This paper presents an electrothermally actuated platform for in-situ tensile testing of nanoscale films, designed to overcome two critical challenges in on-wafer mechanical testing: thermal effects on the specimen and low accuracy of manual displacement readout. Athermal isolation structure is implemented to suppress heat transfer from the V-shaped actuator to the specimen, and a subpixel displacement measurement algorithm is developed for high-precision automated measurement. Experimental results show that, with the thermal isolation structure, the actuator reaches $151.49~^{\circ }$ C while the specimen temperature remains at $20.73~^{\circ }$ C at 1.5V, reducing the relative deviation of the measured Young’s modulus from over 10% to less than 1%. The proposed subpixel measurement algorithm achieves $\gt 0.1~\mu $ m resolution; linear fitting of maximum displacement vs. squared driving voltage yields R ${}^{2} \gt 0.99$ , confirming its accuracy. Tensile fracture tests reveal significant regional variation in fracture strength across the wafer. The proposed platform enables reliable on-wafer process quality monitoring in MEMS fabrication.[2026-0057]
The mechanical frequency locking (MFL) phenomenon in the nonlinear resonant system can overcome the dependent effect between response frequency and amplitude caused by stiffness hardening through the internal resonance, which is beneficial for enhancing the frequency stability of the resonant system and improving the dynamic performance of the resonant device. This study reports a high-resolution MEMS coupled resonant differential accelerometer based on the MFL phenomenon. Firstly, the electrostatic-driven mechanical coupled MEMS resonant accelerometer is designed and fabricated, which can utilize the DC driving voltage of the inner resonant beam to adjust the dynamic characteristics and sensitivity of the device. Through open-loop experiments and theoretical predictions, it is discovered that a 1:1 internal resonance between the inner and outer resonant beams can be induced via the mechanical coupling component, and a MFL phenomenon is generated. Then, the sensitivity and reliability of MEMS resonant accelerometer under different resonant conditions are tested in both open-loop and closed-loop experiments. Compared with traditional resonance detection methods, the accelerometer based on MFL phenomenon has better reliability and can suppress the detection errors caused by fluctuations in the AC driving voltage. Typically, it is found that the MFL phenomenon improved the frequency stability of the accelerometer and reduced the Allan deviation of the response frequency. Based on this phenomenon, a high-resolution acceleration detection principle is proposed, which can reduce the intrinsic resolution of the device to 3.7 ug. The detection principle proposed in this article is of great significance for the development of nonlinear resonant sensors. [2026-0039]
The temperature field across MEMS resonant accelerometers exhibits nonuniform and dynamic distributions under practical operating conditions, which makes temperature monitoring and thermal drift compensation in silicon accelerometers challenging. The ring-down driving scheme enables real-time quality factor monitoring for accurate in-situ temperature measurement, while frequency ripple induced by the amplitude-stiffening (A-S) effect degrades frequency stability. Addressing this problem, we propose a ring-down driving scheme with active ripple suppression (ARS), where the real-time monitored quality factor serves as a virtual thermometer, and the resonant frequency ripple is suppressed through electrostatic stiffness modulation. During continuous ring-down operation, the amplitude of the sensing signal is utilized as a phase stamp to continuously adjust the bias voltage of the driving signal via the dual-LUT and employ a calibration circuit based on P-type iterative learning control (ILC) to calibrate the feedback compensation relationship. The results of the experiment demonstrate that the proposed technique reduced the peak-to-peak frequency ripple from 7.3 Hz to 0.8 Hz, a suppression of 89% and achieved a harmonic suppression ratio of 41.9 dB, representing an improvement of $18.8\times $ . The proposed technique in generalization experiments achieved an average harmonic suppression ratio of 36.1 dB with a standard deviation of 5.4 dB. Additionally, it enables near in-situ temperature monitoring with low hysteresis, with a temperature resolution better than 0.2 °C within 1 Hz bandwidth through quality measurement. For applications of resonant accelerometers, the proposed ARS method achieves an acceleration resolution of 2.3 mg within a 10 Hz bandwidth and a bias stability of 1.0 mg after temperature compensation over the temperature range of 0 °C to 45 °C. The proposed system enables both real-time and accurate in-situ temperature tracking while improving acceleration resolution.[2026-0068]
