Microsystems & Nanoengineering最新文献

Glass is one of the most widely used functional materials in various fields, thus developing high-precision, on-demand and low-cost glass microstructuring technologies is essential for both academic and industry. Although numerous technological advancements in the past, it is still a challenge to fabricate microstructures with smooth inclined sidewalls on glass substrates, posing difficulties in fulfilling the advantages of glass material for many emerging applications, including optics and MEMS. In this paper, we establish a novel quasi-anisotropic wet etching strategy that expands the ability of glass micromachining and enables tunable inclined surface fabrication with high quality and low cost. By exploring the competitive effects of the etching induced by interface between glass and the mask layer, the quasi-anisotropic wet etching mechanism is systematically investigated. Through numerical simulations and experiments, the reproducibility and tunability are verified in fabrication of varied types of microstructures such as microprism, micro-pyramids and micro-cones. Furthermore, novel devices including diffusion plates, optical waveguide, VR/AR displays are designed and manufactured, with functions successfully demonstrated. The quasi-anisotropic wet etching strategy proposed in this paper not only offers a new path for precise and high-quality glass micromachining, but also enables significant application potentials in micro-optics, opto-MEMS and other related fields.

Vibration sensors play a crucial role in resource exploration, structural health monitoring, and seismic activity detection. Conventional vibration sensors, primarily including electromagnetic, capacitive, piezoelectric, and fiber optic types, have been predominantly utilized in past vibration detection applications. However, with the development of deep-sea resources, vibration detection in such extreme environments demands sensors with low-frequency response, low noise, and high environmental resilience, requirements which are challenging for conventional sensors to meet. Due to their high sensitivity and low noise in the low-frequency domain, electrochemical vibration sensors have garnered increasing attention in recent years. Concurrently, advances in MEMS technology have driven the development of electrochemical vibration sensors towards cost-effectiveness, miniaturization, and low power consumption. This review summarizes the sensing mechanism models and noise models of electrochemical vibration sensors. It highlights the trends in the development of sensing electrodes, including miniaturization and integration facilitated by MEMS technology, while also outlining representative fabrication processes. Furthermore, the review summarizes key application domains encompassing geophones, hydrophones, and angular acceleration sensing. Finally, it concludes with a discussion of current major challenges and an outlook on future research directions.

Recent advances in microelectromechanical systems (MEMS) resonators have enabled the development of compact devices capable of precise magnetic and electric field sensing. This review focuses on resonant MEMS sensors that employ electrostatic actuation, offering advantages such as low power consumption, fast mechanical response, and CMOS-compatible fabrication. We classify two primary types of resonant MEMS sensors based on their sensing mechanisms, where magnetic field sensors utilize electromagnetic induction and electric field sensors rely on electrostatic induction. For each type, we analyze representative devices in terms of actuation schemes, resonator design strategies, sensitivity enhancement techniques, and directional detection capability. We also address key design considerations and fabrication constraints. The review summarizes current approaches and characteristics of MEMS resonator-based magnetic and electric field sensors with a focus on their structural principles and application contexts. Through this analysis, the review aims to provide insights that support the development of next-generation field sensors for applications in navigation, biomedical diagnostics, vehicle detection, and non-destructive evaluation of electrical systems.

