Search

According to upper echelons theory, firms' strategic decision-making is, to a great extent, driven by the mindsets of the managers. Focusing on the role of the Chief Executive Officer (CEO) coopetitive mindset, which reflects the CEO's favorable perception of simultaneously competitive and cooperative relationships and the willingness to pursue opportunities for accessing complementary assets and managing complicated relationships in positive ways, this research attempts to fill an important gap in the growing body of literature by examining the human-side antecedents of firm coopetition, as well as its boundary conditions. Using a two-phase survey of 780 Chinese firms, we found that firms with CEOs who have more coopetitive mindsets are more likely to adopt coopetition alliances for innovation. In addition, the relationship between CEO mindsets and firm coopetition is contingent on different levels of executive job demand. Specifically, higher levels of innovation performance challenge, technological uncertainty, and regional intellectual property protection incompleteness strengthen the impact of CEO mindsets on firm coopetition alliances. This research enriches our understanding of the micro-foundation of coopetition by considering the role of CEOs. We also contribute to the upper echelons theory by depicting how executive job demands interactively moderate the impact of CEO mindsets in the contexts of firms' coopetition for innovation. Moreover, this study provides enlightening implications for ongoing managerial practice. [ABSTRACT FROM AUTHOR]

Acoustically actuated magnetoelectric (ME) antennas utilize acoustic wave resonance to complete the process of receiving and transmitting signals, which promotes the development of antenna miniaturization technology. This paper presents a bilayer magnetostrictive/AlN ME laminated antenna. The proposed laminated antenna uses the FeGa/FeGaB bilayer materials as magnetostrictive materials, which combine the advantages of soft magnetic properties of FeGa and the low loss of FeGaB. First, multiphysics modeling and analysis are performed for the proposed ME laminated antenna by finite element method (FEM). The positive/inverse ME effects and the influences of the volume ratio of the FeGa/FeGaB bilayer on the antenna performance are studied. The results show that the output voltage and ME coefficient of the FeGa/FeGaB bilayer magnetostrictive material with a volume ratio of 1:1 are 3.97 times and 195.8% higher than that of the single FeGaB layer, respectively. The eddy current loss is 52.08% lower than that of single-layer FeGa. According to the surface equivalence principle, the far-field radiation process is simulated. The results show that the gain of the ME antenna is 15 dB larger than that of the same-size micro-loop antenna, and the gain of the ME antenna is about −44.9 dB. The improved performance and magnetic tunability of the proposed bilayer magnetostrictive materials make ME antennas excellent candidates for portable devices and implantable medical devices. [ABSTRACT FROM AUTHOR]

In robotic‐assisted minimally invasive surgery (RMIS), non‐sentient surgical instruments make it impossible for surgeons to perceive operational force during the procedure. To facilitate surgeons with force telepresence during surgery, a highly integrated MEMS‐based piezoresistive 3D force sensing module, which is composed of a MEMS‐based piezoresistive sensor chip, an encapsulation cap with miniature pyramids, and a top elastic layer, is demonstrated. This innovative combined construction allows for rapid replacement of elastic layers with different thicknesses and different Young's modulus, so as to realize an adjustable sensitivity and measurement range for different surgeries. By replacing the elastic layer, the same amount of change in resistance can be achieved for external force of 3 and 10 N in the Z‐axis; the sensitivity in X‐ and Y‐axes can be increased by a maximum of eight and seven times, respectively. Meanwhile, miniature size enables it to be integrated into various surgical instruments' tip. Experimental demonstrations involving palpation simulated nodule detection of kidney, ex vivo puncture, and threading forces estimation of tissue‐mimicking are conducted to validate the effectiveness of adjusting sensitivity and range. This sensing module is potentially a promising solution for low‐cost and versatility to surgical instruments, which can facilitate unification of force‐sensing/intelligent surgical instruments. [ABSTRACT FROM AUTHOR]

