Microsystems & Nanoengineering最新文献

Accurate detection of arterial pulse waves is crucial for wearable warning systems but faces challenges under non-close contact or pre-stress. Here, an interfacial engineered triboelectric sensor (IETS) has been proposed to improve the detection accuracy of pulse waves. It consists of a stress-transferring sensor-skin interface with piezo-frustums array and a gradient triboelectric interface with mountain-like microstructures. The mountain-like microstructures provide stress concentration points even under a pre-stress of 10 kPa with capturing all details of the pulse waves. Additionally, the incorporation of piezo-frustums array at the sensor-skin interface not only facilitates stress transfer but also generates piezoelectric charges. Such mechano-electric coupling effect endows IETS with a high sensitivity of 4.28 V/kPa. Integrated with machine learning, a wearable system based on IETS allows for drivers' health and fatigue assessment via pulse wave analysis, offering an effective approach to prevent road accidents caused by sudden cardiovascular diseases and fatigue driving.

This work investigates the synergic effect of thermal tuning and mode-coupling on frequency stability in a dual-mode micromechanical resonator. Under dynamic input excitation, the signal in one mode induces the frequency shift of the other mode due to the self-heating and mode-coupling effects. We propose a method to stabilize frequency of the dual-mode resonator under dynamic piezoelectric excitation. The method leverages an on-chip micro-oven to thermally tune the resonator at different temperature coefficients of frequency (TCF) points, enabling the control of self-heating and mode-coupling induced resonant frequency shifts. In our experiment, the resonator is maintained at an appropriately selected TCF point, where the frequency shift caused by mode-coupling can be compensated by the self-heating effect. These findings provide valuable insights into the thermal and nonlinear dynamics of dual-mode resonators and offer a promising strategy for designing high-performance micromechanical resonators in timing and sensing applications.

Insect-scale robots can access extremely confined spaces, demonstrating significant application potential in fields such as disaster relief and exploration within confined environments. Currently, the integrated fabrication and formation are still a challenge for insect-scale piezoelectric robots. In this study, we propose a 1.2 g novel parallel-legged insect-scale origami robot named PLioBot featuring an integrated origami mechanism. This integrated origami mechanism encompasses all the actuators and structures integral to the PLioBot's composition and can be readily fabricated through an improved lamination process. The PLioBot is capable of forward, backward, and turning locomotion, achieving a maximum velocity of 44.6 cm/s (17.84 body length/s) at 60 Hz. It demonstrates adaptability to traverse various surfaces and can successfully climb slopes up to 12°. The robot is able to navigate through confined spaces such as tunnels and L-shaped bends while carrying a payload of 1.4 g. Equipped with hemispherical foot mats, the PLioBot demonstrates enhanced mobility across various complex environments, including grasslands, sandy terrains, and stone surfaces. It is capable of submerged locomotion along the bottom of a fishbowl, as well as swimming on the water surface using the flipper attachment. The PLioBot, along with its integrated origami mechanism and the enhanced lamination process, offers a novel approach for the design and assembly-free fabrication of insect-scale micro robots.

Humanoid robots and human-machine interaction technologies are essential for perceiving and manipulating millimeter-scale objects with irregular surfaces in extreme environments, such as outer space, radioactive zones, and hazardous sites with explosive ordnance, where human access is restricted. A vision-based perception approach provides spatial and positional information about objects but relying solely on it for robot manipulation poses challenges due to limitations in detectable object size, as well as sensitivity to external factors such as focusing issues, occlusion, and lighting conditions. In contrast, tactile perception offers valuable information about aspects that are difficult to discern visually, including an object's shape, surface characteristics, and the forces involved during contact. This study presents a complementary visual localization and tactile mapping framework that allows robots to effectively perceive small objects with irregular surfaces in visually restricted environments. The proposed method draws inspiration from the sequential vision-tactile sensory processing observed in humans when handling small objects with irregular surfaces. It employs an RGB-Depth camera for visual perception and a soft pressure sensor array, made using inkjet printing, for tactile perception. We demonstrate the feasibility of implementing a sensory substitution to detect the size and location of objects through visual perception, as well as identify object surfaces and reconstruct their three-dimensional profiles using tactile scanning, particularly in environments where visual information is limited. This study provides a technological foundation for enhancing the autonomy and adaptability of humanoid robots in unpredictable and unstructured environments, particularly to support precise robot manipulation in such conditions.

The signature of stochastic resonance is that additional noise surprisingly enhances the signal-to-noise ratio (SNR). A noise-adaptive system that learns to add an optimal amount of noise to trigger stochastic resonance and improve SNR is known as adaptive stochastic resonance. However, the current stochastic resonance mechanism fails when environmental noise exceeds the optimal noise level, as any additional noise merely worsens the SNR. In this case, instead of adding noise, stochastic resonance can be facilitated by adapting the potential energy landscape of the bistable system. Here, we propose a novel approach to enhance SNR in noisy environments, involving a potential adjustable microelectromechanical systems resonator. A periodic signal with an amplitude of 0.28 Vrms is buried in ambient noise, emulated by a white noise signal with amplitude ranging from 0.7 Vrms to 4 Vrms. Experimental results show that when the ambient noise exceeds 1 Vrms, adding additional noise leads to a decline in SNR. However, SNR enhancement induced by stochastic resonance is experimentally demonstrated by tuning the potential well of the resonator. This advancement highlights the feasibility of potential adjustable systems to overcome the limitations of conventional noise adjustable stochastic resonance methods in noisy environments. The proposed mechanism is further applied to detect the frequency of 2.7 nN periodic forces with various waveforms.

