Micromachines最新文献

In this article, a chip-fed millimeter-wave high-gain antenna system with in-antenna power combining capability is presented. A low-profile resonant cavity antenna (RCA) array is fed by multiple spherical dielectric resonators (DRs), demonstrating its multi-feed capabilities. Each of the DRs is fed by two microstrip resonators on a planar circuit board. A printed superstrate is used in the proposed RCA as the partially reflecting superstrate (PRS), which makes the antenna profile small. To increase the directivity and gain, a 2 × 2 RCA array is developed. The demonstrated design shows a prominent peak gain of 25.03 dBi, a radiation efficiency of more than 80% and 3.38 GHz 3 db gain-bandwidth while maintaining a low profile. To steer the beam of the demonstrated 2 × 2 RCA array in a wide angular range with a low side-lobe-level, two planar all-dielectric passive beam steering metasurfaces have been designed and optimized. A detailed analysis of the optimization procedure is presented in this article. This numerical investigation is vitally important for realizing beam steering metasurfaces with suppressed side-lobe-level, wide bandwidth, excellent efficiency and less complexity.

This article presents the electrostatic actuation performance of micromirror arrays for intelligent active daylight control and energy management in green buildings using a capacitive-voltage (C-V) measurement technique. In order to understand how geometric hinge parameters, initial opening angles, and materials affect the overall efficiency and functionality of the system, micromirror arrays have been analyzed using C-V measurements considering (i) full and broken hinge structures, (ii) 90° and 130° initial tilt angles (Φ), and (iii) different material layer combinations. The measurement results indicate that both an increase in the Young's modulus of the applied materials and increasing the initial tilt angles increase the threshold voltages during the closing process of the micromirrors.

The pull-in and pull-out voltages are important characteristics of Capacitive Micromachined Ultrasound Transducers (CMUTs), marking the transition between conventional and collapse operation regimes. These voltages are commonly determined using capacitance-voltage (C-V) sweeps. By modeling the operating conditions of an LCR meter in COMSOL Multiphysics^®, we demonstrate that the measured capacitance comprises both static and dynamic capacitances, with the dynamic capacitance causing the appearance of a peak in the effective C-V curve. Furthermore, Laser Doppler Vibrometer (LDV) measurements and electromechanical simulations indicate the occurrence of collapse-snapback phenomena during the C-V sweeps. This study, through advanced simulations and experimental analyses, demonstrates that the transient membrane behavior significantly affects the apparent capacitance-voltage characteristics of electrostatically actuated Micro-Electromechanical Systems (MEMS).

In recent years, the need for future developments in sensor technology has arisen out of the changing landscape, such as pollution monitoring, industrial safety, and healthcare. MXenes, a 2D class of transition metal carbides, nitrides, and carbonitrides, have emerged as a particularly promising group in part due to their exceptionally high conductivity, large area, and tunable surface chemistry. Proposed future research directions, including material modification and novel sensor designs, are presented to maximize Ti₃C₂T_x MXene-based sensors for various gas sensing applications. While recent progress in Ti₃C₂T_x MXene-based gas sensors is reviewed, we consolidate their material properties, fabrication strategy, and sensing mechanisms. Further, the significant progress on the synthesis and applications of Ti₃C₂T_x MXene-based gas sensors, as well as the innovative technologies developed, will be discussed in detail. Interestingly, the high sensitivity, selectivity, and quick response times identified in recent studies are discussed, with specificity and composite formation highlighted to have a significant influence on sensor performance. In addition, this review highlights the limitations witnessed in real-life implementability, including stability, the possibility of achieving reproducible results, and interaction with currently available technologies. Prospects for further work are considered, emphasizing increased production scale, new techniques for synthesis, and new application areas for Ti₃C₂T_x MXenes, including electronic nose and environmental sensing. Contemplating the existing works, further directions and the development framework for Ti₃C₂T_x MXene-based gas sensors are discussed.

This paper presents a novel microfluidic device that integrates dielectrophoresis (DEP) forces with a membrane filter to concentrate and trap microparticles in a narrow region for enhanced optical analysis. The device combines the broad particle capture capability of a membrane filter with the precision of DEP to focus particles in regions optimized for optical measurements. The device features transparent indium tin oxide (ITO) top electrodes on a glass substrate and gold (Au) bottom electrodes patterned on a small area of the membrane filter, with spacers to control the gaps between the electrodes. This configuration enables precise particle concentration at a specific location and facilitates real-time optical detection. Experiments using 0.8 μm fluorescent polystyrene (PS) beads and Escherichia coli (E. coli) bacteria demonstrated effective particle trapping and concentration, with fluorescence intensity increasing proportionally to particle concentration. The application of DEP forces in a small region of the membrane filter resulted in a significant enhancement of fluorescence intensity, showcasing the effectiveness of the DEP-enhanced design for improving particle concentration and optical measurement sensitivity. The device also showed promising potential for bacterial detection, particularly with E. coli, by achieving a linear increase in fluorescence intensity with increasing bacterial concentration. These results highlight the device's potential for precise and efficient microparticle concentration and detection.

