This study presents the design and implementation of a surface plasmon resonance (SPR) sensor in the Kretschmann configuration, employing a gold film deposited on a flexible polydimethylsiloxane (PDMS) substrate as the SPR chip. The refractive-index sensitivity of the SPR sensor was evaluated with sodium chloride solutions of varying concentrations. Optimizing for both sensitivity and detection accuracy, the incident angle was fixed at 13°. The sensor exhibited a sensitivity of 3385.5 nm/RIU. Remarkably, the sensitivity variation was merely 1% after subjecting the sensor chip to 50 bending cycles in both forward and reverse directions. The sensor’s efficacy was further validated through the detection of alcohol content in three different Chinese Baijiu samples, yielding a maximum relative error of 4.04% and a minimum error of 0.17%. Additionally, the sensor was utilized to study the adsorption behavior of glutathione (GSH) on the gold film under varying pH conditions. The findings revealed optimal immediate adsorption at pH = 12, attributed to the complete deprotonation of mercapto groups, facilitating the formation of Au-S bonds with gold atoms. The best film-forming effect was observed at pH = 7, where the interplay of attractive and repulsive forces among different molecular groups led to the gradual extension of the molecular chain, resulting in a thicker molecular film.

In this paper, we propose a spectrally-resolved titanium dioxide waveguide resonant sensor, modified with a perovskite film. The sensor consists of a prism (N-FK51A), gold (Au), hybrid organic–inorganic halide perovskites, and titanium dioxide layers. The thickness of each layer and the incident angle were optimized based on the Fresnel equations. The refractive index sensitivity of the sensor increased by 32.1

Wearable sensors are pivotal for point-of-care diagnostics, yet their application in extreme conditions is rarely conducted. In this work, we present a wearable pH sensor using tungsten oxide aerogel(TOA)as the sensing material. With the advantages of large specific surface area, high porosity and interconnected network structures, TOA not only provides excellent p H sensing performance but also demonstrates remarkable structural and sensing stability. The potentiometric p H sensor exhibits a high sensitivity(-63.70 mV/pH), a low detectable limit(0.05) and a superior stability(maintained over 50,000 s).Integrated with a Bluetooth module, the wearable sensor achieves non-invasive and real-time p H monitoring on the human skin with minimal deviation(1.91%) compared to the commercial pH meter. More importantly, the anti-impact behaviors of the TOA-based sensing materials and chip, along with the p H wearable sensor on a pig exhibit an outstanding shock-resistance ability, with variations no more than7.17% under an impact of 118.38 k Pa. Therefore, this study shows great promise for the aerogel-based personalized health management in the extreme environment.

Wearable electrochemical sensors, which can track various biomarkers in real-time, is one of the most promising bioanalytical devices in the point of care testing and health management. Sample collection modules, as the important front-end of the sensors, capture and transfer enough sample so as to achieve real-time, precise and accurate detection. Noninvasive and minimally invasive techniques for sample collection are highly desired. However, it is still a key challenge to realize a reliable sample acquisition. Herein, we provide an overview on the progress in the sample collection methods for wearable electrochemical sensors. It covers the conventional and emerging methods/structures including reverse iontophoresis, microneedles, as well as microfluidic chips. The working principle, fabrication materials and manufacturing technologies will be introduced in detail. Finally, the present challenges and the development trend in the future of these approaches are also put forward. image

Glucose detection is of significant importance in providing information to the human health management. However, conventional enzymatic glucose sensors suffer from a limited long-term stability due to the losing activity of the enzymes. In this work, the AuNi bimetallic aerogel with a well-defined nanowire network is synthesized and applied as the sensing nanomaterial in the non-enzymatic glucose detection. The three-dimensional (3D) hierarchical porous structure of the AuNi bimetallic aerogel ensures the high sensitivity of the sensor (40.34 μA mM-1 cm-2). Theoretical investigation unveiled the mechanism of the boosting electrocatalytic activity of the AuNi bimetallic aerogel toward glucose. A better adhesion between the sensing nanomaterial and the screen-printing electrodes (SPEs) is obtained after the introduction of Ni. On the basis of a wide linearity in the range of 0.1-5 mM, an excellent selectivity, an outstanding long-term stability (90 days) as well as the help of the signal processing circuit and an M5stack development board, the as-prepared glucose sensor successfully realizes remote monitoring of the glucose concentration. We speculate that this work is favorable to motivating the technological innovations of the non-enzymatic glucose sensors and intelligent sensing devices.

