Jinling Yang

Compact current sensors near distributed loads must resolve both AC and DC components while maintaining electrical isolation, yet cantilever sensors commonly rely on dynamic or resonance-dependent readout. To address this limitation, this work presents a microelectromechanical systems current sensor based on a magnet-integrated piezoresistive microcantilever, AC bridge excitation and digital lock-in amplifier demodulation. A tip-mounted neodymium–iron–boron magnet converts the field gradient of a conductor pair into cantilever loading, and doped-silicon piezoresistors convert the resulting quasi-static stress into a Wheatstone-bridge signal. For the geometry selected by surrogate-assisted optimization, the theoretical bridge-noise-limited force resolution is 2.09 nN over 1–1000 Hz, equivalent to a current resolution of 0.73 mA. Magnet loading shifts the first resonance from 3.34 kHz to 507 Hz, which remains compatible with DC and 50 Hz quasi-static operation. A prototype was characterized over 0–10 A at 50 Hz, giving 0.15% linearity error, 0.38% hysteresis and 0.064% repeatability, and its response remained approximately linear in an extended sweep to 50 A. For DC measurement, the carrier-excited readout gives a root-mean-square bridge-referred noise of 0.114 μ V, compared with 0.454 μ V for direct low-frequency readout of the same bridge. A source-limited 0–2 A DC calibration yields a sensitivity of 141.34 μ V A − 1 with 0.81% linearity error. These results demonstrate that static-strain magnetic transduction enables compact AC/DC current measurement without resonance-dependent DC recovery.

In the production and manufacturing of non-ferromagnetic materials, precise control of motion speed and accurate detection of defects are critical to ensuring the quality and reliability of the final product. However, existing sensors face limitations in practical applications, as they are unable to simultaneously measure the motion velocity and detect defects in non-ferromagnetic thin plate materials. To address this issue, this study presents a Lorentz force sensor based on the principle of the Lorentz Force Particle Analyzer (LFPA), which is capable of simultaneously measuring the motion velocity and micro-defects in non-ferromagnetic thin plate materials. To enhance the sensor’s detection sensitivity while mitigating the effects of the permanent magnet’s weight, a detailed analysis of the influence of support beam parameters on stiffness was conducted, and the folded beam parameters were optimized through numerical simulations. Static performance tests confirmed that the sensor can accurately detect force variations on the order of micro-Newtons. Experimental testing demonstrated that the sensor is capable of detecting planar defects as small as 500 μm in 0.1 mm thick copper foil. Compared to similar sensors, this sensor can detect defects approximately 3.5% of the size of those detectable by other sensors, thereby exhibiting higher sensitivity. The design and implementation of this sensor significantly improve the accuracy and operational ease of on-site measurements in the production and manufacturing of non-ferromagnetic thin plate materials, providing technical support for optimizing production processes and enhancing product quality.

Copper and aluminum foils serve as predominant materials in fluid collectors, and defects within them can significantly impact the electrochemical performance of cells. However, existing methods for detecting defects within non-ferromagnetic thin metals, such as copper and aluminum foils, have several limitations. This study aims to address the need for detecting micrometer-scale defects on 0.1 mm copper foils, aligning with industrial field requirements. We devised an inspection device based on the induced magnetic field detection principle and explored the impact of copper foil undulations on micrometer-scale defect detection using COMSOL modeling. Subsequently, we introduced a coherent cumulative-differential algorithm to effectively mitigate the influences of circuit noise and sampling heave noise on defect signals. Consequently, the signal-to-noise ratios of 100- and 200-micron defect signals were significantly improved by 157% and 234%, respectively. This approach shows promise for detecting micrometer-scale defects in non-ferromagnetic thin metals and lays a robust foundation for future defect identification and inversion endeavors.