This work presents a 5 MHz microelectromechanical systems (MEMS) oscillator based on a high-quality factor ( $Q_{\mathrm {unloaded}} \gt 50$ ,000) lateral extensional (LE) mode Aluminum Nitride (AlN)-on-silicon (Si) resonator for stable clock applications. The resonator is designed to have a turn-over temperature (ToT) above $100~^{\circ }$ C and is fabricated on a $350~\mu $ m thick single-crystal Si substrate to achieve high $Q$ while its lateral dimensions are optimized to obtain a low motional impedance. To improve frequency stability, the oscillator is operated under high vacuum and evaluated using two thermal-control configurations. The single-oven configuration utilizes an integrated heater on the resonator and applies a fixed integrated-heater bias near the ToT, while the dual-oven configuration additionally stabilizes the environmental temperature fluctuations within the vacuum-chamber using controlled external heating. Both configurations reach an Allan deviation (ADEV) of approximately $1.7\times 10^{-10}$ at $\tau =1$ s, demonstrating strong short-term stability enabled by the high- $Q$ resonator. However, the dual-oven configuration suppresses the increase in ADEV at long averaging times, maintaining an ADEV of approximately $1.6\times 10^{-10}$ at $\tau =1000$ s compared with $9.5\times 10^{-9}$ for the single-oven operation, and exhibiting an average net drift rate of 0.85 ppb/h over 32 h. The results distinguish the roles of the high- $Q$ resonator and external chamber thermal stabilization in achieving short- and long-term frequency stability, respectively.[2026-0044]
This paper presents the experimental characterization and optimization of palladium (Pd)-coated aluminum nitride (AlN) laterally vibrating resonators (LVRs) for high-sensitivity hydrogen (H2) detection. The sensing mechanism relies on hydrogen-induced biaxial compressive stress in the Pd film, which shifts the resonant frequency through stress-frequency transduction, enabling compact, selective, and high-resolution H2 monitoring for leak-detection applications. Pd-coated LVRs operating from 123 to 396 MHz were fabricated on a single 4-inch wafer, enabling a controlled study of the combined effects of operating frequency, Pd thickness, and residual stress on electromechanical performance and sensing response. Quality factors reaching $Q = 1625$ and electromechanical coupling coefficients reaching $k_{t}^{2} = 1.94\%$ were achieved, representing a $2.7\times $ improvement in Q over prior ScAlN-based implementations. Sensitivity increases monotonically with frequency (15 to 54 Hz/ppm at 123–396 MHz for 100 nm Pd) and with Pd thickness ( $8.5\times $ from 100 to 200 nm). Residual stress is identified as a previously underreported optimization lever, producing a $2.6\times $ sensitivity enhancement for the same Pd thickness. The 317MHz device with 150 nm Pd is identified as the optimal design point ( $Q = 1411$ , $k_{t}^{2} = 0.92\%$ ), achieving a peak sensitivity of 772Hz/ppm in the low-concentration regime with $t_{90} \approx 10$ min, establishing Pd-coated AlN LVRs among the most sensitive resonant H2 sensors reported to date.[ 2026-0081]
To overcome the intrinsic narrowband limitation of high-Q MEMS piezoelectric speakers, a stiffness-modulated multi-resonant array strategy is proposed to broaden the effective acoustic bandwidth. By locally modifying the boundary stiffness of triangular cantilever diaphragms through etched grooves of different lengths, the resonant frequencies of individual speaker units are intentionally distributed within a target frequency band. A theoretical framework based on single-degree-of-freedom resonance modeling is established to analyze the phase–frequency behavior of each unit and to clarify how appropriate resonance spacing suppresses inter-unit phase mismatch. The analysis reveals that closely spaced resonances confine the phase transition regions, thereby preventing destructive interference of volume displacement between adjacent units and enabling constructive superposition over a wider frequency range. Finite element simulations incorporating an IEC 711 ear-coupler model validate the resonance allocation mechanism and predict broadened acoustic response. Experimental measurements under 1 Vrms AC excitation with 15 V DC bias demonstrate an SPL exceeding 120 dB across 12.5–18 kHz, confirming the effectiveness of the proposed resonance-dispersion design. This work provides a physically grounded strategy for rationally allocating resonant frequencies in multi-unit MEMS speaker arrays and offers a practical route toward wideband high-SPL acoustic transducers.[2025-0173]
