Microsystems & Nanoengineering最新文献

Wearable sensors for continuous physiological monitoring during intense exercise face significant challenges, including motion artifacts and skin discomfort. Conductive hydrogels offer a promising solution due to their skin-like flexibility and excellent electrical conductivity, yet their application in extreme conditions like marathon running remains challenges. Here, we develop a MXene-based dual-network hydrogel composed of polyvinyl alcohol (PVA) and tempo-oxidized cellulose nanofibers (TOCNF) crosslinked with MXene nanosheets and borax. This hydrogel exhibits exceptional environmental stability (35 days at 4 °C and 30% relative humidity) and strain sensitivity (gauge factor of 7.79 at 800% strain), while MXene integration provides outstanding antibacterial properties (>99% inhibition). As a proof of concept, under simulated marathon conditions (38°C, 52% relative humidity), the sensor maintains stable performance for 6 h, demonstrating reliable heart rate and respiration monitoring. These capabilities are crucial for identifying early signs of cardiorespiratory abnormalities during endurance sports. Our work presents a robust strategy for developing wearable hydrogel sensors with long-term reliability in extreme environments, offering significant potential for sports medicine, exercise physiology, and continuous health monitoring applications.

Flexible and wearable devices require high-performance pressure sensors for human motion monitoring, but conventional sensors have limited deformability and complex fabrication. To overcome these issues, a composite structure incorporating conductive nanomaterials and a deformable elastomer has been proposed. However, an inherently weak adhesion between the elastomer and nanomaterials remains a practical challenge. To address this, we show a porous polymer sponge coated with Ti₃C₂T_x MXene as an ultra-sensitive pressure sensor. The sensor is fabricated by creating a deformable elastomer sponge using a sugar template, followed by a simple dip-coating process to apply MXene nanosheets. The elastomer surface is chemically treated using surfactants to enhance the surface energy and induce electrostatic forces, thereby improving adhesion between the elastomer and MXene while maintaining the intrinsic mechanical properties of the elastomer. This stable MXene-based network ensures high sensitivity across a broad pressure range. The sensor's low stiffness and porous structure enable rapid response to subtle pressures like breathing and gentle touch, as well as larger forces like arm bending and foot pressure. When integrated into a human-machine interface for the walking assistive device, the pressure sensors enable active control of the exoskeleton, facilitating easier joint motion for rehabilitation.

Two-dimensional (2D) materials are intensively studied as promising materials for gas sensors owing to their large surface area and low working temperature. In this work, we report the synthesis of a layered SnS₂ single crystal by a chemical vapor deposition (CVD) approach for NO₂ sensing. By tuning the growth temperature, high-quality crystals with a lateral size over 3 mm are obtained in 30 min. The 2D SnS₂ sensor with optimized thickness (~15 nm) shows a low detection limit (2 ppb), a fast recovery time (66 s/1 ppm), and a high response (~4702% @ 1 ppm NO₂) at room temperature (RT) under UV illumination. An in-situ Kelvin probe force microscope is employed to reveal the high selectivity of SnS₂ through qualitative and semi-quantitative analysis of charge transfer behavior, including the directions and amount of charge transfer, upon exposure to different gases. In-situ Raman and first-principles density functional theory calculations further confirm the sensing mechanism toward NO₂. Both experimental and theoretical results suggest that 2D SnS₂ holds promising potential as an RT NO₂ sensing material.

Precise intraoperative delineation of deep glioma margins remains challenging, as existing imaging modalities are limited by brain shift, poor penetration depth, or low spatial resolution, thus compromising surgical accuracy. Electrophysiological differences between tumor and normal tissues offer potential biomarkers, but lack high-resolution in vivo validation. We developed NeuroDepth, a tungsten-based multi-channel microelectrode array. With an implantation depth of up to 9 cm and 8 recording sites, the probe provides whole-brain accessibility. Its 15 µm diameter recording sites enable single-cell spatial resolution, while a 30 kHz sampling rate ensures high temporal fidelity for real-time signal acquisition. In this study, NeuroDepth was applied intraoperatively for the first time to monitor deep human glioma tissue. Spatial electrophysiological heterogeneity and longitudinal path-dependent variations revealed electrophysiological markers distinguishing tumor versus normal tissues. Compared with normal cortical surface recordings, glioma regions exhibited elevated neuronal firing rates, altered spike morphologies, and enhanced local field potential synchrony. Neuronal avalanche analysis revealed aberrant criticality within glioma tissue, suggesting unique dynamic network properties useful for boundary detection. A longitudinal recording along the cortex-white matter-tumor trajectory identified a characteristic "rebound" in neuronal activity upon entering the tumor, providing a clear demarcation signature. NeuroDepth demonstrates a new paradigm for intraoperative guidance, leveraging real-time electrophysiological detection to map deep tumor margins at a quantifiable single-cell resolution. It emerges as a promising tool to enhance resection accuracy while protecting functional brain areas.

