Abstract This paper presents an in-run virtual Coriolis force (VCF) method for direct closed-loop bandwidth characterization of force-to-rebalance (FTR) MEMS gyroscopes without an angular vibration table. Unlike prior VCF schemes that apply excitation to the force-feedback electrode and thereby disable the feedback loop, the proposed method exploits the quadrature-suppression electrode as a separate excitation channel, allowing VCF injection to coexist with the active FTR loop. Because the VCF acts on the quadrature ( Q ) carrier, the method measures the closed-loop response of the Q channel as a proxy for the in-phase ( I ) rate channel. A black-box calibration maps the VCF digital code to an equivalent angular rate using only the scale factor and the electrode force-coefficient ratio, with no mechanical parameter measurement required. Comparative frequency-response measurements over 0.1–20 Hz between the VCF method and a high-precision angular vibration table yield a Pearson correlation of R = 0.9932, with maximum relative error below 6.5% for excitation frequencies up to half the mode split ( 0.5 Δ f ); above 0.5 Δ f the deviation reaches up to 12.6% (near 16 Hz), which bounds the valid range of the present implementation.
Abstract In this work we report the integration of a thin SmCo-based permanent magnetic stack within a released silicon Micro-electro-mechanical systems (MEMSs) structure, using a fabrication process compatible with standard micromachining and release techniques. A W/SmCo/W multilayer (1 μ m total thickness) is embedded into a suspended magnetic-torque magnetometer through a trench-assisted lift-off process, followed by post-deposition annealing to promote magnetic crystallization. Magnetic characterization of patterned films shows a reduction in coercivity and remanent magnetization compared to continuous layers, attributed to edge and process-induced effects. Despite these limitations, the fabricated devices exhibit measurable magnetic actuation under weak external fields. In particular, a displacement sensitivity of approximately 15 nm mT − 1 is experimentally observed under an AC magnetic field, in reasonable agreement with theoretical estimates. The proposed approach demonstrates the feasibility of integrating high-coercivity permanent magnetic materials into released MEMS geometries, enabling compact magnetic functionality for sensing and actuation applications.
Abstract As a common engineering material, glass possesses several unique properties that make it promising for micro-electro-mechanical systems. However, micromachining glass structures is demanding because its hardness and brittleness challenge conventional manufacturing methods. Spark-assisted chemical engraving (SACE) has been proposed as an alternative process that uses localized high-temperature chemical etching to remove glass. Most conventional SACE machines based on Cartesian systems provide three degrees of freedom in tool motion, limiting machining mainly to 2D contours or 2.5D structures. This paper explores the use of a six-degree-of-freedom SACE system to machine inclined and multi-slope glass structures. When the tool electrode is tilted, the orientation change may alter local electrolyte flow and gas-film behaviors, contributing to non-uniform material removal, non-parallel cut walls, and angle-dependent errors. Several uncorrected cuts with programmed angles from 0° to 45° were analyzed via cross-sectional micrographs, revealing bottom-wall angular errors of up to 1.73°. A linear compensation model was established to estimate these errors and generate compensated tool commands, successfully reducing the residual angular error to within 0.26° in validation cuts. Finally, two compensated frustum structures demonstrate discrete multi-slope machining, with confocal-microscope estimates broadly consistent with the intended wall geometries.
Abstract The growing demand for compact camera systems has motivated the development of liquid-based optical elements as alternatives to mechanical components limited by frictional wear and bulk. Among these, liquid shutters have attracted increasing interest for active modulation of incident light. However, prior studies have focused primarily on actuation principles and optical performance, while long-term reliability under realistic operating conditions—repeated actuation, temperature variation, and mechanical vibration—remains largely unaddressed. This paper presents a liquid shutter driven by dielectrowetting (DEW) and systematically evaluates its environmental and operational reliability. The device consists of an opaque liquid-crystal (LC) droplet and a transparent silicone oil sealed within a thin microfluidic cell between two substrates, in which interdigitated indium tin oxide (ITO) electrodes generate a non-uniform fringing electric field that drives the droplet across the optical aperture. An auxiliary annular channel spacer is incorporated around the aperture to prevent bubble ingress under thermal expansion or vibration. The shutter was fabricated by wafer-level batch microelectromechanical systems (MEMS) processing. Optical transmittance, frequency-dependent contact-angle response, and voltage-dependent switching behavior were characterized to optimize the driving conditions, and the reliability was then evaluated along three axes. First, long-term cyclic actuation tests examined the durability of the switching response and light-blocking capability. Second, high- and low-temperature storage and operating conditions, together with thermal cycling, were defined with reference to the U.S. Department of Defense environmental test standard (MIL-STD-810H) to assess variations in response characteristics and structural stability. Third, droplet actuation stability and packaging-seal integrity were verified under reciprocating mechanical vibration. The proposed shutter maintained stable switching response and light-blocking capability under all three conditions, with no structural damage observed. Integration with a compact camera module demonstrated active modulation of incident light, confirming the device as a reliable shuttering solution for next-generation compact camera systems.
Abstract Material selection plays a critical role in the sensing performance of piezoelectric resonant microcantilever mass sensors, particularly when the sensor operates in different environments and multiple sensing mechanisms are considered. This study develops an analytical framework to investigate the effects of substrate and piezoelectric-layer materials on the performance of a segmented piezoelectric microcantilever mass sensor. Five substrate materials and five piezoelectric materials are systematically combined, resulting in 25 material configurations. Sensor performance is evaluated using three complementary metrics: frequency sensitivity Sf, relative vibration-amplitude variation ΔA/A, and relative piezoelectric output-current variation ΔI/I. The analysis is performed in both air and water, and the influence of material properties is further quantified using Sobol global sensitivity analysis. Finally, Pareto-based multi-objective analysis is employed to identify non-dominated material combinations. The results show that AlN–SiC provides the highest frequency sensitivity in both environments, with Sf values of 1.10 Hz/pg in air and 0.025 Hz/pg in water. In air, AlN–Poly-Si produces the largest amplitude and output-current variations, reaching 1023.22% and 978.25%, respectively, whereas ScAlN–SiC provides the highest corresponding responses in water, with 496.89% and 488.34%. The transition from air to water reduces the Sf, ΔA/A, and ΔI/I of AlN–SiC by approximately 97.7%, 79.2%, and 82.1%, respectively. Sobol analysis further reveals that the dominant material property depends on both the sensing metric and environment. Pareto analysis identifies three non-dominated combinations in air and two in water, demonstrating that no universal material combination simultaneously maximizes all sensing responses. The proposed framework therefore provides an environment- and objective-dependent strategy for material selection in piezoelectric resonant mass sensors.