Continuous cuffless blood-pressure (BP) monitoring requires compact sensors capable of tracking arterial diameter with high repeatability. Time-resolved photoacoustic (PA) sensing is attractive because vessel diameter is directly encoded in the temporal separation between the anterior- and posterior-wall arrivals in the PA A-line signal, eliminating the need for beamforming and image reconstruction. Here, we present a compact (2.5 mm $\times\,\, 5$ mm) multi-frequency piezoelectric micromachined ultrasonic transducer (PMUT) receiver fabricated by a cavity silicon-on-insulator (CSOI) process. The high-fill-factor design provides three receive bands centered at approximately 3.5, 5.5, and 11 MHz, with PA −6 dB fractional bandwidths of 126%, 103%, and 110%, respectively. Owing to the large effective acoustic aperture and low-noise front-end readout, the low-frequency array achieves a noise-equivalent pressure (NEP) of $2.9~\boldsymbol {mPa}/\sqrt { \boldsymbol {Hz}}$ at 3.5 MHz. Using a compact 532 nm pulsed laser delivering $\sim 5~\mu $ J/pulse, the system resolved vessel phantoms with inner diameters down to 1.0 mm at a depth of 5 mm in an optically clear medium, detected PA signals up to 40 mm in clear media, and maintained vessel detection up to 6 mm in a scattering tissue-mimicking medium. These results demonstrate that complementary low-, mid-, and high-frequency PMUT arrays can jointly provide penetration depth and diameter resolution within a compact footprint, supporting the development of wearable PA sensors for cuffless vascular monitoring. [2026-0042]
This paper presents the monolithic three-dimensional (M3D) integration of a non-volatile out-of-plane MEMS memory directly above the complementary metal-oxide-semiconductor (CMOS) back end of line (BEOL) for reconfigurable logic applications. The integration process combines chemical–mechanical polishing (CMP) to planarize the BEOL surface with low-temperature electroplating to maintain full compatibility with the post-CMOS thermal budget. By fabricating the MEMS memory above the BEOL rather than constructing the device directly from BEOL metal layers, this approach overcomes the geometric and material constraints of prior in-plane BEOL-integrated MEMS memories and significantly reduces their typical k $\Omega $ –level on-resistance. The integrated see-saw MEMS memory demonstrates near-zero off-state leakage, retention exceeding $10^{6}$ seconds, and a low on-resistance of approximately $240~\Omega $ , with operation over 184 switchingcycles. These characteristics represent a substantial improvement over previous BEOL-integrated MEMS memories. Furthermore, a 2-input look-up table (LUT) implemented using four of these memory cells successfully performs AND, OR, and XOR logic operations by programming their non-volatile states, confirming on-chip reconfigurable logic capability. Overall, this work provides the first demonstration of an out-of-plane MEMS memory monolithically integrated on a CMOS platform and establishes a practical pathway toward CMOS-MEMS hybrid circuits. The results highlight the potential of such integration for future ultra-low-power, high-density, and reconfigurable logic systems.[2025-0229]
Copper microbeams are critical structural elements in microelectromechanical systems (MEMS), micro-sensors, and flexible electronic assemblies. However, their fabrication at microscales remains challenging due to copper’s high ductility and the dominance of size-effect phenomena. This study investigates the feasibility of high-speed micromilling for producing copper microbeams with widths ranging from $30~\upmu $ m down to $10~\upmu $ m. Experiments were conducted by varying feed per tooth and spindle speed to evaluate dimensional accuracy and burr formation mechanisms. Results show that $20~\upmu $ m microbeams fabricated at 20,000 rpm achieved dimensional deviations within 0.65–2.8%, demonstrating stable shearing-dominated cutting. In contrast, fabrication of $10~\upmu $ m beams was strongly influenced by the transition from shearing to ploughing, leading to pronounced burr formation and dimensional instability. Burr height decreased with an increase in feed rate from 1 to $2~\upmu $ m/tooth, but increased at $3~\upmu $ m/tooth, showing a narrow process window for burr-minimized fabrication. These findings establish the fabrication limits and process window for precision micromilling of copper microstructures and provide mechanistic insight into microscale material removal behavior relevant to MEMS device manufacturing. [2026-0034]
