysed regarding their structural, mechanical, electrical and electromechanical properties. Ferroelectric polymers possess a low elastic modulus and a strong piezoelectric response and, thus, are predestined for soft and flexible MEMS applications. Ferroelectric polymer MEMS were achieved by applying a tailored silicon MEMS technology process using standard microfabrication techniques. In particular, MEMS cantilevers were fabricated and analysed. The piezoelectric and electrostrictive transducer mechanism of the ferroelectric polymer film was exploited to excite several vibration modes of a MEMS cantilever. These soft polymer MEMS cantilevers represent a promising platform to enable self-actuating and self-sensing AFM probes for the imaging of soft or biological samples. Furthermore, it was demonstrated in this work that current state-of-the-art high-speed AFM probes reached a performance limit when requesting both high resonance frequency and low spring constant. Therefore, a novel concept for high-speed AFM probes was developed. By coupling two microstructures, a plate-type and a beam-type microstructure, AFM probes are accessible that combine both a high resonance frequency and a low spring constant. These novel AFM probes provide the ability to push the limits of current high-speed AFM applications.

A commercially produced monocrystalline-like epitaxial PZT film is described for piezoelectric MEMS applications. Films with a thickness of $1\ \mu \mathrm{m}$ to $2\ \mu \mathrm{m}$ exhibit a typical transverse piezoelectric d31 coefficient of −185 pm/V, relative dielectric permittivity of 430 and dielectric loss of 0.015. These films are commercially available for piezoelectric MEMS device development and production.

This paper successfully demonstrates the potential of weakly coupled piezoelectric MEMS (Micro-Electro-Mechanical Systems) gravimetric sensors for the detection of ultra-fine particulates. As a proof-of-principle, the detection of diesel soot particles of 100 nanometres or less is demonstrated. A practical monitoring context also exists for diesel soot particles originating from combustion engines, as they are of serious health concern. The MEMS sensors employed in this work operate on the principle of vibration mode-localisation employing an amplitude ratio shift output metric for readout. Notably, gains are observed while comparing parametric sensitivities and the input referred stability for amplitude ratio and resonant frequency variations, demonstrating that the amplitude ratio output metric is particularly suitable for long-term measurements. The soot particle mass directly estimated using coupled MEMS resonators can be correlated to the mass, indirectly estimated using the condensation particle counter used as the reference instrument.

Objective: This paper discusses analytically and by simulation, a novel disk and ring-shaped piezoelectric micromechanical acoustic resonators in which asymmetric Lamb wave mode is induced in a thin-film aluminum nitride (AlN)-on-silicon structure. Method: The piezoelectric resonators are designed and simulated at two-port state by the aid of FEM tool. An analytical investigation is carried out in order to study the propagation of asymmetric lamb wave in a cylinder structure. Circular electrodes are utilized for excitation of intended order of asymmetric acoustic Lamb wave in the structures. Due to the significance of feedthrough capacitances in the piezoelectric MEMS resonators in high-frequency applications, these capacitances are calculated and extracted. Several electrodes and tethers configurations are introduced and simulated by FEM simulation in order to study distortion of resonator structures. Result: Stress-free nodal zones close to the resonators outer edge are identified and support tethers, which are used to anchor the resonators, are connected to those points by applying the notch method. Connecting anchoring tethers to stress-free nodal zones considerable decreased tether deformation leading to lower loss for resonators. The prototype models of structures work at 307 MHz and 318 MHz for the disk-shaped and ring-shaped resonators, respectively. Numerous transient and harmonic analysis have been carried out in order to study resonators behavior at the fundamental mode and their spurious electrical response. Conclusion: The proposed structures in this paper can be a promising choice for different applications ranging from RF filter, RF oscillators, RF micromachined circuits and physical and biochemical sensors.