Point-of-care (POC) testing has revolutionized diagnostics by providing rapid, accessible solutions outside traditional laboratory settings. However, many POC systems lack the sensitivity or multiplexing capability required for complex diseases. This study introduces an LED-based fluorescence reader designed for POC applications, enabling multiplex detection of lupus nephritis (LN) biomarkers using a biomarker microarray (BMA) slide. The reader integrates an LED excitation source, neutral density (ND) filters for precise intensity control, and onboard image processing with Gaussian smoothing and centroid thresholding to enhance signal detection and localization. Five LN biomarkers (VSIG4, OPN, VCAM1, ALCAM, and TNFRSF1B) were assessed, and performance was validated against a Genepix laser-based scanner. The LED reader demonstrated strong correlation coefficients (r = 0.96-0.98) with the Genepix system for both standard curves and patient samples, achieving robust signal-to-noise ratios and reproducibility across all biomarkers. The multiplex format reduced sample volume and allowed simultaneous analysis of multiple biomarkers. These results highlight the reader's potential to bridge the gap between laboratory-grade precision and POC accessibility. By combining portability, cost-effectiveness, and high analytical performance, this fluorescence reader provides a practical solution for POC diagnostics, particularly in resource-limited settings, improving the feasibility of routine monitoring and early intervention for diseases requiring comprehensive biomarker analysis.

Dermal drug delivery presents a significant challenge for poorly soluble active compounds like curcumin, which often struggle to penetrate the skin barrier effectively. In this study, the dermal penetration efficacy of curcumin nanocrystals and bulk suspensions when applied to skin using microneedles of varying lengths-0.25 mm, 0.5 mm, and 1.0 mm-was investigated in an ex vivo porcine ear model. The findings revealed that all formulations, in conjunction with microneedle application, facilitated transepidermal penetration; however, the combination of microneedles and curcumin nanocrystals demonstrated the highest efficacy. Notably, the 1.0 mm microneedle length provided optimal penetration, significantly enhancing curcumin delivery compared with bulk suspensions alone. Additionally, even the use of 0.25 mm microneedles resulted in a high level of efficiency, indicating that shorter microneedles can still effectively facilitate drug delivery. Overall, this study underscores the potential of microneedle technology in improving the transepidermal absorption of poorly soluble actives like curcumin, suggesting that the integration of nanocrystals with microneedles could enhance the therapeutic effects of topical curcumin applications.

Biological bone screws play an important role in fixing fractures and bone defects. The machining of helical grooves on xenogenic materials is a key part of fabricating biological bone screws. The fabrication of helical grooves on bovine bone using micro-abrasive air jets was investigated in this paper. The helical groove shapes were classified and their formation mechanisms were studied. Analyses of the material removal mechanism and the effect of process parameters on the groove shapes were carried out. The results show that the helical grooves could be effectively machined using micro-abrasive air jets with a spring mask. The shapes of the helical grooves could be classified as U-, V-, and W-shaped. Cracks that propagated along the cement line may have led to the formation of a slot. Meanwhile, cracks that propagated in the interstitial lamella may have led to the formation of ridges. The slots and ridges resulted in the appearance of stripes on the groove bottom. The cracks propagated along the axial direction of the osteon at the same time as it propagated into the osteon, leading to the formation of dimples on the groove sidewall. The experimental method proposed in this study can be regarded as a suitable method to fabricate helical grooves on bones.

Macroporous silicon is a promising substrate in the field of optics, electronics, etc. In this paper, highly ordered macropore arrays were fabricated in p-type silicon wafers by electrochemical etching using a double-tank cell. The effect of the silicon resistivity, etching voltage and etching time on the pore morphology was investigated and the influence mechanism was analyzed. The pore diameter would decrease with the increase in the silicon resistivity and the decrease in the etching voltage, due to the increase in the space charge region width (SCRL). The pore depth would increase with the resistivity and the voltage. However, too high resistivity would cause insufficiency at the pore tips and too high voltage would cause pore splitting, which may cause a decrease in the pore depth. Then, the aspect ratio of 21 can be obtained on the silicon wafer with a resistivity of 50-80 Ω·cm at the etching voltage of 5 V with a maximum etching rate of about 0.92 μm/min.

Carbon fiber/polyether ether ketone (CF/PEEK) is widely used in aerospace, transportation, and other high-end industries for its light weight, high strength, and recyclability. However, its inherently brittle-ductile two-phase structure presents challenges in processing CF/PEEK. This paper introduces a laser-assisted milling method, wherein four types of CF/PEEK unidirectional plates (0°, 45°, 90°, and 135°) are milled under varying laser powers and spindle speeds. The results are compared with conventional milling (CM) techniques, based on cutting forces, temperatures, surface roughness, and damage defects. The cutting force, temperature, and surface quality were optimal at a fiber direction of 0° and were least favorable at 90° under identical machining conditions. When the fiber direction was 90°, the milling temperatures at 400 W and 500 W laser power decreased by 19.8% and 7.9%, respectively, while the average values of Fx and Fy decreased by 20.5% and 9.55%, compared to conventional milling. Furthermore, the laser-assisted milling method significantly reduces surface defects and improves surface roughness. In CF/PEEK composites, brittle fracture is the primary material removal mechanism, with damage characteristics such as fiber fracture, fiber pullout, and fiber/matrix debonding. The optimal parameter combination is a 0° fiber orientation, 400 W laser power, and a spindle speed of 4000 rpm. This study provides theoretical and technical support for the high-quality processing of CF/PEEK composites.