Transit-time ultrasonic flowmeters (TTUFs) are among the most widely used devices for flow measurements. However, traditional TTUFs are usually based on a bulk piezoelectric transducer, which limits their application in small-diameter channels. In this paper, we developed a miniaturized TTUF based on scandium-doped aluminum nitride (ScAlN) piezoelectric micromachined ultrasonic transducers (PMUTs). The proposed TTUF contains two PMUT-based transceivers and a π-type channel. The PMUTs contain 13 × 13 square cells with dimensions of 2.8 × 2.8 mm2. To compensate for the acoustic impedance mismatch with liquid, a layer of polyurethane is added to the surface of the PMUTs as a matching layer. The PMUT-based transceivers show good transmitting sensitivity (with 0.94 MPa/V surface pressure) and receiving sensitivity (1.79 mV/kPa) at a frequency of 1 MHz in water. Moreover, the dimensions of the π-type channel are optimized to achieve a measurement sensitivity of 82 ns/(m/s) and a signal-to-noise ratio (SNR) better than 15 dB. Finally, we integrate the fabricated PMUTs into the TDC-GP30 platform. The experimental results show that the developed TTUF provides a wide range of flow measurements from 2 to 300 L/h in a channel of 4 mm diameter, which is smaller than most reported channels. The accuracy and repeatability of the TTUF are within 0.2% and 1%, respectively. The proposed TTUF shows great application potential in industrial applications such as medical and chemical applications. [ABSTRACT FROM AUTHOR]

This Letter reports on microwave-induced thermoacoustic imaging utilizing a multi-cell aluminum scandium nitride (AlScN) piezoelectric micromachined ultrasonic transducer (PMUT). Thermoacoustic signals are induced by microwave pulses and then detected by the ultrasonic transducer. It carries biological information, thus enabling noninvasive clinical diagnosis. Our AlScN PMUT device was characterized and experimented to show that it could significantly improve the imaging of the biological sample, decreasing the mean square error by up to 72%, which benefits from a 2.96 times larger detection angle of thermoacoustic signals compared to commercial ultrasonic transducers. The miniaturized and high-performance PMUT devices have the potential to be applied to clinical or personal diagnosis and monitoring equipment. [ABSTRACT FROM AUTHOR]

Thin film-based surface acoustic wave (SAW) technology has been extensively explored for physical, chemical, and biological sensors. However, these sensors often show inferior performance for a specific sensing in complex environments, as they are affected by multiple influencing parameters and their coupling interferences. To solve these critical issues, we propose a methodology to extract critical information from the scattering parameter and combine the machine learning method to achieve multi-parameter decoupling. We used the AlScN film-based SAW device as an example in which the highly c-axis orientated and low stress AlScN film was deposited on silicon substrate. The AlScN/Si SAW device showed a Bode quality factor value of 228 and an electromechanical coupling coefficient of ∼2.3%. Two sensing parameters (i.e., ultraviolet or UV and temperature) were chosen for demonstration, and the proposed machine learning method was used to distinguish their influences. Highly precision UV sensing and temperature sensing were independently achieved without their mutual interferences. This work provides an effective solution for decoupling of multi-parameter influences and achieving anti-interference effects in thin film-based SAW sensing. [ABSTRACT FROM AUTHOR]

This paper reports on an aluminum nitride (AlN) piezoelectric micromachined ultrasound transducer (PMUT) array for photoacoustic (PA) imaging, where the high-order resonance modes of the PMUT are utilized to improve imaging resolution. A flexural vibration mode (FVM) PMUT is fabricated and applied in a photoacoustic imaging (PAI) system. Specifically, the microelectromechanical system (MEMS)-based PMUT is suitable for PA endoscopic imaging of blood vessels and bronchi due to its miniature size and high sensitivity. More importantly, AlN is a nontoxic material, which makes it harmless for biomedical applications. In the PAI system, the AlN PMUT array is used to detect PA signals, and the acousto–mechanical response is designed and optimized at the PMUT's fundamental resonance. In this work, we focus on the high-order resonance performance of the PMUT PAI beyond the fundamental resonance. The acoustic and electrical responses of the PMUT's high-order resonance modes are characterized and analyzed. The fundamental and three high-order resonance bandwidths are 2.2, 8.8, 18.5, and 48.2 kHz. Compared with the resolution at the fundamental resonance mode, the resolutions at third- and fourth-order resonance modes increase by 38.7% and 76.9% in a phantom experiment. The high-order resonance modes of the AlN PMUT sensor array provide higher central frequency and wider bandwidth for PA signal detection, which increase the resolution of PAI compared to the PMUT working at the fundamental resonance mode. [ABSTRACT FROM AUTHOR]