This work presents a silicon-based capacitively transduced width extensional mode (WEM) MEMS rectangular plate resonator with quality factor (Q) of over 10,000 at a frequency of greater than 1 GHz. The Q value, determined by various loss mechanisms, was analyzed and quantified via numerical calculation and simulation. The energy loss of high order WEMs is dominated by anchor loss and phonon-phonon interaction dissipation (PPID). High-order resonators possess high effective stiffness, resulting in large motional impedance. To suppress anchor loss and reduce motional impedance, a novel combined tether was designed and comprehensively optimized. The resonators were batch fabricated based on a reliable and simple silicon-on-insulator (SOI)-based fabrication process. The combined tether experimentally contributes to low anchor loss and motional impedance. Especially in the 4th WEM, the resonator with a resonance frequency of 1.1 GHz and a Q of 10,920 was demonstrated, corresponding to the promising f × Q product of 1.2 × 10¹³. By using combined tether, the motional impedance decreases by 33% and 20% in 3rd and 4th modes, respectively. The WEM resonator proposed in this work has potential application for high-frequency wireless communication systems.

This work investigates the dominant loss mechanisms of the multi-frequency whispering gallery mode (WGM) resonators theoretically and experimentally, which provides a deep understanding about the working principles of the devices and guidance on their high-end applications. For the first time, the distinct Akhiezer damping (AKE) effects on various order WGMs were comprehensively clarified. At atmosphere, the air damping, which is conventionally expected to be negligible in high-order bulk acoustic wave (BAW) modes, is nonnegligible for all the WGMs. In vacuum, substantial Q enhancements more than two times were obtained. The high-order WGMs benefit more f × Q improvement from the high vacuum than the low-order ones, achieving a promising f × Q product of 1.16 × 10¹³. What’s more, the Q dynamics over a wide temperature range were characterized, which matched well with the theoretical analysis. The AKE is comparable with anchor loss in low-order modes, while it becomes dominated in the high-order ones. Therefore, the high-order WGMs exhibit higher Q enhancements at cryogenic temperatures. An excellent f × Q product up to 5.91 × 10¹³ was implemented at 7 K.

This paper presents a novel Π-shaped bulk acoustic resonator (ΠBAR) with low bias voltages. Concave flanges were coupled with straight beams to effectively enlarge the transduction area. A silicon-on-insulator(SOI)-based fabrication process was developed to produce nanoscale spacing gaps. The tether designs were optimized to minimize the anchor loss. With a substantially improved electromechanical coupling coefficient, the high-stiffness ΠBAR can be driven into vibrations with low bias voltages down to 3 V. The resonator, vibrating at 20 MHz, implements Q values of 3600 and 4950 in air and vacuum, respectively. Strategies to further improve the resonator performance and robustness were investigated. The resonator has promising IC compatibility and could have potential for the development of high-performance timing reference devices.

This work presents a novel ultra-high frequency Lamb mode Aluminum nitride piezoelectric resonator with enhanced quality factors ( Q ). With slots introduced in the vicinity of the tether support end, the elastic waves leaking from the tether sidewalls can be reflected, which effectively reduces the anchor loss while retaining size compactness and mechanical robustness. Comprehensive analysis was carried out to provide helpful guidance for obtaining optimal slot designs. For various resonators with frequencies ranging from 630 MHz to 1.97 GHz, promising Q enhancements up to 2 times have all been achieved. The 1.97 GHz resonator implemented excellent f × Q product up to 6.72 × 10 ¹² and low motional resistance down to 340 Ω, which is one of the highest performances among the reported devices. The devices with enhanced Q values as well as compact size possess potential application in advanced radio frequency front end transceivers.

This paper presents a simple and reliable routine for batch fabrication of wear-resistant and conductive probe with a PtSi tip. The fabrication process is based on inductively coupled plasma (ICP) etching, metal evaporation, and annealing. Si tips with curvature radii less than 10 nm were produced with good wafer-level uniformity using isotropic etching and thermal oxygen sharpening. The surface roughness of the etched tip post was reduced by optimized isotropic etching. The dependence of the platinum silicide morphology on annealing conditions were also systematically investigated, and conductive and wear-resistant probes with PtSi tips of curvature radii less than 30 nm were batch fabricated and applied for scanning piezoelectric samples.