Micro and Nano Systems Letters最新文献

Heavy metal ions (HMIs), such as mercury (Hg), lead (Pb), cadmium (Cd), arsenic (As), and chromium (Cr), are a serious environmental issue due to their toxicity, bioaccumulation, and long-term persistence, making it necessary to develop sensitive and selective detection technologies. Laboratory-based methods, such as atomic absorption spectroscopy, provide high accuracy, but their point-of-need deployment is limited by their reliance on large equipment and complicated sample preparation. This review highlights the critical role of nanomaterial in sensing platforms in overcoming these limitations and advancements across electrochemical and optical detection techniques. The integration of nanomaterials-including carbon-based, metallic-based, silicon-based, and quantum dots-is shown to significantly enhance sensor performance through increased surface area, electron transfer efficiency, and plasmonic effects. Despite this progress, challenges such as matrix interference, ensuring signal reproducibility, and developing scalable fabrication methods remain. Future research will focus on developing hybrid, multiplexed, and antifouling sensor architectures integrated with digital technologies like the Internet of Things (IoT) to realize next-generation, ultra-sensitive HMIs monitoring platforms.

Laser micromanufacturing is an emerging technique that holds significant implications in a variety of sectors, including biomedical engineering, additive manufacturing, sensors, industrial manufacturing, and microfabrication technologies. The key advantage is the precision as well as efficiency it provides when creating micro and nanostructures, which are becoming more and more important for modern-day applications. As laser microfabrication enables maskless processing, it lowers setup times and costs. It offers an easier alternative to fabricate complicated geometries and conduct rapid prototyping compared to conventional photolithography techniques. Several research works have been reported in this field in the last two decades. However, a major limitation of many of these research works is the fact that they use expensive laser sources such as ultrafast femtosecond lasers. Though femtosecond lasers provide several advantages, it is often not a cost effective method for micromanufacturing. In contrast, low power laser micromanufacturing platforms offer several economic advantages from an industrial point of view such as minimized capital investment, low maintenance costs, and sustainable production due to reduced energy consumption. In this review, we specifically examine cost effective, low power laser micromanufacturing techniques, recent advancements in this field, and future perspectives.

We propose a quantitative metric, the Index of Vibration Influence (IVI), to assess how external random vibrations affect resonant MEMS scanning mirrors that embed a mirror-angle sensor. The setup excites the mirror with PSD-specified random profiles while the mirror is driven near its resonant frequency. The IVI_o, which quantifies vibration‑induced scan‑angle perturbations, is defined at the operating frequency (f_o), as the ratio of the mirror-angle spectra influenced by external vibration to those without random vibration. We validate the linearity error of the embedded sensor as small as 1.25% compared with an external PSM. Using the validated sensor, IVI_o was evaluated at − 45 dB, corresponding to 0.17° angle perturbations at 30.18° OSA, when random vibration was applied at an acceleration level 30% higher in RMS than the IEC 62,498‑3 requirement.

Per- and polyfluoroalkyl substances (PFAS) are persistent organic pollutants whose remarkable chemical stability and bioaccumulative nature pose significant environmental and health concerns. Conventional analytical techniques such as liquid and gas chromatography–mass spectrometry (LC-MS and GC-MS) offer excellent sensitivity and specificity but remain costly, labor-intensive, and unsuitable for rapid field deployment. Surface-enhanced Raman spectroscopy (SERS) has recently emerged as a promising micro/nano-enabled technology for real-time, label-free, and ultrasensitive detection of PFAS in aqueous systems. This mini-review provides a critical overview of current advances in nanostructured SERS platforms, emphasizing the mechanisms of PFAS–surface interactions, rational design of metallic and hybrid substrates, and progress toward miniaturized and microfluidic detection schemes. Persistent challenges, including limited adsorption affinity, spectral interference, and substrate reproducibility, are analyzed alongside emerging strategies such as surface functionalization, hierarchical nano-structuring, and data-driven spectral interpretation. Finally, future perspectives highlight the integration of SERS with machine learning and scalable fabrication to enable portable, field-deployable environmental sensors. Therefore, the review underscores the potential of SERS as a next-generation analytical tool for sustainable PFAS monitoring and environmental protection.

This paper demonstrates a simulation-based analysis of highly sensitive gas sensor design to detect the Chloroform gas based on an advanced Gate All Around Junctionless MOSFET (GAA-JLMOS). In this design, traditional polysilicon gate is replaced with Iridium-Rhodium/Palladium nano-composite (Ir-Rh/Pd) which is responsible for a linear shift in gate work-function in presence of chloroform gas. The work-function modification results into the changes in drain current (I_d) and threshold voltage (V_th), showing a reliable detection from no gas to 50 ppm CHCl₃concentrations by MOS sensor. Additionally, the subthreshold swing optimization leads to faster switching and response times. The simulation results showa significant improvement in the sensitivity of proposed sensor compared to conventional MOS based designs. This manuscript proposes better selectivity towards the detection of chloroform vapors compared to the existing MOS based gas sensors. The simulation results meet a 2x times increase in threshold voltage and 100x times reduction in the leakage current from no gas to 50 ppm concentration of CHCl₃. The proposed GAA-JLMOS shows high sensitivity, low leakage current, and enhanced scalability, providing a possible pathway toward next-generation nanoscale gas sensors. An ATLAS 3D TCAD simulator is used for the sensor design and simulations.

Water-based triboelectric nanogenerators (TENGs) have recently attracted attention as promising solutions for distributed micro energy harvesting. These devices provide a way to provide sustainable power to low-power electronics and self-driving sensors by converting the kinetic energy of water droplets, flowing water, and sea waves into electricity through contact electrification and electrostatic induction. This review provides a comprehensive overview of recent progress focused on the working mechanisms, structural design, and performance improvements in various water environments of water-based TENGs. Key mechanisms such as bulk-effect water droplet-based electricity generation and electrode ground capacitance are summarized. Finally, we discuss current challenges and prospects for scalable and durable self-driving systems, along with their potential applications in environmental monitoring, wearable electronics, and marine sensing.