Sweat wearable sensors enable noninvasive and real-time metabolite monitoring in human health management but lack accuracy and wearable applicability. The rational design of sensing electrode materials will be critical yet challenging. Herein, we report a dual aerogel-based nonenzymatic wearable sensor for the sensitive and selective detection of uric acid (UA) in human sweat. The three-dimensional porous dual-structural aerogels composed of Au nanowires and N-doped graphene nanosheets (noted as N-rGO/Au DAs) provide a large active surface, abundant access to the target, rapid electron transfer pathways, and a high intrinsic activity. Thus, a direct UA electro-oxidation is demonstrated at the N-rGO/Au DAs with a much higher activity than those at the individual gels (i.e., Au and N-rGO). Moreover, the resulting sensing chip displays high performance with a good anti-interfering ability, long-term stability, and excellent flexibility toward the UA detection. With the assistance of a wireless circuit, a wearable sensor is successfully applied in the real-time UA monitoring on human skin. The obtained result is comparable to that evaluated by high-performance liquid chromatography. This dual aerogel-based nonenzymatic biosensing platform not only holds considerable promise for the reliable sweat metabolite monitoring but also opens an avenue for metal-based aerogels as flexible electrodes in wearable sensing.

It is important to monitor the intra-/extracellular concentration of hydrogen peroxide (H 2 O 2 ) in biological processes. However, miniaturized devices that enable portable and accurate H 2 O 2 measurement are still in their infancy because of the difficulty of developing facile sensing strategies and highly integrated sensing devices. In this work, portable H 2 O 2 sensors based on Pt-Ni hydrogels with excellent peroxidase-like and electrocatalytic activities are demonstrated. Thus, simple and sensitive H 2 O 2 sensing is achieved through both colorimetric and electrochemical strategies. The as-fabricated H 2 O 2 sensing chips exhibit favorable performance, with low detection limits (0.030 μM & 0.15 μM), wide linearity ranges (0.10 μM–10.0 mM & 0.50 μM–5.0 mM), outstanding long-term stability (up to 60 days), and excellent selectivity. With the aid of an M5stack development board, portable visual and electrochemical H 2 O 2 sensors are successfully constructed without complicated and expensive equipment or professional operators. When applied to the detection of H 2 O 2 released from HeLa cells, the results obtained by the developed sensors are in good agreement with those from an ultraviolet‒visible spectrophotometer (UV‒vis) (1.97 μM vs. 2.08 μM) and electrochemical station (1.77 μM vs. 1.84 μM).

A group of lead-free (1 − x)(0.65Bi0.5Na0.5TiO3–0.35Sr0.7Bi0.2TiO3)–x[Ba(Zr0.3Ti0.7) O3] [(1 − x)BNT–SBT–xBZT] ternary ceramics is prepared through the traditional solid-phase sintering reaction. The introduction of relaxor dielectric ceramic Ba (Zr0.3Ti0.7)O3 (BZT) can reduce the grain size, form a typical “ferroelectric + relaxor ferroelectric” lead-free system, and refine the hysteresis loops and improve η through site doping. As such, the dielectric anomaly peaks gradually shift to lower temperature and show a diffusion phase transition behavior over a wide temperature range, resulting in an active relaxation with the increase of doping BZT. Remarkably, the high energy density performance (Wrec and η are 1.00 J cm−3 and 87%, respectively) is obtained in this 0.86BNT-SBT-0.14BZT ceramic at relatively low electric field of 80 kV cm−1. This work is an appropriate reference to promote the energy storage performance of BNT-based ceramics by introducing BZT, providing an approach for lead-free dielectric materials.

