MEMS Biomimetic Acoustic Pressure Gradient Sensitive Structure for Sound Source Localization

The parasitoid fly Ormia ochracea shows an astonishing localization ability with its tiny hearing organ. A novel MEMS biomimetic acoustic pressure gradient sensitive structure was designed and fabricated by mimicking the mechanically coupled tympana of the fly. Firstly, the analytic representation formulas of the resultant force and resultant moment of the incoming plane wave acting on the structure were derived. After that, structure modal analysis was performed and the results show that the structure has out-of-phase and in-phase vibration modes, and the corresponding eigenfrequency is decided by the stiffness of vertical torsional beam and horizontal beam respectively. Acoustic-structural coupled analysis was performed and the results show that phase difference and amplitude difference between the responses of the two square diaphragms of the sensitive structure are effectively enlarged through mechanical coupling beam. The phase difference and amplitude difference increase with increasing incident angle and can be used to distinguish the direction of sound arrival. At last, the fabrication process and results of the device is also presented

Transitional pulsatile flows with stenosis in a two-dimensional channel

Although blood flows are mostly laminar, transition to turbulence and flow separations are observed at curved vessels, bifurcations, or constrictions. It is known that wall-shear stress plays an important role in the development of atherosclerosis as well as in arteriovenous grafts. In order to help understand the behavior of flow separation and transition to turbulence in post-stenotic blood flows, an experimental study of transitional pulsatile flow with stenosis was carried out using time-resolved particle image velocimetry and a microelectromechanical systems wall-shear stress sensor at the mean Reynolds number of 1750 with the Womersley number of 6.15. At the start of the pulsatile cycle, a strong shear layer develops from the tip of the stenosis, increasing the flow separation region. The flow at the throat of the stenosis is always laminar due to acceleration, which quickly becomes turbulent through a shear-layer instability under a strong adverse pressure gradient. At the same time, a recirculation region appears over the wall opposite to the stenosis, moving downstream in sync with the movement of the reattachment point. These flow behaviors observed in a two-dimensional channel flow are very similar to the results obtained previously in a pipe flow. We also found that the behavior in a pulsating channel flow during the acceleration phase of both 25% and 50% stenosis cases is similar to that of the steady flow, including the location and size of post-stenotic flow separation regions. This is because the peak Reynolds number of the pulsatile flow is similar to that of the steady flow that is investigated. The transition to turbulence is more dominant for the 50% stenosis as compared to the 25% stenosis, as the wavelet spectra show a greater broadening of turbulence energy. With an increase in stenosis to 75%, the accelerating flow is directed toward the opposite wall, creating a wall jet. The shear layer from the stenosis bifurcates as a result of this, one moving with the flow separation region toward the upper wall and the other with the wall jet toward the bottom wall. Low wall-shear stress fluctuations are found at two post-stenotic locations in the channel flow – one immediately downstream of the stenosis over the top wall (stenosis side) inside the flow separation region, and the other in the recirculation region on the bottom wall (opposite side of the stenosis)

Signal Processing of MEMS Gyroscope Arrays to Improve Accuracy Using a 1st Order Markov for Rate Signal Modeling

This paper presents a signal processing technique to improve angular rate accuracy of the gyroscope by combining the outputs of an array of MEMS gyroscope. A mathematical model for the accuracy improvement was described and a Kalman filter (KF) was designed to obtain optimal rate estimates. Especially, the rate signal was modeled by a first-order Markov process instead of a random walk to improve overall performance. The accuracy of the combined rate signal and affecting factors were analyzed using a steady-state covariance. A system comprising a six-gyroscope array was developed to test the presented KF. Experimental tests proved that the presented model was effective at improving the gyroscope accuracy. The experimental results indicated that six identical gyroscopes with an ARW noise of 6.2 °/√h and a bias drift of 54.14 °/h could be combined into a rate signal with an ARW noise of 1.8 °/√h and a bias drift of 16.3 °/h, while the estimated rate signal by the random walk model has an ARW noise of 2.4 °/√h and a bias drift of 20.6 °/h. It revealed that both models could improve the angular rate accuracy and have a similar performance in static condition. In dynamic condition, the test results showed that the first-order Markov process model could reduce the dynamic errors 20% more than the random walk model

Design and Simulation of a MEMS Control Moment Gyroscope for the Sub-Kilogram Spacecraft

