In this work, WO₃/TiO₂ core–shell (C-S) nanowires (NWs) were successfully synthesized by the coaxial electrospinning method and subsequent high-temperature calcination treatment. After some microscopic structural characterizations, although the prepared WO₃–TiO₂ and TiO₂–WO₃ C-S NWs displayed quite different surface morphologies, both of the shell coatings were uniform and their typical shell thicknesses were extremely close, with mean values of 22 and 20 nm, respectively. In gas sensing tests, WO₃/TiO₂ C-S NWs exhibited good selectivity towards triethylamine (TEA) without significant interfering gases. Compared with bare WO₃ and TiO₂ NWs, WO₃/TiO₂ C-S NWs showed better gas sensing performance. Specifically, the optimal operating temperature and response of TiO₂–WO₃ C-S NWs to 100 ppm TEA were 130 °C and 106, which were reduced by 70 °C and increased by 5.73 times compared to bare WO₃, respectively. Obviously, the C-S nanostructures contributed to improving the gas sensing performance of materials towards TEA. Finally, some hypothetical sensing mechanisms were proposed, which were expected to have important reference significance for the design of target products applied to TEA sensing.

In this study, a terahertz microfluidic multi-band sensor was designed. Unlike previous microfluidic absorption sensors that rely on dipole resonance, the proposed sensor uses a physical mechanism for absorption by exciting higher-order lattice resonances in microfluidic structures. With a Fabry–Perot cavity, the sensor can form an absorption peak with a high quality factor (Q) and narrow full width at half maximum (FWHM). A high Q value and a narrow FWHM are valuable in the field of sensing and provide strong support for high-precision sensing. On this basis, the sensing performance of the device was investigated. The simulation results clearly show that the absorption sensor has ultra-high sensitivity, which reaches 400 GHz/Refractive Index Unit (RIU). In addition, the sensor generates three absorption peaks, overcoming the limitations of a single frequency band in a composite resonance mode and multidimensional frequency response, which has potential application value in the field of volatile organic compound (VOC) sensing.

Seafood, especially marine fish, is highly prone to spoilage during processing, transportation, and storage. It releases pungent trimethylamine (TMA) gas, which severely affects food quality and safety. Metal–oxide–semiconductor (MOS) gas sensors for TMA detection offer a rapid, convenient, and accurate method for assessing fish freshness. Indium oxide (In₂O₃) has shown potential as an effective sensing material for the detection of TMA. In this work, one-dimensional In₂O₃ nanowires with different grain sizes and levels of crystallinity were synthetized using the electrospinning technique and underwent different thermal calcination processes. Gas-sensing tests showed that the In₂O₃–3 °C/min–500 °C gas sensor exhibited an outstanding performance, including a high response (R_a/R_g = 47.0) to 100 ppm TMA, a short response time (6 s), a low limit of detection (LOD, 0.0392 ppm), and an excellent long-term stability. Furthermore, the sensor showed promising experimental results in monitoring the freshness of Larimichthys crocea (L. crocea). By analyzing the relationship between the grain size and crystallinity of the In₂O₃ samples, a mechanism for the enhanced gas-sensing performance was proposed. This work provides a novel strategy for designing and fabricating gas sensors for TMA detection and highlights their potential for broad applications in real-time fish freshness monitoring.

In recent years, paper-based humidity sensors have emerged as a highly promising technology for humidity detection. In this work, a polymerizable deep eutectic solvent (PDES) was prepared via a one-step blending method, which was applied to modify filter paper. The modification process did not alter the overall structure of the paper cellulose but rather targeted only its internal cellulose channels, thereby minimizing any impact on the paper’s original moisture-independent properties. The filter paper functioned both as the substrate and the humidity-sensing material in the fabricated sensor. The finger-like electrodes were designed using AutoCAD 2018 software and then printed onto the modified paper using screen-printing technology to fabricate the humidity sensor. Different saturated salt solutions were used to simulate corresponding humidity environments and evaluate the humidity performance of sensors. Compared with that of the blank paper-based humidity sensor, the sensitivity of the sensor modified by the PDES was significantly greater, and the recovery time was greatly shorter. Specifically, the sensitivity increased from 1.34 to 10.36 at 54% RH and from 166.24 to 519.2 at 98% RH. Additionally, the sensor response time was reduced from 728 s to 137 s. PDES modification significantly improved the moisture-sensitive characteristics and detection performance of the sensor.

Bound states in the continuum (BICs) can be transformed into quasi-bound states (quasi-BICs) via intentional symmetry breaking, thereby enabling ultrahigh-Q resonances critical for refractometric sensing applications. To advance detection capabilities for organic analytes, we proposed an all-dielectric metasurface monolithically integrated within a microfluidic channel. Mirror symmetry was intentionally disrupted through a cylindrical perturbation applied to one of two identical elliptical resonators, which excited a quasi-BIC mode at 1.9591 THz with a numerically validated Q-factor of 1959. This resonance manifested an absorption peak approaching unity, featuring a full-width at half-maximum (FWHM) of merely 1 GHz. Multipolar decomposition revealed that the mode originated from a synergistic electric-quadrupole (EQ)–magnetic-dipole (MD) pair, wherein the EQ contribution exceeded the MD counterpart by 20%. Capitalizing on this high-Q resonance, the sensor attained a sensitivity of 240 GHz per refractive-index unit (GHz RIU⁻¹) and a figure of merit (FOM = S/FWHM) of 240, while demonstrating robust performance against fabrication tolerances spanning −4% to +4%. Additionally, we verified that oblique-incidence illumination could activate a quasi-BIC within the identical spectral band, circumventing the need for structural asymmetry and thus expanding operational versatility. Benefiting from its geometric simplicity and competitive performance, this architecture exhibited substantial potential for on-chip sensing of organic compounds.

Conventional quasi-bound state in the continuum (quasi-BIC) terahertz (THz) metasurfaces usually operate at fixed resonance frequencies and lack electrically controlled dynamic tunability. To address this limitation, we propose two schemes for realizing liquid-crystal-integrated quasi-BIC THz metasurfaces by exploiting the electrically tunable refractive index of liquid crystals in the THz regime. A microfluidic multilayer architecture combining a liquid-crystal functional layer with a silicon (Si)-based metasurface is constructed, in which the transition from an ideal BIC to a quasi-BIC is realized through two distinct mechanisms: pixelated control of the liquid-crystal orientation and geometric symmetry breaking of the Si resonators. Cartesian multipole decomposition reveals that the resonances in both configurations are dominated by magnetic dipole modes. The effects of the liquid-crystal orientation angle and key geometric parameters on the resonance frequency, peak absorptance, and quality factor are systematically investigated. Numerical results demonstrate continuous tuning of the terahertz resonance through variation in the liquid-crystal orientation angle, corresponding to electrically driven liquid-crystal reorientation in practical devices. The sensing performance of the optimized Si-resonator-based configuration is further evaluated, achieving a refractive index sensitivity of 117 GHz RIU⁻¹ and a figure of merit (FOM) of 146.25. This work overcomes the fixed-frequency limitation of conventional static quasi-BIC metasurfaces and provides a feasible route toward electrically reconfigurable terahertz microfluidic sensing devices with tunable operating frequencies.