In this paper, a flexible piezoelectric micromachined ultrasonic transducer (PMUT) based on Scandium (Sc)-doped Aluminum Nitride (AlN) film was designed and modeled by the three-dimensional finite element method (3D-FEM). The resonant frequency of 218.1 kHz was reported. It was noticeable that a high effective electromechanical coupling coefficient (k2eff) of 1.45% was obtained when a combination of a flexible PI and a thin Si layer was used as the PMUT supporting structure layer. Compared with a pure Si supporting layer counterpart, the coupling coefficient had been improved by 110.68%. Additionally, the increase of Sc doping concentration in AlN film further enhanced the device electromechanical coupling coefficient and resulted in an improvement for transmitting/receiving sensitivity of the proposed flexible PMUT. When the doping concentration of Sc reached 30%, the emission sensitivity was as large as 1.721 μm/V, which was 2.86 times greater than that of conventional AlN film-based PMUT. The receiving sensitivity was found to be 2.11 V/KPa, which was as high as 1.23 times the performance of an undoped device. Furthermore, the bending simulation result showed that the proposed flexible PMUT device can maintain a good mechanical stability when the bending radius is greater than 1.5 mm. The simulation of sound field characteristics demonstrated that the flexible PMUT based on AlScN could receive stable sound pressure signals under the bending radius of 1.5 cm. [ABSTRACT FROM AUTHOR]

This paper introduces a novel nondestructive wafer scale thin film thickness measurement method by detecting the reflected picosecond ultrasonic wave transmitting between different interfacial layers. Unlike other traditional approaches used for thickness inspection, this method is highly efficient in wafer scale, and even works for opaque material. As a demonstration, we took scandium doped aluminum nitride (AlScN) thin film and related piezoelectric stacking layers (e.g. Molybedenum/AlScN/Molybdenum) as the case study to explain the advantages of this approach. In our experiments, a laser with a wavelength of 515 nm was used to first measure the thickness of (1) a single Molybdenum (Mo) electrode layer in the range of 100–300 nm, and (2) a single AlScN piezoelectric layer in the range of 600–1000 nm. Then, (3) the combined stacking layers were measured. Finally, (4) the thickness of a standard piezoelectric composite structure (Mo/AlScN/Mo) was characterized based on the conclusions and derivation extracted from the aforementioned sets of experiments. This type of standard piezoelectric composite has been widely adopted in a variety of Micro-electromechanical systems (MEMS) devices such as the Piezoelectric Micromachined Ultrasonic Transducer (PMUT), the Film Bulk Acoustic Resonator (FBAR), the Surface Acoustic Wave (SAW) and more. A comparison between measurement data from both in-line and off-line (using Scanning Electron Microscope) methods was conducted. The result from such in situ 8-inch wafer scale measurements was in a good agreement with the SEM data. [ABSTRACT FROM AUTHOR]

There are great concerns for sensing using flexible acoustic wave sensors and lab-on-a-chip, as mechanical strains will dramatically change the sensing signals (e.g., frequency) when they are bent during measurements. These strain-induced signal changes cannot be easily separated from those of real sensing signals (e.g., humidity, ultraviolet, or gas/biological molecules). Herein, we proposed a new strategy to minimize/eliminate the effects of mechanical bending strains by optimizing off-axis angles between the direction of bending deformation and propagation of acoustic waves on curved surfaces of layered piezoelectric film/flexible glass structure. This strategy has theoretically been proved by optimization of bending designs of off-axis angles and acoustically elastic effect. Proof-of-concept for humidity and ultraviolet-light sensing using flexible SAW devices with negligible interferences are achieved within a wide range of bending strains. This work provides the best solution for achieving high-performance flexible acoustic wave sensors under deformed/bending conditions. [ABSTRACT FROM AUTHOR]