Salinity, temperature and depth (CTD) are fundamental environmental parameters in oceanography, which play a critical role in marine scientific research, ecological conservation, and resource exploration. CTD sensors fabricated using micro-electro-mechanical system (MEMS) technology offer significant advantages, including small size, low power consumption, cost-effectiveness, and high performance, making them a prominent research focus over the past decade. In this study, we developed a miniaturized integrated CTD MEMS sensor chip by combining three sensing elements: a piezoresistive pressure sensor, a four-electrode conductivity sensor, and a platinum resistance temperature sensor, utilizing a standardized MEMS fabrication process. The chip has a size of $2\times 2\times 0.9$ mm3. Our best chip shows conductivity (for salinity) resolution of $\sim ~0.0005$ mS/cm, temperature resolution of $\sim ~0.0027~^{\circ }$ C and pressure resolution (for depth) of $\sim $ 0.67 kPa (6.7 cm water depth). An AI (artificial intelligent) algorithm is also employed to enhance the performance of the CTD sensor. After optimization, the accuracies of the sensors decreased from 0.02°C to 0.004°C (temperature sensor), from 0.02 MPa to 0.002 MPa (pressure sensor), from 0.08 mS/cm to 0.02 mS/cm (conductivity sensor), respectively. Chips with moderate or lower performance (due to the natural distribution induced by process deviation) thus got enhance with comparable performance with the best chips. The current report indicates that the MEMS CTD sensor, embedded with the AI algorithm, might be a viable route towards future marine applications.[2026-0026]
This work presents the first demonstration of a thickness-field-excited (TFE) lithium niobate (LN) flexural mode piezoelectric transducer. A $\mathrm {300~\mu \text {m} }$ -thick periodically poled piezoelectric (P3F) 36Y LN bimorph is used to prototype. The transducer features a robust mechanical structure and optimized design, achieving a high electromechanical coupling coefficient ( $k^{2}$ ) of 5% with a flexural-mode resonance of 115 kHz. Laser Doppler vibrometer (LDV) measurements indicate a good mode shape, whereas impedance measurements indicate excellent dielectric loss. The resulting TFE transducer exhibits high performance, linearity, and integrability, indicating promise as a low-loss, robust piezoelectric transducer platform. These results motivate a closer examination of the TFE LN piezoelectric micromachined ultrasonic transducer (PMUT) with a high capacitance density.[2026-0063]
For the first time, it is shown that a pinched hysteresis response can be observed in a MEMS resonator when subject to parametric modulation and Duffing nonlinearity. The resultant memristor-like device operates in an open-loop configuration, without the need for a phase-locked loop based feedback control mechanism, to generate discontinuities in response to a stiffness perturbation. This simplifies the peripheral electronics needed to realize memristor-like operation using MEMS resonators, which is a key to realizing practical devices based on this approach. As alternatives to classical computing architectures begin to emerge, we see this work as providing a foundation towards integrated sense, memory, and compute functionality within a single device, which is essential for emerging computing paradigms such as neuromorphic and in-sensor computing.[2026-0062]
We demonstrate an acoustic radiation force (ARF)–driven microspeaker in which a polyimide (Kapton) membrane is actuated by amplitude-modulated ARF generated by a piezoelectric micromachined ultrasonic transducer (pMUT) array to produce audible sound. The ARF mechanism is first validated through two preliminary experiments: 1) quantification of the force generated by a single pMUT using a lightweight cantilever; and 2) excitation of a Kapton membrane at its natural frequency, confirming ARF-to-mechanical motion transduction via ear-simulator measurements. Building on these results, a 14-element pMUT array achieves peak membrane velocities up to 1.1 cm/s at 8 V and produces sound-pressure levels over the 20 Hz–20 kHz range, including 105 dB at 10 kHz and $\ge 60$ dB at 400 Hz (18 V). The measured velocity exhibits a sub-quadratic dependence on drive voltage (V ${}^{1}\cdot ^{28}$ , R ${}^{2} =99.4$ %), indicating an amplitude-dependent reduction in efficiency during array operation. These results establish ARF-based actuation as a viable approach for MEMS microspeakers, while suggesting that higher carrier frequencies and optimized membrane designs may further improve low-frequency performance. [2026-0016]
We present a wafer-scale fabrication strategy for three-dimensional (3D) bilayer high–aspect-ratio patterns based on nanoimprint lithography (NIL). The process integrates laser direct-writing grayscale lithography for precise definition of bilayer profiles, followed by two sequential cycles of pattern transfer into a chromium (Cr) hard mask and deep reactive ion etching (DRIE), thereby forming self-aligned 3D patterns on silicon. A flexible polydimethylsiloxane (PDMS) mold replicated from the etched silicon mold enables high-fidelity duplication of the 3D features through ultraviolet nanoimprint lithography (UV-NIL). This approach offers outstanding design flexibility and precise morphological control. Combining process stability, structural precision, and versatility, this approach establishes a reliable route for nanoimprint fabrication of multilayer high–aspect-ratio 3D structures. [2026-0038]
