查看更多>>摘要：Ultrasonic transducers are widely employed in many fields such as non-destructive testing (NDT), petrochemical refineries, aerospace field, etc., in which high temperature ultrasonic transducers are necessary because many measurements must be done at elevated temperature. In this work, 4.5 MHz high temperature ultrasonic transducers with delay line were designed and fabricated based on BiScO3-Pb(Ti0.99Zn0.01)O-3 (BS-0.01PZnT) piezoelectric ceramics possessing excellent temperature stability and high Curie temperature. The experimental results revealed that-6 dB bandwidth and the center frequency of high temperature ultrasonic transducers are around 129% and 4.5 MHz, respectively, which are almost stable from room temperature to 400 degrees C. The peak-to peak values (V-pp) is as large as 1.5 V at RT, indicating very high sensitivity. More importantly, the ultrasonic transducers with customized BS-0.01PZnT ceramics can work reliably at high temperature of 380 degrees C and 450 degrees C by in-situ measurement at elevated temperatures. This work verifies the great potential application values of ultrasonic transducers with BS-0.01PZnT ceramics in high temperature applications.
查看更多>>摘要：The effect of a coating on the sensitivity of polyvinylidene fluoride (PVDF) is investigated in this study and the underlying physical mechanisms are explained. The spectral and directional sensitivity of a coated PVDF film are significantly different from that of an uncoated PVDF film, and this can be explained by the amplification of the in-plane stress component by the transmitted shear stress at the PVDF-coating interface. The amplification is dependent on the elastic property and thickness of the coating material. The sensitivity of the coated PVDF film below the first resonance frequency, owing to the destructive superposition of in-plane and normal voltage components, can be increased by adding a thick and soft coating or a thin and stiff coating. A thick and soft coating significantly amplifies the in-plane voltage component and makes it dominant, while a thin and stiff coating reduces the in-plane voltage component and hence the normal voltage component becomes dominant. The directivity sensitivity of the film at low frequency is also explained by the angular dependence of the PVDF-coating interaction. The demonstrated effect of the coating material on the spectral and directional sensitivity of PVDF helps in understanding the measured results of existing PVDF hydrophones, and in designing PVDF-based hydrophones and acoustical intensity probes with a desired response.
查看更多>>摘要：Various microelectromechanical (MEM) resonator topologies have been proposed for liquid phase sensing applications. Low liquid phase motional resistance (Rm) and moderately high liquid phase quality factor (Q) are critical to the performance of oscillators based on these resonators for real-time frequency tracking in sensing applications. We recently described a new topology we call the elliptical plate resonator EPR that delivers the lowest Rm after normalizing for area (which impacts mass sensitivity as a tradeoff for lower Rm). In this work, we show that further significant gains in performance can be made by choice of device alignment to the silicon crystal axis (< 110 > direction vs. < 100 > direction). We compare the liquid phase performance between the two orientations for a range of geometrical ratios defining the ellipse of the device. We show that the orientation makes a notable difference on trends in liquid phase Q and Rm. By aligning the EPR to the < 110 > direction, we demonstrate a liquid phase Q of 310 and Rm of 2.5 k ohm. Normalizing for area (RmxA) to express the tradeoff between mass sensitivity and electrical performance in relation to device area, we report an RmxA of 0.25 k ohm. mm2. We also show that these gains in liquid phase Rm and Q translate into significant lowering of the Allan deviation when these devices are embedded in close loop to track their frequency in real time with water loaded on the device as expected in liquid phase sensing applications.
查看更多>>摘要：2-2 mode piezocomposites are widely used for the drive section of acoustic transducers. Typically, piezocomposites have been developed using theoretical or numerical methods such as the finite element method. However, rigorous analysis of piezocomposites has always been difficult due to their complicated two-phase structure, which necessitates homogenization of the structure with a single-phase material with properties identical to those of the original two-phase piezocomposite. In this study, we determined the material properties of the equivalent single-phase material using the resonator method. The asymptotic averaging method was used to obtain the initial properties of the homogenized material, which had some accuracy limitations. We improved the accuracy by using multiple resonators, each of which reflected the effect of different material constants. We adjusted the material constants that influence each resonator to minimize the difference between the original piezocomposite's resonant and antiresonant frequencies and those of the equivalent single-phase material. The optimization technique was used to facilitate this adjustment. The homogenized material with the optimized material constants represented the original two-phase piezocomposite very well. The new method proposed in this study to homogenize the 2-2 mode piezocomposites can be applied to the accurate design of various piezocomposite transducers.