A novel design of a microelectromechanical systems (MEMS) control moment gyroscope (MCMG) was proposed in this paper in order to generate a torque output with a magnitude of 10−6 N·m. The MCMG consists of two orthogonal angular vibration systems, i.e., the rotor and gimbal; the coupling between which is based on the Coriolis effect and will cause a torque output in the direction perpendicular to the two vibrations. The angular rotor vibration was excited by the in-plane electrostatic rotary comb actuators, while the angular gimbal vibration was driven by an out-of-plane electrostatic parallel plate actuator. A possible process flow to fabricate the structure was proposed and discussed step by step. Furthermore, an array configuration using four MCMGs as an effective element, in which the torque was generated with a phase difference of 90 degrees between every two MCMGs, was proposed to smooth the inherent fluctuation of the torque output for a vibrational MCMG. The parasitic torque was cancelled by two opposite MCMGs with a phase difference of 180 degrees. The designed MCMG was about 1.1 cm × 1.1 cm × 0.04 cm in size and 0.1 g in weight. The simulation results showed that the maximum torque output of a MCMG, the resonant frequency of which was approximately 1,000 Hz, was about 2.5 × 10−8 N·m. The element with four MCMGs could generate a torque of 5 × 10−8 N·m. The torque output could reach a magnitude of 10−6 N·m when the frequency was improved from 1,000 Hz to 10,000 Hz. Using arrays of 4 × 4 effective elements on a 1 kg spacecraft with a standard form factor of 10 cm × 10 cm × 10 cm, a 10 degrees attitude change could be achieved in 26.96 s

Functional roles of two novel P450 genes in the adaptability of Conogethes punctiferalis to three commonly used pesticides

Introduction: Insect cytochrome P450 (CYP450) genes play important roles in the detoxification and metabolism of xenobiotics, such as plant allelochemicals, mycotoxins and pesticides. The polyphagous Conogethes punctiferalis is a serious economic pest of fruit trees and agricultural crops, and it shows high adaptability to different living environments.Methods: The two novel P450 genes CYP6CV1 and CYP6AB51 were identified and characterized. Quantitative real-time PCR (qRT-PCR) technology was used to study the expression patterns of the two target genes in different larval developmental stages and tissues of C. punctiferalis. Furthermore, RNA interference (RNAi) technology was used to study the potential functions of the two P450 genes by treating RNAi-silenced larvae with three commonly used pesticides.Results: The CYP6CV1 and CYP6AB51 genes were expressed throughout various C. punctiferalis larval stages and in different tissues. Their expression levels increased along with larval development, and expression levels of the two target genes in the midgut were significantly higher than in other tissues. The toxicity bioassay results showed that the LC50 values of chlorantraniliprole, emamectin benzoate and lambda-cyhalothrin on C. punctiferalis larvae were 0.2028 μg/g, 0.0683 μg/g and 0.6110 mg/L, respectively. After treating with different concentrations of chlorantraniliprole, emamectin benzoate and lambda-cyhalothrin (LC10, LC30, LC50), independently, the relative expressions of the two genes CYP6CV1 and CYP6AB51 were significantly induced. After the dsRNA injection, the expression profiles of the two CYP genes were reduced 72.91% and 70.94%, respectively, and the mortality rates of the larvae significantly increased when treated with the three insecticides independently at LC10 values.Discussion: In the summary, after interfering with the CYP6CV1 and CYP6AB51 in C. punctiferalis, respectively, the sensitivity of C. punctiferalis to chlorantraniliprole, emamectin benzoate and lambda-cyhalothrin was significantly increased, indicating that the two CYP6 genes were responsible for the adaptability of C. punctiferalis to the three chemical insecticides in C. punctiferalis. The results from this study demonstrated that CYP6CV1 and CYP6AB51 in C. punctiferalis play crucial roles in the detoxification of chlorantraniliprole, emamectin benzoate and lambda-cyhalothrin

Ultra-Sensitive, Deformable and Transparent Triboelectric Tactile Sensor based on Micro-Pyramid Patterned Ionic Hydrogel for Interactive Human-Machine Interfaces

Rapid advances in wearable electronics and mechno-sensational human-machine interfaces impose great challenges in developing flexible and deformable tactile sensors with high efficiency, ultra-sensitivity, environment-tolerance and self-sustainability. Herein, we report a tactile hydrogel sensor (THS) based on micro-pyramid-patterned double-network (DN) ionic organohydrogels to detect subtle pressure changes by measuring the variations of triboelectric output signal without an external power supply. By the first time of pyramidal-patterned hydrogel fabrication method and laminated PDMS encapsulation process, the self-powered THS shows the advantages of remarkable flexibility, good transparency (~85), and excellent sensing performance, including extraordinary sensitivity (45.97 mV Pa-1 ), fast response (~20 ms), very low limit of detection (50 Pa) as well as high stability (36000 cycles). Moreover, with the LiBr immersion treatment method, the THS possesses excellent long-term hyper antifreezing and anti-dehydrating properties, broad environment tolerance (-20 to 60 ℃), and instantaneous peak power density of 20 μW cm-2 , providing reliable contact outputs with different materials and detecting very slight human motions. The THS shows no apparent output decline under the extreme environments of −29℃, 60℃ and even the vacuum conditions, demonstrating the excellent application potential in the field of harsh environments. By integrating the signal acquisition/process circuit, the THS with excellent self-power sensing ability is utilized as a switching button to control electric appliances and robotic hands by simulating human finger gestures, offering its great potentials for wearable and multi-functional electronic applications