Digital micromirror device-based maskless projection lithography (DMPL) has emerged as a transformative nanopatterning platform, yet faces fundamental challenges in resolving high-density nanostructures due to optical diffraction constraints. The filtering characteristics of the pupil function and the phase modulation caused by defocus lead to pattern distortion and loss of high-frequency information, making it difficult to ensure consistency and distinguishability in dense pattern lithography. Here, we introduce multiple exposures (ME) to DMPL, developing a multiple-exposure without alignment solution to solve the problem of indistinguishable dense pattern exposure. At the same time, we also propose a novel method to maximize the spacing uniformity of the layout decomposition scheme based on the gradient descent algorithm. We further improved the depth of focus by maximizing the uniformity of spacing, achieving decoherence of sub-layouts within the laser field, thereby ensuring the printability of dense patterns. Simulations and experimental results verify that this approach significantly expands the process window and improves lithographic resolution. For one-dimensional dense lines, the minimum resolvable period decreases from 378 nm (half pitch ~ 0.5λ/NA) to 223 nm (half pitch ~ 0.3λ/NA). Furthermore, the metal layer layout of the integrated circuit chip has a minimum gap of 1 DMD pixel (75.6 nm in image plane) is achieved, demonstrating the efficacy of the proposed methods in addressing the challenges posed by dense layouts in DMPL applications. This work provides a paradigm-shifting solution to the persistent "density-fidelity trade-off" in digital nanofabrication, charting new pathways toward next-generation functional meta-devices.

Insect-scale flapping-wing micro aerial vehicles (FWMAVs) possess compact dimensions, exceptional terrain adaptability, and operational stealth, presenting transformative potential for reconnaissance and environmental monitoring applications. However, current insect-scale FWMAVs typically suffer from limited payload capacity, making integrating the necessary electronic components for flight and functionality challenging. This study presents an enhanced structural design for an FWMAV that increases its payload capacity. By adjusting its transmission ratio and wingspan, the size and carrying capacity of the robot can be changed according to the demand. Based on this novel design, we manufactured FWMAVs with a variable wingspan ranging from 28 mm to 45 mm, the robots achieve a lift-to-weight ratio exceeding 2. This represents the insect-scale piezoelectric-driven FWMAV capable of successful takeoff by adjusting only the transmission ratio and wingspan, without altering other components. Notably, the 28 mm configuration is the smallest functional piezoelectric-decoupled FWMAV to achieve sustained lift-off. Additionally, the combined passive damper structure has allowed the robot to maintain stable hover for more than 5 seconds, achieving sustained air stagnation at an insect scale. These advancements provide certain technical support for further promoting the practical application of insect-scale MAVs.

Resonant nanoelectromechanical systems (NEMS) based on two-dimensional (2D) materials exhibit excellent resonance properties such as a large tuning range, ultralow power, and large dynamic range, leading to broad potential applications in sensing and signal processing. However, scalable fabrication of high-performance 2D NEMS arrays, particularly those with individually addressable electronic control, remains challenging and underexplored. Here, we report a mass transfer printing (MTP) method for the fabrication of large-scale electronically-independent molybdenum disulfide (MoS₂) NEMS resonators with regular isolation spacing. MoS₂ is precisely torn at the edges of polymer protrusions by the surface tension of auxiliary liquid, followed by dry-transfer to the pre-patterned substrate with microtrenches and electrodes. The MTP technique avoids lithographic processes that could lead to collapsing or failure of suspended 2D materials while obtaining electronically independent devices. Characterization of 84 monolayer MoS₂ NEMS resonators demonstrates maintained material quality after transfer, structural integrity, highly tunable resonance frequencies in very-high-frequency (VHF) band, consistent tuning trend of quality (Q) factors, and significant signal-to-noise ratios (SNRs). Independent AC voltage excitation and DC voltage sweeping on different resonators confirm individual electronic control without crosstalk even for neighboring resonators. Furthermore, we design and experimentally demonstrate a functional decimal-to-binary converter building block using adjacent, electrically isolated resonators on a single chip, using gate voltage as input and amplitude at the specific frequency as output. The MTP-fabricated array of independently-addressable MoS₂ resonators advances the large-scale integration of 2D NEMS devices, offering a straightforward and promising pathway for a plethora of applications built upon such device platform.