Darwish, A. A. A.Qashou, Saleem, IAlenezy, A. G. K.Al Garni, S. E....
8页
查看更多>>摘要：In this paper, Erbium(III)-Tris(8-hydroxyquinolinato) (Erq3), with the empirical formula: C27H18ErN3O3, has been introduced as a photoelectronic performance sensor of a promised candidate film with high sensitivity to NO2 gas. The present film was prepared by the thermal vacuum process, and the structure and composition of Erq3were investigated by the analysis of XRD-pattern, FTIR-spectra, and AFM technique. A polycrystalline with a single peak (at the centered Bragg's angle, 2 theta = 11.40 degrees) has been observed for the Erq3 film. AFM images indicate that the film surface is composed of distributed plateaus. The absorption spectrum showed three absorption bands at 265 nm corresponding to f-pi* transitions, while the peaks at 330 and 375 nm are attributed to the pi-pi* transitions. The band gap energy was evaluated by Tauc relation, while the electronic transition was indirect. The response time, recovery time, and sensitivity at the operating temperature of 348 K were 1.46 s, 14.2 s, and 20%, respectively. A comparison of sensor parameters with other relative materials was also reported.
查看更多>>摘要：Procalcitonin (PCT) is an important biomarker of bacterial infections. Detection of serum PCT is of great significance in diagnosis and therapy of a variety of diseases. In this work it is measured through immunoassay using antibody-conjugated fluorescent microspheres. To improve the binding efficiency of PCT antigen and antibody, an aeroelastic agitator is designed. Through alternate perturbations, it produces chaotic advection to enhance the fluid mixing. The influences of key design and operating factors are analyzed, including the geometrical parameters, the driving pressure, and the alternating period. Then the agitator is applied for PCT detection and its performance is compared with an ultrasonic mixer. Results show that the chaotic mixing significantly improves the capturing efficiency of PCT antigen, leading to a better detection consistency and reliability. The fluorescence intensity correlates fairly well with the serum PCT concentration in the range of 0.02 ng/ml-49.56 ng/ml.
查看更多>>摘要：Advances in the integration of wearable devices in our daily life have led to the development of new electrode designs for biopotential monitoring. Historically, the development and testing of wearable electrodes for the acquisition of biopotential signals has been empirical, relying on experiments on human volunteers. However, the lack of explicit control on human variables, the intra-, and inter-subject variability complicates the understanding of the performance of these wearable electrodes. Herein, phantom mimicking the electrical properties of the skin in the low-frequency range (1-1000 Hz), which has the potential to be used as a platform for controlled benchtop experiments for testing electrode functionality, is demonstrated. The fabricated phantom comprises two layers representing the deeper tissues and stratum corneum. The lower layer of the phantom mimicking deeper tissues was realized using polyvinyl alcohol cryogel (PVA-c) prepared with 0.9% W/W saline solution by a freeze-thaw technique. The properties of the upper layer representing the stratum corneum were simulated using a 100 mu m thick layer fabricated by spin-coating a mixture of polydimethylsiloxane (PDMS), 2.5% W/W carbon black (CB) for conductance, and 40% W/W barium titanate (BaTiO3) as a dielectric. The hydration of the stratum corneum was modeled in a controlled way by varying porosity of the phantom's upper layer. Impedance spectroscopy measurements were carried out to investigate the electrical performance of the fabricated phantom and validated against the impedance response obtained across a physiological skin impedance range of five human subjects. The results indicated that the Bode plot depicting the impedance response obtained on the phantom was found to lie in the human skin range. Moreover, it was observed that the change of porosity provides control over the hydration and the phantom can be tuned as per the skin ranges among different individuals. Also, the phantom was able to mimic the impact of dry and hydrated skin on a simulated ECG signal in the time domain. The developed skin phantom is affordable, fairly easy to manufacture, stable over time, and can be used as a platform for benchtop testing of new electrode designs.
Rizal, MuhammadHusniMubarak, Amir ZakiDirhamsyah, Muhammad...