Hierarchical Honeycomb-structured Electret/Triboelectric Nanogenerator for Biomechanical and Morphing Wing Energy Harvesting

Flexible, compact, lightweight and sustainable power sources are indispensable for modern wearable and personal electronics and small-unmanned aerial vehicles (UAVs). Hierarchical honeycomb has the unique merits of compact mesostructures, excellent energy absorption properties and considerable weight to strength ratios. Herein, a honeycomb-inspired triboelectric nanogenerator (h-TENG) is proposed for biomechanical and UAV morphing wing energy harvesting based on contact triboelectrification wavy surface of cellular honeycomb structure. The wavy surface comprises a multilayered thin film structure (combining polyethylene terephthalate, silver nanowires and fluorinated ethylene propylene) fabricated through high-temperature thermoplastic molding and wafer-level bonding process. With superior synchronization of large amounts of energy generation units with honeycomb cells, the manufactured h-TENG prototype produces the maximum instantaneous open-circuit voltage, short-circuit current and output power of 1207 V, 68.5 μA and 12.4 mW, respectively, corresponding to a remarkable peak power density of 0.275 mW/cm3 (or 2.48 mW/g) under hand-pressing excitations. Attributed to the excellent elastic property of self-rebounding honeycomb structure, the flexible and transparent h-TENG can be easily pressed, bent, and integrated into shoes for real-time insole plantar pressure mapping. The lightweight and compact h-TENG is further installed into a morphing wing of small UAVs for efficiently converting the flapping energy of ailerons into electricity for the first time. This research demonstrates this new conceptualizing single h-TENG device's versatility and viability for broad-range real-world application scenarios

Oxidative dehydrogenation of ethane to ethylene over LiCl/SO42--ZrO2 catalyst

Sulfated zirconia (SO42--ZrO2) samples were prepared by a modified two-step method (refluxing ZrO(OH)(2) precursor in basic solution followed by drying and (NH4)(2)SO4 impregnation) and then impregnated with a LiCl solution to give the SO42--ZrO2-supported LICI catalysts with Li mass content of 0.5% similar to 15%. The catalysts were characterized by X-ray diffraction, scanning electron microscopy, N-2 adsorption, temperature-programmed desorption-mass spectrometry, and X-ray photoelectron spectroscopy. The results show that with increasing LiCl loading, the specific surface area and acidity of the catalysts as well as the volume fraction of tetragonal zirconia in the catalysts decrease, while the catalytic performance of the catalysts for oxidative dehydrogenation of ethane (ODHE) to ethylene increases. Over the LiCl/SO42--ZrO2 catalyst with a Li content of 15% ethylene yield of 77.8% with an ethane conversion of 90.6% is achieved at 650 degrees C, and the yield higher than 71% is maintained over a period of 24 h. The textural structure of ZrO? has little effect on the catalytic behavior of the LiCl/SO42--ZrO2 catalysts. The specific surface area of SO42--ZrO2 samples prepared by the fled two-step method is much bigger than that of the SO42--ZrO2 samples made by the method reported in literature, and therefore more LiCl call be loaded on unit mass of support. This is favorable to improve the catalyst stability and slow down catalyst deactivation during the ODHE reaction due to the loss of LiCl

The carrier-generating analysis of MEMS gyroscope interface circuit

In this paper, the main factors which influence the noise ratio of gyroscope output signal were analysed, according to the MEMS gyro interface circuit technology. A working principle of a carrier in the gyroscope circuit was discussed, the process formula of the carrier amplitude and frequency in the interface circuit of modulation and demodulation was deduced, and the error components lead-in from carrier to gyroscope circuit was distinguished. Several commonly used carrier-generating circuit schemes were analysed and compared, and a carrier-generating program in the interface circuits of the micro-gyroscope was designed, which was applied in a MEMS gyro developed by our laboratory. The measurement results show that the amplitude stability and frequency stability is 1.3 ppm and 12 ppm, respectively, meeting the performance requirements of carrier generating in the MEMS gyro circuit