Proximal Sound Printing (PSP) is a new class of additive manufacturing (AM) processes where on-demand polymerization occurs through ultrasound waves interacting with printing material right at the proximity of the acoustic aperture by inducing cavitation. Despite recent developments in sound-based AM techniques, inherent practical limitations still remain, such as low resolution and repeatability, as well as the inability to print multi-material structures. PSP overcomes these limitations, enhancing resolution tenfold, reducing printing power fourfold, and decreasing maximum acoustic streaming velocity 1600 times compared to common sound-based printing methods, enhancing repeatability and resolution. PSP offers greater versatility than existing methods in modulating feature size through printing aperture tuning. This capability is particularly valuable for fabricating microsystems, where high-resolution patterning and material integrity are essential. Furthermore, PSP enables the direct printing of heat-curing materials such as polydimethylsiloxane (PDMS), a widely used thermoset in microfluidics and soft lithography, without altering its native formulation. The PSP process is explored through sonochemiluminescence experiments and high-speed imaging and demonstrated by the successful printing of multi-material composite structures and functional microfluidic devices. Overall, PSP establishes a practical, high-resolution approach for sound-driven additive manufacturing.

Thermal scanning probe lithography (t-SPL) is a high-resolution nanopatterning technique that employs a heated probe for precise, maskless patterning. Polypropylene carbonate (PPC) has emerged as a promising resist material for t-SPL due to its favorable thermal decomposition behavior. In this study, we investigate the use of PPC as a thermal resist in t-SPL, leveraging its chain unzipping and random scission mechanisms to achieve controlled material removal. The effects of various parameters on the patterning of PPC films, such as temperature, tip height, and force pulse, are systematically examined. Upon exposure to the heated tip, PPC undergoes localized sublimation at the contact area, enabling nanopatterning with the lateral resolution down to 50 nm and the vertical resolution down to sub-nanometer. This approach achieves stepped cyclic and sinusoidal grayscale patterns with controllable depth and size. Furthermore, we demonstrate grayscale pattern transfer by etching the PPC patterns into dielectric layers using optimized dry etching processes. This approach offers precise depth control and shows strong potential for applications in photonic and nano-electronic device fabrication.

Metal oxide semiconductor gas sensors exhibit significant advantages in gas detection due to their high sensitivity and low cost. However, challenges such as poor selectivity and insufficient stability remain critical scientific issues. In this study, tin dioxide nanomaterials with a unique structure were successfully synthesized using ZIF-8 as a template. Further modification with gold-decorated reduced graphene oxide yielded a nanocomposite that demonstrated rapid response, high sensitivity, and excellent selectivity for low-concentration ethylene detection. The crystal structure, morphology, elemental composition, and pore size distribution of the materials were systematically characterized using XRD, FESEM, EDS, UV-Vis spectroscopy, and N₂ adsorption-desorption analysis. Gas sensing tests revealed that the sensor exhibited a response value of 5.35 to 20 ppm C₂H₄ at an optimal operating temperature of 280 °C, with response and recovery times of 14 s and 17 s, respectively. The selectivity ratio for ethylene over the second most sensitive gas was 3.26, highlighting its superior specificity. Additionally, the sensor demonstrated good stability and repeatability, providing a cost-effective solution for real-time ethylene monitoring in humid environments.

Conventional diabetes management requires frequent invasive procedures such as finger-prick blood sampling and subcutaneous injections to coordinate glucose monitoring and medication. Here, we propose a novel, flexible, wearable, battery-free skin patch that synchronizes painless glucose monitoring and regulation capabilities with smartphone-mediated wireless control. This patch integrates bendable fluorescent hydrogel microneedles for minimally invasive glucose monitoring (50 to 450 mg/dL range) and thermoresponsive microneedles for metformin delivery. In diabetic mouse models, it accurately tracked interstitial glucose levels and, upon hyperglycemia detection, reduced blood glucose within 1 h (effects lasting 5-6 h). This system provides glucose monitoring with wireless data transmission and precise drug administration while eliminating pain, infection risk, and high costs. Its lightweight, disposable design offers a practical solution for improved diabetes care.