New manufacturing routes and materials need to be constantly developed to improve the performance of a new type of gas detector–a high-gain and fast-timing micro-pattern gaseous detector (MPGD)–which works as a gas electron multiplier. The cylindrical symmetry of microholes in perforated electrodes is desired in such detectors to ensure denser electric field lines and higher sensitivity, as well as stability of the detector. On the other hand, the probability of discharge between the electrodes arises at high gains. The discharge issue can be solved using a resistive layer with controlled electrical conductivity. In this work, we developed an ultrashort pulse laser ablation route to produce electrodes based on microstructuring of polyimide (Kapton™) foil that allows avoiding the wet-etching process and opens another level of variability in hole diameters and distribution over the surface. Femtosecond laser ablation was used to micromachine multiple arrays of cone-shaped through holes with narrowing diameters in an area of $3\times 3$ mm2 in polyimide foil. By employing an unbalanced direct current magnetron sputtering method obtained micropatterned polyimide surface was covered with a diamond-like carbon layer of 50 nm thickness and $4.36~\pm ~2.49$ M $\Omega $ /sq average sheet resistance ( $R_{\mathbf {S}}$ ) as a resistive layer, which would be reconcilable with the technologies used in the fast-timing MPGD detectors.[2025-0230]
This study presents the design, fabrication, and comprehensive characterization of as-deposited magnetostrictive FeCo and FeCoCr thin films based micro-cantilevers. Chromium (Cr) was systematically doped into the FeCo thin films to investigate its effect on their magnetostrictive properties. The magnetostriction coefficient was precisely evaluated using a non-contact stroboscopic Laser Doppler Vibrometer (LDV) setup, where a Si/SiO2/FeCoCr microcantilever served as the mechanical transducer, converting magnetic energy into mechanical energy. The microcantilever was subjected to an in-plane external DC magnetic field, oriented either parallel or perpendicular to its length. Results revealed that increasing Cr content significantly enhanced the magnetostrictive response, achieving a peak value of magnetostriction approximately 151 ppm. Additionally, Cr incorporation improved the films mechanical, electrical, and structural properties, yielding a saturation magnetization of about 1172 emu/cm3, a residual tensile stress of + 85.53 MPa, a resistivity of around $85.54~\mu \Omega $ -cm, and an average grain size of ~35 nm. These properties establish that FeCoCr thin films are promising material for micro-magnetic sensors and as efficient alternatives for electrode materials for the MEMS applications.[2026-0033]
In this work, a novel design scheme of on-chip frequency shifting is proposed and applied to acoustic resonators for the first time. On the same chip with first-order antisymmetric mode (A1-mode) resonators on 128° Y-cut lithium niobate (LiNbO3 or LN) thin film, LN based capacitors are proposed and realized by rotating the in-plane periodic direction of interdigitated transducer (IDT) electrodes to align the electric field direction at 90° relative to the +X axis. In a ladder-type topology, the series branch achieves an upward shift of the series resonant frequency by connecting an A1-mode resonator in series with an on-chip LN capacitor, while the shunt branch realizes a downward shift of the parallel resonant frequency by connecting an A1-mode resonator in parallel with a capacitor or rotating the IDT electrodes to a specific angle. By aligning these two frequencies through careful design, an acoustic filter is successfully implemented. Compared to traditional A1-mode filters, which rely on differentially localized etching to achieve frequency shifts in the series branch, the proposed novel design scheme reduces at least one photolithography and etching step, thereby greatly lowering process complexity and improving yield. Through this approach, this work demonstrates a high frequency (in the centimeter-wave or cmWave band) filter operating at 14.3 GHz with an insertion loss (IL) of 3.6 dB, a bandwidth of 961 MHz (FBW of 6.7%), and an out-of-band rejection (OoB) of 14 dB. This proves the validity of the pure layout-design based frequency shifting mechanism and enables the Lamb wave resonator technology with better manufacturability for 6G cmWave wireless communications.[2026-0082]