Half-wave plate (HWP) is one of the key polarization controlling devices in optical systems. The conventional HWPs based on birefringent crystals are inherently bulky and difficult to be monolithically integrated with other optical components. In this work, metasurface-based HWPs with high compactness are demonstrated on a 12-inch silicon complementary metal-oxide-semiconductor platform. Three-dimensional finite difference time domain simulation is used to design the nanostructure and investigate the impact of fabrication process variation on the device performance. In addition, the cross- and co-polarization transmittance (Tcross and Tco) of the HWPs located at different wafer locations are characterized experimentally. The peak Tcross and valley Tco values of 0.69 ± 0.053 and 0.032 ± 0.005 are realized at the wavelength around 1.7 μm, respectively. This corresponds to a polarization conversion efficiency of 95.6% ± 0.8%. [ABSTRACT FROM AUTHOR]

Metasurface-based beam deflector, as an important optical element to bend the light propagation direction, has drawn a lot of interests in research to achieve miniaturization of devices and reduction of system complexity. Based on the 12-inch immersion lithography technology, in this work, an ultra-thin and large-area pixelated metasurface beam deflector with a footprint of 2500 × 2500 μm, formed by nanopillars with diameters from 221 to 396 nm, is demonstrated on a 12-inch glass wafer. The 21 × 21 array of deflectors is designed to bend the input light in different directions and to generate 441 random points. In addition, the layer transfer on the 12-inch glass wafer makes the device working in transmission mode at a 940-nm wavelength. The random point array generated from the experiment shows good match with the design. This pixelated metasurface beam deflector can generate random points simultaneously and has potential to make beam steering by switching each pixel of the beam deflector, which can be applied on motion detection, facial recognition, and light detection and ranging. [ABSTRACT FROM AUTHOR]

In this paper, we present an experimental investigation of a water pipeline leak detection system based on a low-cost, tiny-sized hydrophone sensor fabricated using the microelectromechanical system (MEMS) technologies. A 10 × 10 element arrayed MEMS hydrophone device with chip size of 3.5 × 3.5 mm $^2$ was used in the experiment. The hydrophone device is packaged with a customized on-board preamplification circuit using an acoustic transparent material. The overall package size of the MEMS hydrophone is $\Phi$ 1.2 × 2.5 cm. The packaged MEMS hydrophone achieves an acoustic sensitivity of −180 dB (re: 1 V/ $\mu$ Pa), a bandwidth from 10 Hz to 8 kHz, and a noise resolution of around 60 dB (re: 1 $\mu \text{Pa/}\sqrt{\text{Hz}}$) at 1 kHz. A section of ductile iron water pipeline with an internal diameter of 10 cm, wall thickness of 0.73 cm, and length of 30 m is constructed as the test bed for the water leak detection. Two different leak sizes with leak flow rates of about 30 and 180 L/min are designed along the pipe, which is pressurized at 3.2 bar. Analysis of the transient signals and spectrograms shows that the MEMS hydrophone can capture the key acoustic information of the water leak, i.e., identifying the leak and locating the leak position. The measurement results demonstrate the feasibility to construct an affordable, highly efficient, real-time, and permanent in-pipe pipeline health monitoring network based on the MEMS hydrophones due to their high performance, low cost, and tiny size. [ABSTRACT FROM AUTHOR]

This paper studies the impact of two decision makers' interaction with conflicts on the efficiencies of the system. We start with a general principal-agent framework where the principal and the agent make decisions independently and the principal has a contradictive objective to that of the agent. We develop data envelopment analysis (DEA) models in the principal's and the agent's perspectives respectively. Non-cooperation between the principal and the agent is discussed to illustrate how one decision maker affects the other and the corresponding efficiency and incentive contract of the system. In addition, cooperation of the two parties is also analyzed to better derive how the performance of the system is influenced by the parties and their interactions as well. Then, this study illustrates the proposed models and effective incentive contracts by applying them to the efficiency evaluations of 22 China listed electric power companies. [ABSTRACT FROM AUTHOR]