A group of lead-free (1 − x )(0.65Bi 0.5 Na 0.5 TiO 3 –0.35Sr 0.7 Bi 0.2 TiO 3 )– x [Ba(Zr 0.3 Ti 0.7 ) O 3 ] [(1 − x )BNT–SBT– x BZT] ternary ceramics is prepared through the traditional solid-phase sintering reaction. The introduction of relaxor dielectric ceramic Ba (Zr 0.3 Ti 0.7 )O 3 (BZT) can reduce the grain size, form a typical “ferroelectric + relaxor ferroelectric” lead-free system, and refine the hysteresis loops and improve η through site doping. As such, the dielectric anomaly peaks gradually shift to lower temperature and show a diffusion phase transition behavior over a wide temperature range, resulting in an active relaxation with the increase of doping BZT. Remarkably, the high energy density performance ( W rec and η are 1.00 J cm −3 and 87%, respectively) is obtained in this 0.86BNT-SBT-0.14BZT ceramic at relatively low electric field of 80 kV cm −1 . This work is an appropriate reference to promote the energy storage performance of BNT-based ceramics by introducing BZT, providing an approach for lead-free dielectric materials.

We synthesize a group of three-phase ferroelectric ceramics 0.35(Sr0.7Bi0.2) TiO3–0.65(Bi0.5Na0.5)TiO3–xSr(Mg1/3Nb2/3)O3 (BST–BNT–xSMN) using conventional solid-phase sintering method. When tunning the volume of SMN to 0.01, the ceramic sheet shows homogeneous microcrystal grains and highly dense crystal morphology, which favors a reductive dielectric permittivity (εr) of 2250 and loss of 0.05. Under a high electric field of 100 kV cm−1, the BST–BNT-0.01SMN sample achieves a slender polarization versus electrical field (P–E) loop with saturation and residual polarization of 37.1 µC cm−2 and 3.0 µC cm−2, respectively, corresponding to a high energy density of 1.32 J cm−3 and a large η of 81%. Strikingly, the BST–BNT–xSMN ceramics show the excellent temperature stability below 100 °C, which facilitates energy storage in relaxed ferroelectric ceramics and provides an efficient method for obtaining pulsed power capacitors with excellent energy-recoverable characteristics and high efficiency in BNT-based ceramics. The three-phase ferroelectric ceramics 0.35(Sr0.7Bi0.2)TiO3- 0.65(Bi0.5Na0.5)TiO3-xSr(Mg1/3Nb2/3)O3 (BST- BNT- xSMN) possesses a slender polarization versus electrical field loop with saturation and residual polarization of 37.1 µC cm-2 and 3.0 µC cm-2 respectively at 100 kV cm-1, which corresponds to a high energy density of 1.32 J cm-3 and a large η of 81%.

Polymer piezoelectric materials polyvinylidene fluoride (PVDF) and its copolymers P(VDF-TRFE) and P(VDF-HFP) are typical organic polymer materials with piezoelectric properties. Currently, these materials attract great attention in academic and application area for their good mechanical properties, corrosion resistance, biocompatibility and easy processing. However, compared with the traditional inorganic piezoelectric ceramic materials, the piezoelectric constant of polymer piezoelectric materials is still relatively low, so improving the piezoelectric properties of such polymer piezoelectric materials has become one of the research hotspots at home and abroad. In this paper, the methods of improving the piezoelectric properties by combining PVDF and its copolymers with different functional materials at national and international levels in recent years are summarized, and the advantages and disadvantages of different types of fillers doped with different polymer piezoelectric materials and their development trends are prospected.

