Micromachines最新文献

This paper highlights the optimisation of a key design parameter essential to the development of PMUTs, which are part of the transmitting components of microsensors. These microsensors are designed for use in the Structural Health Monitoring of reinforced concrete structures. Enhancing the effectiveness of the transmitting component allows for greater spacing between microsensors, which in turn reduces the number of devices needed to implement a full structural health monitoring system. PMUTs designed for integration into the pore solution of reinforced concrete structures need to operate effectively with liquid coupling fluids to ensure optimal sonic energy transfer into the structure. This paper outlines the techniques employed to optimize the central electrode's percentage radial cover of the piezoelectric layer, in circular PMUTs resonating at around 100 kHz. This optimisation was achieved using Finite Element Modelling, laser vibrometry, and hydrophone experimental techniques. The results demonstrated that a radial electrode cover between 65 and 70% significantly enhances the kinematic and dynamic characteristics of a PMUT's diaphragm when subjected to the excitation of a sine wave electrical signal. The paper also includes advanced time domain finite element analysis, through which the authors aimed to illustrate the diaphragm's movements at various levels of radial electrode coverage.

This paper presents a W-band power amplifier monolithic microwave integrated circuit (MMIC) that is designed for high-precision millimeter-wave systems and fabricated using a 0.1 µm GaAs pHEMT process. The amplifier's stability was evaluated using the network determinant function, ensuring robust performance under both linear and nonlinear conditions. Simultaneous matching for gain and output power was achieved with minimal passive elements. The developed power amplifier MMIC exhibits a linear gain exceeding 20 dB and an input return loss greater than 6 dB across the 88-98 GHz range. It delivers an output power of 23.8-24.1 dBm with a power gain of 17.3-17.9 dB in the 88-97 GHz range and achieves a maximum power-added efficiency (PAE) of 24% at 94 GHz.

In recent years, microfluidics has emerged as an interdisciplinary field, receiving significant attention across various biomedical applications. Achieving a noticeable mixing of biofluids and biochemicals at laminar flow conditions is essential in numerous microfluidics systems. In this research work, a new kind of micromixer design integrated with an Archimedes screw is designed and investigated using numerical simulation and experimental approaches. First, the geometrical parameters such as screw length (l), screw pitch (p) and gap (s) are optimized using the Design of Expert (DoE) approach and the Central Composite Design (CCD) method. The experimental designs generated by DoE are then numerically simulated aiming to determine Mixing Index (MI) and Performance Index (PI). For this purpose, COMSOL Multiphysics with two physics modules-laminar and transport diluted species-is used. The results revealed a significant influence of screw length, screw pitch and gap on mixing performance. The optimal design achieved is then scaled up and fabricated using a 3D additive manufacturing technique. In addition, the optimal micromixer design is numerically and experimentally investigated at diverse Reynolds numbers, ranging from 2 to 16. The findings revealed the optimal geometrical parameters that produce the best result compared to other designs are a screw length of 0.5 mm, screw pitch of 0.23409 mm and a 0.004 mm gap. The obtained values of the mixing index and the performance index are 98.47% and 20.15 Pa^-1, respectively. In addition, a higher mixing performance is achieved at the lower Reynolds number of 2, while a lower mixing performance is observed at the higher Reynolds number of 16. This study can be very beneficial for understanding the impact of geometrical parameters and their interaction with mixing performance.

In recent years, liquid-solid triboelectric nanogenerators (L-S TENGs) have been rapidly developed in the field of liquid energy harvesting and self-powered sensing. This is due to a number of advantages inherent in the technology, including the low cost of fabricated materials, structural diversity, high charge-energy conversion efficiency, environmental friendliness, and a wide range of applications. As liquid phase dielectric materials typically used in L-S TENG, a variety of organic and inorganic single-phase liquids, including distilled water, acidic solutions, sodium chloride solutions, acetone, dimethyl sulfoxide, and acetonitrile, as well as paraffinic oils, have been used in experiments. However, it is noteworthy that the function of multiphase liquids as dielectric materials is still understudied. The "Multiphase Liquid Triboelectric Nanogenerator Prototype (ML-TENG Pro)" presented in this paper takes a single-electrode solid-liquid triboelectric nanogenerator as the basic model and uses lubricating oil and deionized water as dielectric materials. After verifying the stability of single-phase liquid materials (e.g., DI water, seawater, ethanol, etc.) for power generation, the power generation performances of oil-water two-phase, gas-oil-water three-phase (with a small number of bubbles), and gas-oil-water three-phase (with many bubbles) in open space are further investigated. COMSOL Multiphysics 6.0 software was used to investigate the material transport mechanism and formation of oil-water two-phase and gas-oil-water three-phase. Finally, this study presents the power generation performance of ML-TENG Pro in the extreme state of gas-oil-water three-phase "emulsification". This paper outlines the limitations of the ML-TENG, named PRO, and suggests avenues for future improvement. The research presented in this paper provides a theoretical basis for evaluating the quality of lubricants for mechanical power equipment.