The force-to-rebalance (FTR) mode is one of the most widely employed measurement schemes in MEMS Coriolis vibratory gyroscopes due to its high precision and stability. However, phase errors distributed across multiple control loops fundamentally constrain the achievable accuracy and robustness of rate measurement. This paper systematically categorizes the phase errors in both the drive modal and sense modal control loops, distinguishing between those arising in the forward and feedback paths, while excluding feedthrough effects. The influence of these phase errors is comprehensively analyzed across three key control loops: the drive modal control loop, the FTR rate control loop, and the quadrature stiffness correction loop. To address phase errors in the drive modal control loop, a dedicated calibration procedure is proposed for both the feedback and forward paths. The effects of phase errors on amplitude regulation, frequency tracking, and FTR rate measurement are quantitatively examined. For the sense modal control loop, an FTR control architecture incorporating phase error characteristics is established, along with a corresponding calibration procedure. Furthermore, the impact of phase errors on the effectiveness of quadrature stiffness correction and FTR rate measurement is investigated in detail. Finally, a comparative analysis of the sensitivity of system performance to various phase errors is conducted, and the relative influence weights of different error sources are determined. The results provide diagnostic insight into the principal mechanisms by which phase errors affect FTR gyroscope performance and lay a foundation for targeted real-time compensation design.

Microfluidic devices play a crucial role in the widespread application of single-cell analysis, where hydrodynamic focusing stands out due to its simplicity in structure and excellent adaptability to a wide range of flow rates. Owing to the extensive application of soft lithography, polydimethylsiloxane (PDMS) is widely used in the fabrication of microfluidic devices. However, challenges arise under high-throughput conditions, where the elastic deformation of PDMS can cause microchannel expansion, diminishing focusing effect. To address this challenge, this work introduces a three-dimensional (3D) hydrodynamic focusing device with simplified single-layer structure, which is fabricated by the double transfer process, specifically designed for fabricating polyurethane acrylate (PUA) microfluidic devices. Notably, this approach eliminates the time-consuming heating procedures, which significantly enhances manufacturing speed by an order of magnitude compared to the soft lithography process. To evaluate the practical focusing performance of the microfluidic device, optical time-stretch (OTS) microscopy is employed for high-throughput imaging of clinical urine samples. Experimental results demonstrate that as the flow rate increases, the focusing efficiency gradually improves in both vertical and lateral directions. At an averaged velocity of 16.7 m/s, the focusing efficiency reaches 98.4% in the vertical direction and 95.0% in the lateral direction. Thus, the amalgamation of simplicity, efficiency, and adaptability positions this technology as a promising tool in the realm of microfluidics, particularly for applications requiring precise cell focusing in high-throughput scenarios.

Electrohydrodynamic (EHD) printing is an advanced micro/nanoscale additive manufacturing technique. Owing to its high-resolution capability, broad material compatibility, diverse printing modes, and low cost, it has attracted widespread attention. Nevertheless, significant challenges remain in transitioning EHD printing from the laboratory to large-scale industrial production. This paper elucidates the mechanisms of EHD printing and details control methods for high-resolution, controllable micro/nanopattern fabrication, including process-parameter optimization, rheological design of functional inks, and innovations in system architecture. We summarize recent applications in electronic devices, biomedicine, and optical components, and discuss development directions and prospects for industrial adoption.

The detectivity of magnetic tunnel junction (MTJ) sensors cannot be improved further because of the existence of 1/f noise. Micro - electromechanical systems (MEMS) integrated with magnetic flux concentrators (MFCs) can be an effective approach to suppressing 1/f noise for modulating low-frequency magnetic fields. The challenge in fabricating small-sized and low-noise MTJ-MEMS hybrid magnetic sensors is associated with the production of high-performance MFCs. For the preparation of MFCs applicable to MTJ-MEMS hybrid magnetic sensors, in this research, a novel Ta/Ni₇₇Fe₁₄Cu₅Mo₄ laminated structure was adopted to decrease the coercivity of the magnetic film dozens of times. Also, through optimizing the sputtering power, a relative permeability of 3246 was attained. The simulation outcomes demonstrated that the MTJ-MEMS hybrid magnetic sensor which utilized this magnetic film had a modulation efficiency of 65.4%, and it retained a competitive edge among similar magnetic sensors. A sensor prototype was successfully developed with 400-nm- thick MFCs by optimizing the fabrication process, and the MTJ's sensitivity was increased by 2.2 times. In comparison to low-frequency noise, the high-frequency noise of the MTJ showed a reduction in noise power spectral density by a factor of 686. MTJ sensors will be highly competitive candidates in the field of ultra-weak magnetic field detection because of these results.

Gene mutation is one of the core pathogenic factors in numerous major diseases, making the detection of base mismatches resulting from these mutations critically important in both biological and clinical contexts. This study presents a high-performance boron-doped diamond solution-gated field-effect transistor (BDD-SGFET) biosensor, designed with a diamond microwire structure, for the label-free detection of base mismatches associated with EGFR gene mutations. The simulations examining the impact of variations in diamond microwire dimensions on the electrical properties of BDD-SGFET reveal that increasing the microwire width while reducing its length enhances the electrical performance of the device. Utilizing microwave plasma chemical vapor deposition (MPCVD), photolithography, and plasma etching, we successfully fabricated high-performance BDD-SGFETs featuring microwire structures that demonstrate outstanding transconductance, a reduced threshold voltage, and a limit of detection of 10 pM. Notably, the enhanced performance of the fabricated BDD-SGFET enables the successful identification of DNA molecules with two base-pair mismatches. Furthermore, the device exhibits impressive anti-interference capabilities and exceptional stability in complex environments. These findings highlight the significant potential of microscale BDD-SGFETs as rapid, label-free, and robust platforms for point-of-care testing in genetic mutation analysis pertinent to cancer diagnosis.