A group of 0.65(Bi 0.5 Na 0.5 )TiO 3 -0.35(Sr 0.7+ x + Bi 0.2 )TiO 3 (BNT-S 0.7+ x BT) composite ceramic pellets are synthesized using a traditional solid sintering method, where a tunable x, the changeable volume of Sr, is to tailor energy storage through the adjustments of the A-site stoichiometry in BNT-S 0.7+ x BT. We find that a small excess of Sr 2+ ions will result in an extensively tuning on the crystal grain size and even contribute to the A-site disorder and charge fluctuation of BNT-S 0.7+ x BT. As such, the BNT-S 0.7+ x BT exhibits a minimum average grain size and a highly compact crystal morphology, and thus, BNT-S 0.75 BT ceramic exhibits a high dielectric constant ( ε r ) of about 5100 at 110 °C. Meanwhile, a relatively thin polarization–electric field (P–E) loop with a high maximum polarization of 42 μC/cm 2 and a low remnant electric polarization of 5 μC/cm 2 are obtained in a BNT-S 0.75 BT pellet under 100 kV/cm, corresponding to an energy density of 0.98 J cm −3 and a good η of 70.7%. Attractively, the maximum polarization ( P m ) of BNT-S 0.75 BT ceramic at 25–100 °C hardly decreases, implying excellent temperature stability of polarization performances under high electric field of 100 kV/cm, which favors the energy storage of relaxor ferroelectric ceramics and is valuable to a supercapacitor serving at evaluated high temperature.

In this paper, a temperature-compensated three-dimension vector fiber optic magnetic field sensor based on an elliptical core micro fiber Bragg grating (FBG) has been proposed and experimentally demonstrated. The elliptical core fiber was tapered to form a microfiber, in which a FBG was inscribed. Due to the magnetism-manipulation of the anisotropic aggregation of ferromagnetism nanoparticles around the fiber surface, the effective refractive index of the evanescent field for two orthogonal polarization modes was modulated, and the magnetic field orientation can be detected by interrogating the wavelength interval between two reflection peaks. However, two reflection peaks show the identical response to ambient temperature. Hence the proposed sensor can achieve the measurements of the magnetic field intensity and the orientation simultaneously without the temperature cross-sensitivity. The experimental results show that the magnetic field orientation sensitivity of 15 pm/deg and intensity sensitivity of 81 pm/mT can be achieved, and the maximum standard variation of the temperature cross-sensitivity is only 0.02 nm. The proposed elliptical core micro FBG appears to have potential applications in navigation, vehicle detection, and current sensing.

Temperature cross-sensitivity is a long-standing challenge for most of the in-line fiber optofluidic waveguide biosensors. In this paper, we propose a dual-optofluidic waveguide antiresonant reflecting optical waveguide (ARROW) biosensor for the detection of interferon-gamma (IFN-γ) concentration with temperature compensation. Two Fabry-Perot resonators infiltrated with IFN-γ and NaCl were formed in a hollow core fiber, which generate two resonance dips based on the ARROW model. The optical biosensor for the detection of interferon-gamma (IFN-γ) has been a key research interest in recent years because IFN-γ is an important early biomarker for many serious human diseases. Based on the dual-optofluidic waveguide ARROW biosensor, the IFN-γ concentration can be measured through the modulation of the resonance condition of the ARROW, while the temperature fluctuation can be eliminated due to same thermo-optic coefficients of two infiltration liquids. The experimental results show that the response of the ARROW biosensor can be amplified significantly with the signal-enhanced streptavidin, and the limit of detection of 0.5 ng/ml can be achieved for the IFN-γ concentration. More importantly, the influence of the temperature could be compensated through the referenced resonance dip. The proposed fiber biosensor has a great potential for the real-time detection of IFN-γ concentrations in the fields of health monitoring, cancer prevention, biological engineering, etc.

A thermal convection-based fiber lever sensor is proposed and experimentally demonstrated. Instead of the solid or liquid mass found in a conventional lever sensor, a Co2+-doped microfiber is self-heated with a pump laser as the heat source, generating a symmetrical temperature profile inside a hermetic chamber due to thermal convection. The convection current generated by the temperature gradient remains in the opposite direction to gravity with different tilt angles, due to a natural convection effect acting as a “gas pendulum”. However, the locations of two micro-single mode fibers are asymmetric, corresponding to the central axis of the temperature gradient. Therefore, the tilt angle can be detected by interrogating the wavelength shift of the Michelson interferometer induced by the temperature difference. The experimental results show that a tilt-angle sensitivity of 95 pm/deg can be achieved. The proposed fiber-optic lever sensor possesses large dynamic range, low cost, and high sensitivity.