Low-cost preparation of nanostructured materials is one of the important factors for the commercialization of sensors. This study reports the sustainable and low-cost synthesis of pure SnO₂ and SnO₂-CuO nanostructures using a domestic microwave annealing approach. The material obtained was structurally examined using X-ray diffraction and a scanning electron microscope. The pure SnO₂ and SnO₂-CuO inks were deposited over laser-induced graphene interdigitated electrodes. Towards the volatile organic compounds, the pure SnO₂ and SnO₂-CuO went through ethanol sensing. The SnO₂-CuO-based sensor demonstrated strong response and selectivity for detecting ethanol at room temperature with a response of 11%, a response time of 53 s, and a recovery time of 64 s at 100 ppm of ethanol. The high response and selectivity of the sensor towards ethanol make it ideal for continuous tracking in both environmental and industrial settings.

This paper presents the design and performance evaluation of an optical energy harvesting system for a wireless actuated micro-electro-mechanical system (MEMS) The latter consists of an antagonistic double beam and two active shape memory alloy elements (SMA: (:{3*1*0.1:mm}^{3})) responsible for actuating the beams among the two stable positions, when heated by a laser diode. The research focuses on harvesting the unused laser energy using a vertical multi-junction photovoltaic cell (PV cell: (:{3*3*0.4:mm}^{3})). To extract the maximum efficiency, the energy harvesting system is optimized by homogenizing the laser beam using an N-BK7 light pipe homogenizing rod. The uniformity test is validated experimentally by using an optoelectronic system able to move along the output and measure the power on different zone of the surface; resulting a percentage of uniformity ( across a surface of (:3.5*3:{mm}^{2}), with a standard deviation of ± 3%. The Current/Voltage (IV) curve of the PV cell is extracted under direct illumination of irradiance of 0.93 (:{W/cm}^{2}), resulting a maximum power of 25.2 mW with a fill factor of 84%. To enhance energy utilization, a MEMS active mirror is being introduced to the system to steer the pseudo-uniform laser rays onto the SMA elements alternately (period = 5 s). The IV curve of the PV cell for each position is extracted resulting a fill factor of 92.3% for position 1 and 93% for position 2. While cycling, the unused energy from the laser is being captured by the PV cell resulting to harvest (:37.4:mJ) for the first cycle. This cycle is repeated 50 times to calculate the cumulative amount of energy harvested then 300 times to charge 90% of the capacity of a solid-state thin film micro-battery with initial state of charge (SOC) of 48%. Finally, the decrease in the efficiency of the PV cell is calculated after introducing the bistable beams resulting in a drop of 5%. This research introduces an advances approach to energy harvesting for MEMS, offering valuable insights into efficiency optimization and potential applications in autonomous systems.

This paper examines the feasibility of using an AC Joule-heated stainless-steel (SS304) suspended microtube as a combined heater/thermometer to identify the thermal conductivity (:{k}_{l}) and volumetric heat capacity (:{left(rho:{c}_{p}right)}_{l}) of nanoliter-scale liquids, including electrically conducting liquid metals. The analysis builds on the 3ω technique, wherein a sinusoidal drive at frequency f produces temperature oscillations at 2ω and a third-harmonic voltage V_3ω carrying the sample’s thermal signature. A first-order axial heat-flow model is formulated for a circular microtube and extended to treat two electrical boundary conditions inside the tube: (A) a conformal inner insulator (no electrical shunting through the liquid) and (B) direct electrical contact to a conductive liquid, which creates a parallel electrical path and modifies both Joule power and effective temperature coefficient of resistance. This study outlines an identification workflow for {(:{k}_{l}), (:{left(rho:{c}_{p}right)}_{l})} from the complex V_3ω(f), discuss implementation constraints, and present representative spectra computed for real liquids and for a high-k liquid metal (NaK). The results indicate that, after calibration, the insulated case can recover {(:{k}_{l}), (:{left(rho:{c}_{p}right)}_{l})} from frequency response alone, and that even when the liquid is electrically conducting, the degradation in signal can be modeled and corrected if the parallel conduction is characterized.

Microphysiological systems (MPS) have shown their capabilities in mimicking in vivo-like structural and functional complexity and are seeing significant increase in their utilization in the field of drug discovery and toxicology. However, the major time-consuming steps in the fabrication, utilization, and analyses of MPS devices limit the throughput for broader adoption. Here, we advanced the previously developed two-chamber MPS model of the female reproductive tracts from a single unit chip to an array type chip that is compatible with multi-channel pipettor or automated liquid handling robot for rapid and more efficient operation. To enable this array model, a new microfabrication method was developed, incorporating a microplate holder, bonding guide plate, and soft lithography cassette to minimize device-to-device variation. To validate its compatibility with multi-channel pipettors in chemical toxicity testing, cadmium, a chemical previously shown to elicit cytotoxicity in the two-chamber feto-maternal interface MPS model, was utilized to demonstrate highly uniform cell loading (variance < 100 cells/mm²) and consistent dose-dependent cytotoxic response. Additionally, a liquid handling robotic system was also utilized, with no operational errors such as air bubble introduction (zero bubbles out of 100 devices) during cell/chemical loading process, and no unintended cytotoxic effects (> 97% viability). These results highlight that this automation-compatible array type MPS device can provide highly consistent cell culture performance and significantly reduced chip-to-chip and operation-to-operation variations, overcoming the limitations of typical MPS devices.