In this letter, a group of laterally coupled alternating thickness (LCAT) mode resonators based on 12% scandium-doped aluminum nitride (Sc0.12Al0.88N) are reported. The LCAT mode resonators are realized in-house by sandwiching a layer of 1- $ {\mu }\text{m}$ -thick Sc0.12Al0.88N between the top two sets and the bottom two sets of interdigitated electrode (IDE) fingers, all made of molybdenum (Mo). The experimental results show that an effective electromechanical coupling coefficient ($ {k}_{{\text {eff}}}^{{2}}$) of more than 10% and loaded quality factors ($ {Q}_{ {L}}$) as high as 870 are obtained, while the motional resistance of the resonators is kept as low as 0.68 $ {\Omega }$. The figure-of-merit (FoM) which is defined as $ {k}_{{\text {eff}}}^{{2}}~{Q}_{L}$ and phase velocity ($ {v}_{ {p}}$) is subsequently derived to be 87 and 7840 m/s, respectively. By changing the pitch of the IDE fingers, the resonators can operate from 1.96 GHz to 2.11 GHz without significant perturbation to their performance, corresponding to a lithographic frequency tuning range of 7.5%. In addition, clean spectra without any spurious modes are obtained within a 1-GHz frequency range for all fabricated devices of various pitches, making a significant step forward in the commercialization path of the reported resonators in the applications of the high-band selection filters integrated on a single chip for mobile communication. [ABSTRACT FROM AUTHOR]

This paper presents the development of an 8-in six-degree-of-freedom (DOF) inertial sensor based on an advanced capacitive inertial sensor fabrication platform. The platform integrates three-axis gyroscopes and three-axis accelerometers on the same chip. The fabricated sensors are vacuum packaged at the wafer level with a polysilicon-based through-silicon interposer (TSI) using the aluminum–germanium eutectic bonding approach. Wafer-level measurement results indicate that a fabrication yield of greater than 92% and a vacuum level of $\sim$ 100 mtorr have been achieved. The fabricated inertial sensors and the customized application-specific integrated circuits are encapsulated in a 5 mm $\times$ 5 mm $\times$ 1.3 mm quad-flat no-leads package using the plastic molding technology. The system-level characterization of the developed six-DOF inertial sensors have been implemented. Several reliability tests conducted according to the relevant JEDEC standards prove that the packaged sensors are highly reliable and robust for a wide range of operating environments. [ABSTRACT FROM AUTHOR]

A high quality factor ($Q$) and low-impedance aluminum nitride (AIN) on silicon piezoelectric resonator is reported in this paper. The piezoelectric resonator is fabricated based on the AIN-on-cavity-Silicon-on-Insulator (SOI) platform and vacuum encapsulated using the wafer-level chip-scale packaging by aluminum–germanium eutectic bonding approach. The fabricated resonator achieves a loaded Q$ of 9520 and a motional impedance of 32.64 \Omega$ at its series resonant frequency of 27.19 MHz. Thermal cycles (TC) and highly-accelerated stress test (HAST) are performed to evaluated the packaging reliability of the fabricated devices. No obvious impedance change caused by the TC and HAST is observed. The TC results indicate that the packaged devices have an equivalent life of more than 11.65 years based on the Coffin–Manson model. The piezoelectric resonator-based programmable oscillators demonstrate an overall frequency drift of \pm$ 3 ppm over the temperature range of -C to 70  ^{\circ }C thanks to the passive and active temperature compensations. With this stable frequency reference, the programmable oscillator produces a 75.01-MHz frequency output. The measured integrated phase jitter is 2.02 ps (rms) from 12 to 10 MHz. [ABSTRACT FROM AUTHOR]

This letter reports the first implementation of a new class of laterally coupled alternating thickness (LCAT) mode resonators operating above 2 GHz, realised by replacing the bottom interdigitated electrodes of the conventional LCAT mode resonator with an electrically floating plate. Besides saving one mask process and relaxing the tight resolution and alignment requirements for defining small features, the flat unpatterned bottom electrode metal is also more favorable for the growth of highly oriented piezoelectric thin film, which results in an improved resonator quality factor ( $Q$ ). A group of 8% scandium doped aluminium nitride-based modified LCAT mode resonators with frequency difference over 100 MHz by varying the top interdigitated electrode pitches are fabricated achieving coupling coefficient ( {k}_{\textit {eff}}^{\textit {2}}) of up to 6.45% and figure of merit of up to 54, making them promising candidates for integrated band selection filter banks. [ABSTRACT FROM AUTHOR]