Ultrafast temperature field detection and identification is crucial for applications ranging from environmental sensing and biomedical monitoring to thermal management in advanced energy systems. Conventional temperature sensors-comprising discrete sensing arrays, data storage units, and external processors-suffer from high latency due to slow sensor response, repeated analog-to-digital conversions, and extensive data transmission inherent to von Neumann architectures. Here, we report a diamond array-based quantum sensor that integrates temperature sensing and real-time processing within a unified in-sensor computing (ISC) architecture. Exploiting the strong linear correlation between temperature and the zero-field splitting of nitrogen-vacancy (NV) color center centers in diamond, we realize a fixed-frequency temperature sensor with ultrafast response and tunable responsivity, enabled by multi-parameter microwave modulate. Matrix-vector multiplication of temperature intensity and responsivity, combined with Kirchhoff's current summation, enables direct execution of neural-network-style computations on sensed data. The proposed system achieves a single-shot detection and identification latency of just 196.8 μs, as experimentally validated. This work demonstrates a scalable ISC-enabled quantum sensing paradigm, offering a promising route toward high-speed, low-power intelligent temperature field detection.

This paper demonstrated the feasibility of utilizing miniaturized piezoelectric micromachined ultrasonic transducer (PMUT) to form a symmetric V-shaped acoustic beam pattern, which enables the ability to synchronously transmit bidirectional ultrasonic signals, and offers a promising technology to address the frame rate limitations in traditional ultrasonic flowmeters based on time-of-flight (ToF). In contrast to the previous two-step flow rate monitoring scheme, where paired ultrasonic transducers are used as transmitter and receiver alternately to obtain the upstream and downstream ultrasound propagation time sequentially, we proposed one-step mid-air flow rate measurement with a remarkable frame rate through the V-shaped bidirectional beam generated by a 3.6 mm × 3.6 mm 5-channel ~250 kHz PZT PMUT phased array. By utilizing the grating lobe produced through optimized array pitch design and sequential control, this 5-channel PMUT array breaks the conventional design limitations typically associated with grating lobes, and generates the V-shaped beam with dual main lobes measured at 27° and 153°, enabling 1000 times of upstream and downstream ToF measurements in 1 s. Furthermore, installation geometry optimization was proposed to enhance the ToF resolution and adaptation to various pipe circumstances, where flow rate measurements in conventional straight pipe and optimized zigzag-shaped pipe with 150 mm sufficient ultrasound propagation length were investigated. The experiment results demonstrated the superior flow rate monitoring performance of our device and system, where large-range (0.5-35 L·min^-1 or 0.045-3.177 m·s^-1, airflow) and high-resolution (185 ns/(L·min^-1) or 2032 ns/(m·s^-1)) flow metering with significant linearity (0.997) was successfully obtained, revealing great potential in advanced flow monitoring application scenarios.