11页
查看更多>>摘要：A piezoelectric energy harvester based on rotational motion is a promising technique to generate unlimited electrical energy. However, the necessity for an effective harvester that can be mounted on a rotating system has become an important issue as a support for self-powered wireless sensor systems. The purpose of this study is to develop a novel magnetically impelled piezoelectric rotating energy harvester integrated into a rotating spindle, which is excited by multiple magnetic pairs between symmetrically opposed stationary and spinning magnets on the surface of piezoelectric discs. The theoretical examination of the magnetic excitation on a harvester system is provided to determine magnetic the force and torque, while the voltage and power generation capability of a magnetically impelled piezoelectric rotational energy harvester under various series and parallel configurations, and spindle speed excitations were examined experimentally. The experimental results are in line with the analytical model of magnetic force, which showed that the resistance torque can be decreased significantly. A maximum instantaneous output voltage of -15-19 V and 7.5-8 V was achieved at series and parallel connection respectively. The maximum power can be obtained at parallel connection and the RMS and peak power are 870 mu W and 3500 mu W, respectively and a high power density of 9.67 mu W/mm3. The harvester can also charge the capacitors with voltage and power saturation of 6 V and 327 mu W respectively. These results showed that the suggested harvester has high durability and the potential to power wireless sensors that are integrated into spindle machines.
查看更多>>摘要：Using a pre-designed, simple, and cost-effective acoustic hologram alongside a single ultrasonic transducer, as an acoustic source/transmitter, enables new capabilities in multi-focal focusing, acoustic patterning, and contactless ultrasonic power transfer (UPT), to selectively charge sensors/receivers. In this work, different multi-focal holograms are designed that cover single-to four-focus acoustic patterning for UPT purposes. The holograms are numerically designed to create multi-focal pressure patterns in a target plane where an array of receivers are placed. The incident sound wave from a transmitter, after passing through the hologram, is manipulated, hence, the output field is the desired pressure field, which excites the receivers located at the pre-determined focal points more significantly. Proof-of-concept experiments are also performed for a five-element receiver setup, using a two-focus hologram, to selectively power two specific receivers. The experiments indicate a significant electrical average power output enhancement ratio of 23.4 from the targeted receivers, compared to untargeted ones, which proves the functionality of the designed multi-focal holograms in arbitrarily patterning the con tactless transfer of ultrasonic power.
查看更多>>摘要：Aligning two mold inserts is one of the most important steps in the punching of through-holes for polymer microfluidic devices. Significant misalignment of the mold inserts could reduce device functionality or allow for interference between mold inserts. Active and iterative methods require repetitive experiments, characterization, and mold adjustments making the process tedious. Passive set-up alignment using a temporary kinematic coupling can be an alternative to the active and iterative methods. To do this, the three v-grooves on the primary mold insert mate with the three spheres set in dimples on the complementary mold insert. Once the mold inserts are aligned and secured, the spheres are removed, and face-to-face contact between the mold inserts can be achieved for the molding operation. This aligns the primary and complementary mold inserts without any repeated measurements or adjustments. To validate the proposed design, primary and complementary mold inserts were fabricated with alignment joints and features to conduct a punching process. Prior to assembling the mold inserts to the thermal press for punching, they were pre-assembled to inspect the innate misalignment due to the machining of the mold inserts. Along the X-Axis, the X-magnitude (delta X-i) of the mean misalignment ranged from 2 to 7 mu m and the Y-magnitude (delta Y-i,) of the mean misalignment were from 7 to 13 mu m. The X-and Y magnitude (delta X-j and delta Y-j) of mean misalignment along the Y-Axis ranged from 1 to 4 mu m, and 5-12 mu m, respectively. The mold inserts were aligned and subsequently mounted to the thermal press. Punching was conducted on a polymer substrate Misalignment was the displacement of the center-point of a die hole impression from the center point of a through-hole. The X-and Y-magnitudes of the mean misalignment (delta X-k and delta Y-k) along the X-Axis ranged from 12 to 82 mu m and 32-72 mu m, respectively. The X-and Y-magnitudes of the misalignment (delta X-l and delta Y-l) along Y-Axis were 11-71 mu m and 32-70 mu m, respectively. The results of experiments showed that the proposed passive alignment method is applicable to the punching of through-holes for polymer microfluidic devices.
NSTL
Elsevier