This letter reports on a nano-electro-mechanical system (NEMS) pressure sensor with p-doped silicon nanowires (average cross-sectional area ~100 nm2) as piezoresistive sensing elements. Taking advantage of surface micromachining, an absolute pressure-sensing device is developed using front-side isotropic etching. In contrast to the previously reported silicon nanowire (SiNW) pressure sensor processed with bulk micromachining through the backside deep reactive ion etching (DRIE), nonlinearity has been reduced to 0.31% (BFSL). In addition, the performance variations across the wafer have been significantly reduced to 6% in comparison with a 33% sensitivity fluctuation across the 8-inch wafer reported in our early work fabricated by a DRIE process. After front-side vacuum sealing, temperature-induced performance degradation has also been minimized. Moreover, the dramatic geometry downsizing (device footprint \sim 385~\mu \textm^\mathrm \mathbf 2 ) validates the scalability of the SiNW-based NEMS sensor. With excellent uniformity, the SiNW-based sensor can be commercially manufactured on an 8-inch wafer at lower cost with high yield. [ABSTRACT FROM AUTHOR]

In this paper, we have demonstrated an efficient perovskite light-emitting device (PeLED) by improving perovskite crystallization. The improved perovskite crystallization has been achieved by pretreating the underneath poly (3, 4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT: PSS) layer with N, N-dimethylformamide (DMF) solvent before single-step spin-coating the perovskite, which results in a prolonged wet environment during the perovskite thermal annealing process to promote the grain growth. The improved perovskite crystallization induces a perovskite thin film with higher surface coverage, fewer defects, and larger grain size with less scattering of grain boundaries. As a result, the PeLEDs exhibit maximum external quantum efficiency of 0.728% and maximum luminance of 2088 cd/m2, which represent a significant improvement over the control devices. Moreover, perovskite films with improved crystalline quality have proved its beneficial effect on the device stability. [ABSTRACT FROM PUBLISHER]

We report the intergrowth of ZIF-8 crystals on ultrathin graphene oxide (GO) membranes, which helps to reduce the non-selective pores of pristine GO membranes leading to gas selectivities as high as 406, 155, and 335 for H2/CO2, H2/N2, and H2/CH4 mixtures, respectively. [ABSTRACT FROM AUTHOR]

This letter reports an aluminium nitride (AlN)-based micromechanical resonator with high-effective coupling coefficient ( k\textrm {eff}^{2}) and low insertion loss (IL), which are comparable with those of Film Bulk Acoustic Resonators (FBARs). The in-house-fabricated resonator comprises of lithographically patterned top and bottom molybdenum interdigitated electrode fingers and a layer of 1- \mu \textm -thick AlN sandwiched in between. Synergetic inter-mode coupling between the constituent thickness mode and the lateral mode can be realized within a wide frequency range, which can be treated as a subcategory of degenerated cross-sectional Lamé mode, enabling the capability of lithographic tuning of resonant frequency yet not compromising k\textrm {eff}^{2} . Measurement results show that the designed 2.3-GHz resonator achieves a k\textrm {eff}^{2} of 6.34% and an IL of 0.26 dB upon direct connection to a network with 50- $\Omega $ termination, making it a promising candidate for Wireless Local Area Network (WLAN) and high band Long Term Evolution (LTE) band selection filtering applications. [ABSTRACT FROM PUBLISHER]

In this paper, a novel ring-down suppression system based on transfer function is proposed for the first time to suppress the ring-down time and decrease the blind area of PMUTs (Piezoelectric Micromachined Ultrasonic Transducers). This suppression system includes a transfer function and a simple P (proportion) controller, which can reduce the ring-down time without degrading any performances of PMUTs. The transfer function serves as a virtual PMUT device, feeding its output into the P controller; then, the P controller generates a suppression signal to the actual PMUT device. The ring-down time of a 115-kHz PMUT array is demonstrated to be reduced by up to 93% through the suppression system. In addition, the P controller has been experimentally optimized, reducing the blind area of the PMUT array by about 40%. Moreover, a low ring-down PMUTs system design guideline is established, which is practical and straightforward for industrial scenarios. Finally, the system can be easily integrated into ASIC (Application Specific Integrated Circuit). [ABSTRACT FROM AUTHOR]

