Advanced Sensor Research最新文献

Liquid gate-all-around (LGAA) field-effect transistor (FET) biosensors represent advanced material device structures responding electrically to surface potential change and allowing ultra-high sensitivity to biochemical liquids and human bodily fluids. However, the origin and physical working mechanisms for such a type of signals in different complex biochemical solutions remain still many opened questions. Here, noise spectroscopy and impedance methods are applied to study liquid–solid interface properties in LGAA FETs working in adjusted physiological solutions of different pH values. High-quality liquid LGAA Si nanowire (NW) FET biosensors demonstrate the high electronic performance of I–V characteristics in good agreement with modeling data. Impedance spectroscopy measurements allow for analyzing the double-layer capacitances and ion behavior under different pH conditions. Moreover, the noise spectra of the current fluctuations in the biosensors for several solutions are analyzed at different applied liquid-gate and drain-source voltages. The results demonstrate accurate detection of the dynamic ion processes on the nanowire surface. Charge inversion effect is revealed in single-valent ion solutions. Tiny signal characterization results obtained using the LGAA NW FET biosensors provide broader insights into the optimization of sensor parameters for biomedical molecular detection.

Chromogenic and fluorogenic substrates are important for the detection of enzymatic activity. Conjugates of 4-nitrophenol are among the earliest investigated classes of molecules and have been used in diagnostic applications, including those for type-2 diabetes. The detection of 4-nitrophenol under physiological conditions enables real-time monitoring of glucosidase activity. This becomes possible when the resonance structure of 4-nitrophenol is altered, making it distinguishable from its precursor chromogenic substrate. One of the surface-modified silica materials, comprising an acetyl-protected mannoside along with precipitated byproducts such as acyl-urea and urea formed during carbodiimide coupling, induces a unique resonance shift in 4-nitrophenol upon interaction. Raman microscopic analysis can distinguish the phenol-type band at 1330 cm⁻¹ and the quinone-type band at 860 cm⁻¹, thereby enabling monitoring of the α-glucosidase reaction.

Metal halide perovskites (MHPs) are emerging as promising candidates for gas sensing due to their tunable optoelectronic properties, room temperature operation, and scalable fabrication. In this work, hydrogen (H₂) sensing capabilities of methylammonium lead iodide (MAPI) thin films via photoluminescence (PL) spectroscopy is investigated. MAPI films demonstrate a consistent and rapid PL intensity response in a matter of seconds upon exposure to H₂, characterized by an initial increase followed by a decay below baseline, which recovers in ambient air. This reversible behavior is preserved over multiple cycles over an hour, indicating reusability. The magnitude and duration of the PL response vary with H₂ concentration, demonstrating the sensor's ability to detect not only presence but also quantity of gas. Control experiments using encapsulated films confirm specificity to H₂, and X-ray Diffraction (XRD) analysis confirm the interaction does not cause any significant crystallographic changes. Further analysis with thinner films and mixed-halide compositions suggests that both surface and bulk interactions, as well as defect-mediated processes, contribute to sensing. This study establishes MAPI as a viable optical sensor for H₂ gas with fast response, sensitivity to concentration, and potential for low-cost implementation.

Palladium nanoparticle (Pd NP)-based resistive-type hydrogen (H₂) sensors are susceptible to interference from oxygen when detecting H₂. In contrast, capacitive-type sensors emerge as promising candidates for addressing this issue, owing to their unique operating principle. Herein, a capacitive-type H₂ sensor is developed to verify the conception, using Pd NPs as the sensing material and integrating them into a novel 3D interdigital electrode (IDE) structure fabricated on a silicon wafer via microelectromechanical systems (MEMS) technology. Comprehensive characterization of the Pd NPs within the 3D IDEs reveals a strong correlation between sensitivity and Pd NP content, with peak sensitivity (61.94) attained at 20 000 ppm H₂ for ≈0.7 mg of Pd NPs. The sensor demonstrated negligible interference from CH₄, CO₂, and CO, underscoring its exceptional selectivity for H₂. Particularly, variation of oxygen concentration in the background gas shows a minor impact on the sensing performance of the developed capacitive H₂ sensor. Additionally, density functional theory (DFT) calculations provide insight into the volumetric expansion of Pd at different H/Pd ratios, showing a maximum expansion of 13.7% at an H/Pd ratio of 1. This work highlights the potential of capacitive-type sensors for high-performance tracking H₂, paving the way for advanced applications in H₂ monitoring.