Physiological mechano-acoustic signals play a pivotal role in medical diagnosis and fitness monitoring. Mechanical waves generated by natural physiological activities such as myocardial contraction, and vocal fold vibration, propagate through the tissues and fluids of the body and reveal characteristic signals of these events. Conventional methods such as stethoscope and electrocardiography (ECG) are not suitable for wearable mode and continuous monitoring. In this paper, we propose a wearable physiological sounds sensing device to monitor heart sound and detect speech and voice with high accuracy. The device consists of a MEMS (microelectromechanical systems) acoustic sensor and a low-noise amplification circuit, and both of them are packaged by silicone polymers with an air cavity to achieve conformal contact with human skin. The proposed device has advantages of light weight, sweatproof capability, resistant to noise and good stability. The wearable device has great potential in clinical diagnosis, healthcare, human-machine interaction and many other applications.

To solve the problem of a single function encountered by wearable electronic devices, a multifunctional wearable piezoelectric MEMS device is presented, which performs motion monitoring and disease and health warning according to respiratory frequency, functions as an earphone based on the inverse piezoelectric effect of the PZT film. The rigid-flexible coupling sealed vibration membrane allows the piezoelectric MEMS device to eliminate acoustic loss or avoid airflow loss. By placing the device in a simple wearable mask, the inactive, walking, and running states may be possible to be recognized and monitored through respiratory frequency. In the inactive state, the device can identify diseases when abnormally fast or slow respiration occurs. By placing the device in the surgical mask when going out, an early warning of something affecting lung health can be obtained by excessive respiration frequency when wearing the mask for too long. Moreover, the device can also be utilized as an earphone. Higher than 55 dB SPL can be obtained in the full frequency range of the human ear under 2 V, meeting the basic needs of people's hearing. This simple strategy represents a significant step toward future applications of the wearable piezoelectric MEMS device due to its portability, multifunctioning, convenience, and mass production.

This paper presents piezoelectric MEMS microphone arrays for automatic detection of wheezing in lung sound. Very high unamplified sensitivities of 36.3 – 78.2 mV/Pa have been obtained at the resonant frequencies of the microphone array between 200 and 500 Hz where wheezing is typically prominent. Consequently, the acoustic feature of wheezing was distinguished better in both time domain and frequency domain in comparison with a flat-band reference microphone. With this advantage, as high as 97.44% identification accuracy of lung sounds with and without wheezing was achieved, while the same algorithm based on a commercial reference microphone yielded 89.74% accuracy.

The discovery of enhanced piezoelectricity in solid solutions of AlN and ScN is certainly one of the most important events in piezoelectric MEMS. As compared to pure AlN, it brought a crucial factor 2 to 3 improvement in a number of figures of merit governing the performance of MEMS devices. The aim of this contribution is to give a short overview on actual topics in processing, properties, and applications in RF filters and sensors.

We present a small-scale piezoelectric MEMS micromirror, with resonant frequencies above 300 kHz for 1D scanning. The device is intended for higher frequency operation by reducing the scale of existing designs, and was fabricated using a multi-user silicon-on-insulator process. The performance of the mirror for addressing points along one axis was demonstrated using a free-space optics experimental setup.

Piezoelectric MEMS resonators based on advanced aluminum nitride thin films are a promising and versatile technology platform to tackle a multitude of sensory challenges. In this talk, we will give an overview on recent achievements in this field focusing on potential applications for e.g. sensing the viscosity and density of liquids and serving as integrated transducers to push the performance of buckled membranes.

This paper presents a self-deformable varifocal MEMS mirror for a focus-tunable MEMS scanner. Piezoelectric actuator was monolithically integrated on a 4 mm-diameter mirror, and its focus changed from −120 mm to +140 mm according to the applied DC voltage. The maximum optical scanning angle of the proposed scanner was 26.2°, which meets the demands of high-resolution laser scanning applications.

Quality factor (Q) is an extremely important parameter for the practical applications of micro-electromechanical systems (MEMS) resonators. Single optimization is difficult to achieve the high-performance MEMS resonators. This paper reports a strategy of triple-order optimization for high-performance piezoelectric MEMS resonator by resonant body parallel connection, suspended frame structure and phononic crystals (PnC). Firstly, according to the Butterworth Van Dyke (BVD) equivalent circuit model, the topologies structure of resonator was comprehensively studied and the three resonant bodies parallel connection was proposed to lower the motional impedances, while the anchor loss will rise due to the number of tethers increased. Secondly, the suspended frame structure was utilized to reduce the number of tethers in parallel-type resonators to suppress the anchor loss. Thirdly, the PnC structure was proposed to further realize high-Q by preventing the leakage of acoustic energy from resonant body to substrate via tethers. Finally, the Q of the proposed resonator was obtained by using finite-element-analysis (FEA) simulation, which revealed a 3.3fold enhancement (i.e. Q u = 9318.0) compared with the conventional resonator (i.e. Q u = 2799.6). In the meantime, the motional resistance and insert loss have also been significantly optimized.