This work reports a novel optical sensor with automatic sampling system for real-time detection of ammonia nitrogen over a wide concentration range. The sensor is based on reversible color change of the sensing element induced by ammonia gas released from the alkalinized water sample. The sensing element consist of an indicator of bromothymol blue (BTB) loaded in a porous glass membrane. The sensor detects a low concentration of ammonia nitrogen in water by measuring the change in absorbance for a fixed period of time, and detects a high concentration of ammonia nitrogen by recording the time required for the absorbance to reach a given value. The sensor was characterized using a series of aqueous ammonium chloride solutions with different concentrations as the ammonia-nitrogen samples. According to the experimental results, the absorbance at 10 min after the sample injection linearly increases with increasing the ammonia-nitrogen concentration up to 0.5 mg/L. Beyond 0.5 mg/L the time-recording mode was automatically adopted, and the time taken for the absorbance to reach 0.2 was measured to be a power function of concentration. The two measurement modes of the sensor extend its dynamic range and improve the detection accuracy, offering the sensor widespread applications.

The ambient temperature fluctuation is a long-standing challenge for the hot wire anemometer due to the strong cross-talk. Here, a graphene-coated elliptical core micro-fiber Bragg grating has been proposed for the detection of flow rate with the temperature compensation. With the strong interaction between the graphene layers and the heating light, the graphene coat on the surface of the microfiber can be heated, acting as a heater. The flow rate can be measured through the different responses of two orthogonal polarization modes to the refractive index change of the graphene layer induced by the heat transfer. More importantly, due to the identical response of two polarization modes to the ambient temperature, the fiber-optic anemometer could compensate the temperature cross-talk effectively. The experimental results show that the sensitivity of the 0.42 nm/(m/s) for the fiber anemometer can be achieved, and the temperature standard variation is only 0.084 nm with the range from 20°C to 50°C. The proposed fiber-optic anemometer is very attractive in the fields of various industries for the temperature self-compensation detection of gas flow.

The study was aimed to elucidate the molecular mechanism of Farnesyl X receptor (FXR), Bile salt export pump (BSEP) and sodium-taurocholate cotransporting polypeptide (NTCP) in the metabolism of bile acid and cholesterol in hyperlipoidemia rats. Fifty male Wistar rats weighing 140.6 +/- 9.5g were randomly divided into two groups: the control group was given normal diet while the experimental group was given high-fat diet. Body weight was measured on a regular basis and liver weight was measured after sacrifice. Plasma glucose and lipids (total cholesterol, triglycerides, high density lipoprotein, low density lipoprotein) were determined by commercially available kits. Hepatic FXR, BSEP and NTCP gene expression and protein distribution were determined by Reverse Transcription-Polymerase Chain Reaction (RT-PCR) and immunohistochemistry. The results showed that the expression of FXR and BSEP mRNA in the experimental group was higher than that in the control group (P < 0.05). The expression of NTCP mRNA in the control group was higher than that in the experimental group (P < 0.05). Immuno-histological results showed that the positive rates of FXR, BSEP and NTCP expression in the experimental group were significantly different from those in the control group (P <0.05). In conclusion, FXR and Bsep and Ntcp gene changes played an important protective role in lipid metabolism, especially for the rats with high-fat diet.

Au-Ag alloy films of around 60 nm thickness arc deposited on the slab glass substrate by radio frequency sputtering technique. Then large-area uniform nanoporous gold films (NPGF) with strong adhesion arc fabricated by chemical dealloying at room temperature. The resonance spectrum of NPGF exposed to the air in the visible-near-infrared region is obtained by a self-built broadband spectral surface plasmon resonance (SPR) detection platform. The Fresnel formula and Bruggeman dielectric constant approximation equation arc used to fit the experimental results. The porosity of NPGF is about 0.38. The response characteristics of the NPGF-SPR sensor to Pb2+ ions and melamine molecules adsorbed from the individual aqueous solutions with different concentrations arc investigated. The experimental results show that the NPGF-SPR sensor can make obvious responses to both Pb2+ ions and melamine molecules in the aqueous solution with 1 nmol.L-1 concentration. The comparison experiment shows that the NPGF-SPR sensor is much more sensitive than the conventional SPR sensor with a dense gold layer.