Analysing the exhaled breath and its condensate (EBC) can offer a simple, non-invasive way to track physiological states through volatile and non-volatile biomarkers detection. Biosensors, leveraging biological recognition elements, as enzymes, promise selective recognition of these analytes and can overcome the limitations of traditional gas sensors. However, transitioning from liquid to gas-phase sensing presents significant challenges, including enzyme instability, weak signals, and lack of sampling standardization. On the other hand, EBC biosensors, while more compatible with biological elements, face limitations due to the low analyte concentrations and variable sample quality. This perspective looks at the current progress in gas-phase and EBC-based biosensors, highlighting the most promising emerging technologies and key limitations. With the right advances, these tools can facilitate the implementation of fast and non-invasive testing in routine healthcare.

Various animals in nature, particularly insects, are equipped with sensory hair capable of detecting minute fluid forces. Inspired by these biological structures, numerous airflow sensors have been developed using Si-based microelectromechanical systems. However, the complexity of the fabrication process and difficulty in integrating shape-controlled sensing elements remain significant challenges. Laser-induced graphene (LIG) has attracted increasing attention as a promising material for various physical sensors, owing to its high piezoresistive sensitivity and simple fabrication process. Polyimide (PI), which is widely used as a substrate for LIG formation, exhibits thermoplastic properties that enable the straightforward creation of 3D structures. This study proposes a single-axis airflow sensor featuring a vertically standing LIG cantilever. The fabrication process involved only a fiber laser for cutting the PI film, forming the LIG-sensing elements, and folding the cantilever structure. The fabricated sensor measured 25 mm × 25 mm at the base and 10.5 mm high. The fabricated sensor integrated surface-mounted circuits within its base. Wind tunnel experiments demonstrate that the sensor exhibits a quadratic response to wind speeds between −10 and 10 m s⁻¹. This approach offers promising prospects for the development of 3D LIG sensing elements for airflow sensors.

Non-enzymatic high-performance glucose sensors are important due to their stability and low cost. Nickel oxide and its composites with various materials such as multi-walled carbon nanotubes (MWCNTs) have emerged as a platform for non-enzymatic glucose detection at micromolar concentrations. In this article, the reaction mechanism within a MWCNTs/NiO/MWCNTs stacked electrode system used for glucose detection is explored and elucidated. Micro-Raman and -Xray Photoelectron Spectroscopy are used to track the changes associated with the chemical state of the MWCNTs in the composite electrode during the oxidation of glucose molecules. The results show that the presence of MWCNTs provides abundant active sites for the electrochemical reaction. The enhanced electron transfer improves sensor sensitivity as evidenced by distinct redox peaks in the cyclic voltammograms. We conclude that the MWCNTs used herewith provide an ultrahigh surface-area-to-volume ratio for the adsorption of OH⁻ ions from the alkaline medium, which, in turn, facilitates the formation of NiOOH from NiO. The NiOOH formed further acts as an oxidizing agent for glucose molecules, altering them to gluconolactone via a chemical reaction that produces hydrogen peroxide while regenerating NiO. The detailed understanding of the reaction mechanism underscores the significant role of MWCNTs in enhancing the efficiency and sensitivity of non-enzymatic glucose sensors.

Recyclable Printed Thermocouples

In article 2400182, Rui Xu, Denys Makarov, and co-workers develop recyclable printed thermocouples featuring eco-friendly design as well as low cost and scalable processing. Magnetic flakes and re-dissolvable polymers enable seamless and efficient magnet-assisted recycling, preserving performance for sustainable large-scale manufacturing.

FKBP12, a peptidyl-prolyl isomerase implicated in cancer, neurodegenerative diseases, and post-transplant anti-rejection mechanisms, represents a critical biomarker for early diagnosis and monitoring. Here, a novel diagnostic nanoplatform is presented for the detection of FKBP12 at nanomolar to picomolar concentrations in biological fluids. The platform integrates a gold-coated Quartz Crystal Microbalance (QCM) functionalized with a synthetic receptor (GPS-SH1) and spacers within a Self-Assembled Monolayer (SAM), enabling direct and label-free detection of FKBP12 in complex biological samples. A careful strategy for the in-silico design and custom synthesis of the receptor is adopted, ensuring optimal binding affinity and additional chemical functionalities for surface chemisorption. The designed nano-architecture demonstrates exceptional sensitivity, with a detection limit in the picomolar range, and high selectivity, as confirmed by minimal interference from abundant serum proteins such as Serum Albumin and Immune Gamma Globulin. Furthermore, the SAM-functionalized sensors exhibit remarkable stability, retaining functionality for up to six months under storage conditions. This work not only advances the field of nanoscale biosensing but also provides a robust, reusable tool for FKBP12 detection, with potential applications in point-of-care diagnostics and personalized medicine. The platform's ability to operate in biologically relevant environments underscores its promise for real-world healthcare applications, including early disease diagnostics.