Doped lead–zirconate–titanate (PZT) thin films are preferred for the development of micro–electro–mechanical systems (MEMS)-based acoustic sensors because of their inherent higher dielectric and piezoelectric coefficients. Patterning process is used to develop such MEMS devices which is highly complex even for undoped PZT thin films; therefore, the problem is further cumbersome for doped PZT thin films due to the presence of added dopant elements and their associated chemistry. This paper presents patterning of strontium (Sr) and lanthanum (La) co-doped PZT thin film (PSLZT) deposited on platinized silicon substrate using wet and dry etching processes for fabricating a diaphragm structure with thickness of 15–25[Formula: see text][Formula: see text]m and diameter of 1.4–2[Formula: see text]mm, suitable for acoustic sensing applications. The effects of various etching conditions have been studied and the results are reported. It is found that the dry etching is the most suited process for realizing the piezoelectric MEMS structure due to its higher etching resolution. An appreciable etching rate of 260–270[Formula: see text]nm/min with smooth vertical sidewalls is achieved. The silicon diaphragm with patterned PSLZT thin film is found to retain more than 80% of its dielectric and piezoelectric coefficients and has a resonance of 1.43[Formula: see text]MHz.

MEMS speakers are attracting more and more interests due to their potential applications in portable and wearable electronics. However, insufficient sound pressure level (SPL) associated with the reduced size is a main challenge for most existing MEMS speakers. This paper presents the design, fabrication and characterization of a high-SPL piezoelectric MEMS speaker based on high-piezoelectric constant ceramic PZT. The ceramic PZT, bonded on an SOI substrate, was thinned down to only 5 μm successfully. The microfabricated piezoelectric MEMS speakers exhibited significantly enhanced SPLs. At a distance of 10 mm, a maximum SPL of 119 dB was achieved in open air by such a single MEMS speaker with a footprint of 6.7 mm × 6.7 mm under a low driving voltage of only 10 Vpp. The SPLs at frequencies as low as 400 Hz still reached over 90 dB. These SPLs are comparable to those of conventional loud speakers or micro-speaker arrays with significantly larger sizes.

The article provides to the reader a brief of the piezoelectric materials characteristics and their possibilities in biomedical microdevices development. The first section of this article presents the basics of piezoelectric MEMS. The research is focused on microgrippers since this technology is widely used in biomedical applications. The second section of this article present a review of both the direct and inverse piezoelectric effects and the piezoelectric coupling formulation used for modelling biomedical microgrippers. An analysis of piezoelectric gripper based on finite-element calculations is presented in which the fundamental electroelastic equations governing piezoelectric media are solved numerically. A study on how different geometries, different piezoelectric materials and even different mesh densities influences the performances of the microgripper are described in the last section of this article. The experimental results confirm their efficiency and demonstrate that the piezoelectric microgrippers are well suited in biomedical applications.

For distributed sensing, local power sources are of interest. [...]

A flexible simulation platform to design new piezoelectric MEMS (micro-electro-mechanical systems) microphones with signal-to-noise ratio (SNR) evaluation is presented. The platform is made of two blocks: a multiphysical FEM model, in order to study the acoustic, mechanical and electrical behavior of the MEMS structure, and an equivalent electro-mechanical-acoustic lumped-element model, which allows studying the microphone system, i.e. the MEMS-package-ASIC interaction. The platform gives precise estimation of sensitivity and SNR, key parameters of a microphone.

Electromechanical transducers that utilize the piezoelectric effect have been increasingly used in micro-electromechanical systems (MEMS) either as substrates or as thin films[...].