This paper reports the first microscale gas chromatography (μGC) system in which all fluidic components are monolithically integrated into a single 15 × 15 mm² chip, including three Knudsen pumps, a preconcentrator, a separation column, and a capacitive detector. Knudsen pumps utilize thermal transpiration along narrow channels to induce gas flow, providing a compact, motionless solution that enables monolithic integration with high reliability and a long operational lifetime. The flow switching within the system is provided by a unique arrangement of multiple Knudsen pumps that eliminates the need for valves. To realize monolithic integration, the preconcentrator, separation column, and detector are arranged in a planar layout and are designed to be microfabricated using a common fabrication process. Methods to provide heat dissipation and thermal isolation are incorporated. In the experimental evaluation, the fabricated μGC system was operated to analyze the headspace of chemical mixtures, including alkenes, glycol ethers, aromatics, and mercaptans. The results showed a quantification accuracy of ±8.5% for the individual species within the mixtures, which is suitable for specific process monitoring applications in the chemical industry where concentrations of select target species and byproducts must be assessed continuously. The monolithic integration of gas pumps into a μGC system has not been previously reported and is an important step toward further miniaturization of μGC systems.

The emergence of wearable devices capable of continuous biomarker monitoring has significantly transformed the traditional landscape of healthcare, offering real-time insights into physiological changes, enabling early detection of disease, and facilitating individualized therapeutic. Nucleic acid aptamers, as a highly sensitive biorecognition elements with programmable properties, provide an innovative solution for building a new generation of continuous monitoring system. This review presents recent developments in aptamers-based wearable electrochemical sensors for continuous monitoring of biomarkers. Firstly, the core advantages of aptamers in continuous monitoring are summarized, including unique reversible binding properties, excellent biostability and engineerable modification ability, which make them ideal recognition elements for building real-time biosensing interfaces. Secondly, this review provides insights into the design principles of aptamers-based electrochemical sensors, including the characterization of aptamers, the immobilization methods on the electrode surface and the sensing strategies of sensors. Besides, this review highlights recent research advances in the field, focusing on the design of different types of sensors as well as their applications. Specifically, according to the difference target acquisition methods, the type of sensors is classified into non-invasive sensors, which involve monitoring biomarkers present in accessible biofluids such as sweat, saliva and wound exudate, and low-invasive sensors utilizing microneedle patch technology to sample biomarkers within interstitial fluids. Finally, this review introduces the challenges and discuss potential solutions for future development of aptamers-based wearable biosensors, including how to achieve effective biomarkers detection, ensure reversible binding response and ensure long-term stability, etc. This review provides useful reference for the development of aptamers-based electrochemical continuous monitoring technology in healthcare applications.

Flexible photodetectors with wavelength-selective response are essential for next-generation wearable and bio-integrated optoelectronics. However, conventional devices typically rely on external filters or complex structures, limiting the flexibility, integration, and broadband applications. Here, we present a gate-tunable flexible photodetector based on asymmetric van der Waals heterostructures composed of graphene, Molybdenum disulfide and single-walled carbon nanotubes. The asymmetric design induces a built-in electric field, effectively suppressing dark current and enabling dynamic modulation of spectral responsivity via gate voltage. As a result, the device achieves switchable photoresponse peaks at 450 nm and 635 nm, demonstrating a high responsivity of up to 40.3 A/W and a specific detectivity of 1.3 × 10¹¹ Jones. Furthermore, the device maintains robust performance under mechanical deformation and gate voltages. This work offers a scalable approach to realize intrinsically wavelength-selective, high-performance photodetectors on flexible substrates, providing new opportunities for integrated, broadband, and flexible optoelectronic applications.

Three-dimensional in vitro tumor models are increasingly recognized for their value in preclinical oncology, offering enhanced physiological relevance compared to traditional two-dimensional cultures. These systems improve the reliability of drug response assessment and hold potential for advancing patient-specific treatment strategies. In this work, we introduce the Spheromatrix, a paper-based platform designed to support spheroid formation, long-term preservation, and parallelized drug evaluation. This scalable system maintains the viability, proliferation, and metabolic activity of tumor spheroids across a variety of cancer cell lines, including U87 glioblastoma. Importantly, it supports cryopreservation and subsequent re-culture, potentially enabling the generation of pre-formed, ready-to-use 3D tumor models. Drug testing on U87 spheroids revealed consistent cytotoxic effects of cisplatin and temozolomide (TMZ), both as single agents and in combination, before and after cryostorage. Combined treatment amplified cytotoxic outcomes, indicating a potentiating effect of cisplatin on TMZ-induced cell death. These results position the Spheromatrix as a practical and versatile platform for building 3D tumor model biobanks and addressing critical gaps in current model accessibility and reuse.