Photonic and optoelectronic devices and systems are at the forefront of modern technology, enabling the precise manipulation of light for a wide range of applications [...].

Microfluidics and biochip technologies continue to play a key role in driving innovation across biomedical, environmental and engineering disciplines [...].

On-chip gene synthesis has the potential to improve the synthesis throughput and reduce the cost exponentially. While there exist several microarray-based oligo synthesis technologies, on-chip gene assembly has yet to be demonstrated. This work introduces a novel on-chip DNA assembly method via dielectrophoresis (DEP) that can potentially be integrated with microarray-based oligo synthesis on the same chip. Our DEP chip can selectively manipulate oligos and guide their movement without perturbing the surrounding fluid medium, thus aiding in DNA assembly. Helical forked electrode design has been optimized for compatibility with DEP, ensuring efficient control over target oligos. By applying an alternating current signal set at 2 MHz, we successfully achieve the desired directed movement of oligonucleotides. Additionally, chemical treatments combined with photoirradiation enabled the connection of complementary gene sequences and the subsequent release of single-stranded DNA products. Sequencing results validate the effective assembly of DNA fragments, approximately 500 base pairs in length, using our DEP device.

This study evaluates the performance of continuous flow and drop-based microfluidic devices for the synthesis of silver nanoparticles (AgNPs) under identical hydrodynamic and chemical conditions. Flows at low values of Dean number (De < 1) were investigated, where the contribution of the vortices forming inside the drop to the additional mixing inside the reactor should be most noticeable. In the drop-based microfluidic device, discrete aqueous drops serving as reactors were generated by flow focusing using silicone oil as the continuous phase. Aqueous solutions of reagents were supplied through two different channels merging just before the drops were formed. In the continuous flow device, the reagents merged at a Tee junction, and the reaction was carried out in the outlet tube. Although continuous flow systems may face challenges such as particle concentration reduction due to deposition on the channel wall or fouling, they are often more practical for research due to their operational simplicity, primarily through the elimination of the need to separate the aqueous nanoparticle dispersion from the oil phase. The results demonstrate that both microfluidic approaches produced AgNPs of similar sizes when the hydrodynamic conditions defined by the values of De and the residence time within the reactor were similar.

The polarization state of light is critical for biological imaging, acousto-optics, bio-navigation, and many other optical applications. Phase shifters are extensively researched for their applications in optics. The size of optical elements with phase delay that are made from natural birefringent materials is limited; however, fabricating waveplates from dielectric metamaterials is very complex and expensive. Here, we present an ultrathin (14 nm) metallic phase shifter developed using nanoimprinting technology and the oxygen plasma ashing technique for visible and near-infrared wavelengths. The fabrication process can produce desirable metallic phase shifters with high efficiency, large area, and low cost. We demonstrate through a numerical simulation and experiment that the metallic phase shifter exhibits phase delay performance. Our results highlight the simplicity of the fabrication process for a metallic phase shifter with phase delay performance and offer important opportunities for creating high-efficiency, ultrathin polarizing elements, which can be used in miniaturized devices, such as integrated circuits.

When using a fiber optic gyroscope as the core measurement element in an inertial navigation system, its work stability and reliability directly affect the accuracy of the navigation system. The modeling and fault diagnosis of the gyroscope is of great significance in ensuring the high accuracy and long endurance of the inertial system. Traditional diagnostic models often encounter challenges in terms of reliability and accuracy, for example, difficulties in feature extraction, high computational cost, and long training time. To address these challenges, this paper proposes a new fault diagnostic model that performs a fault diagnosis of gyroscopes using the enhanced capsule neural network (iCaps NN) optimized by the improved gray wolf algorithm (NIGWO). The wavelet packet transform (WPT) is used to construct a two-dimensional feature vector matrix, and the deep feature extraction module (DFE) is added to extract deep-level information to maximize the fault features. Then, an improved gray wolf algorithm combined with the adaptive algorithm (Adam) is proposed to determine the optimal values of the model parameters, which improves the optimization performance. The dynamic routing mechanism is utilized to greatly reduce the model training time. In this paper, effectiveness experiments were carried out on the simulation dataset and real dataset, respectively; the diagnostic accuracy of the fault diagnosis method in this paper reached 99.41% on the simulation dataset; the loss value in the real dataset converged to 0.005 with the increase in the number of iterations; and the average diagnostic accuracy converged to 95.42%. The results show that the diagnostic accuracy of the NIGWO-iCaps NN model proposed in this paper is improved by 13.51% compared with the traditional diagnostic methods. It effectively confirms that the method in this paper is capable of efficient and accurate fault diagnosis of FOG and has strong generalization ability.