In this letter, we report a miniaturization strategy for harvesting a low-frequency random vibration energy with a piezoelectric energy harvesting (EH) system utilizing coupled Helmholtz resonance and vortex shedding effect. This is made possible by transferring the low-frequency vibration energy into a pressurized fluid, which is in turn converted into predefined, pressure-independent high-frequency energy harvested by the device. The vibration-pressurized fluid conversion extends the device sampling frequency band; enables efficient harvesting of broadband low vibration frequencies with small form factor. Proof of concept of the proposed strategy has been demonstrated with an AlN-based MEMS EH, which delivered an output power density of 95.5 mW/cm^3 under a constant input airflow at 4.2 lbf/in^2 pressure. [ABSTRACT FROM PUBLISHER]

Presents corrections to the above named paper. [ABSTRACT FROM AUTHOR]

In this paper we demonstrate a novel acoustic wave pressure sensor, based on an aluminum nitride (AlN) piezoelectric thin film. It contains an integrated vacuum cavity, which is micro-fabricated using a cavity silicon-on-insulator (SOI) wafer. This sensor can directly measure the absolute pressure without the help of an external package, and the vacuum cavity gives the sensor a very accurate reference pressure. Meanwhile, the presented pressure sensor is superior to previously reported acoustic wave pressure sensors in terms of the temperature drift. With the carefully designed dual temperature compensation structure, a very low temperature coefficient of frequency (TCF) is achieved. Experimental results show the sensor can measure the absolute pressure in the range of 0 to 0.4 MPa, while the temperature range is from 20 °C to 220 °C with a TCF of −14.4 ppm/°C. Such a TCF is only about half of that of previously reported works. [ABSTRACT FROM AUTHOR]

This paper presents three-dimensional (3D) models of high-frequency piezoelectric micromachined ultrasonic transducers (PMUTs) based on the finite element method (FEM). These models are verified with fabricated aluminum nitride (AlN)-based PMUT arrays. The 3D numerical model consists of a sandwiched piezoelectric structure, a silicon passive layer, and a silicon substrate with a cavity. Two types of parameters are simulated with periodic boundary conditions: (1) the resonant frequencies and mode shapes of PMUT, and (2) the electrical impedance and acoustic field of PMUT loaded with air and water. The resonant frequencies and mode shapes of an electrically connected PMUT array are obtained with a laser Doppler vibrometer (LDV). The first resonant frequency difference between 3D FEM simulation and the measurement for a 16-MHz PMUT is reasonably within 6%, which is just one-third of that between the analytical method and the measurement. The electrical impedance of the PMUT array measured in air and water is consistent with the simulation results. The 3D model is suitable for predicting electrical and acoustic performance and, thus, optimizing the structure of high-frequency PMUTs. It also has good potential to analyze the transmission and reception performances of a PMUT array for future compact ultrasonic systems. [ABSTRACT FROM AUTHOR]

Detection of volatile organic compounds (VOCs) at parts-per-billion (ppb) level is one of the most challenging tasks for miniature gas sensors because of the high requirement on sensitivity and the possible interference from moisture. Herein, for the first time, we present a novel platform based on a hybrid photonic cavity with metal-organic framework (MOF) coatings for VOCs detection. We have fabricated a compact gas sensor with detection limitation ranging from 29 to 99 ppb for various VOCs including styrene, toluene, benzene, propylene and methanol. Compared to the photonic cavity without coating, the MOF-coated solution exhibits a sensitivity enhancement factor up to 1000. The present results have demonstrated great potential of MOF-coated photonic resonators in miniaturized gas sensing applications. [ABSTRACT FROM AUTHOR]

In the above paper , there are two typos in the abstract and last page. The 95.5 mW/cm^3 should be 95.5 \muW/cm^3 . The calculation based on the power output and the volume of the device. The dimension of the device is shown in the following figure: [ABSTRACT FROM AUTHOR]