The very long wave infrared (VLWIR, 15-30 mu m) band is critical for applications such as astronomical observation, meteorological monitoring, and stealth detection due to its high atmospheric transmittance and rich spectral information. Conventional cooled IR detectors, however, require extremely low operating temperatures and are limited by the bandgap of semiconductor materials, restricting their spectral coverage and increasing cost. Here, we present a low-noise uncooled VLWIR detector based on a Y-cut quartz bulk acoustic wave (BAW) resonator. By exploiting the high temperature coefficient of frequency (TCF) of quartz and its intrinsic VLWIR absorption, the device enables room-temperature detection of VLWIR radiation. A differential configuration was implemented to suppress environmental temperature drift, reducing frequency noise by nearly three orders of magnitude. In a custom-built VLWIR testing platform, the detector achieved a responsivity (R) of 30.8 MHz/W and a noise-equivalent temperature difference (NETD) as low as 5.4 mK, approaching the performance of many cooled detectors. Moreover, proof-of-concept CO2 sensing experiments demonstrated the potential of this approach for gas detection. This work provides, to our knowledge, a novel technical strategy to overcome the performance limitations of uncooled IR detectors in the VLWIR band and establishes a foundation for room-temperature VLWIR sensing applications. (c) 2026 Chinese Laser Press

Honeycomb-structured and high-Curie-point positive temperature coefficient (PTC) heating elements are promising for thermal management in hydrogen fuel cell vehicles, which require highly safe and efficient hydrogen supply and fuel cell start-up. However, it is still challenging to prepare honeycomb structures by traditional manufacturing methods because of the high dependence on molds and poor mixing uniformity of raw materials. Additionally, the poor curing performance of leaded PTC ceramic slurry tends to hinder the preparation of complex geometries by the emerging digital light processing (DLP) 3D printing. Herein, an innovative method for functionalizing PTC powder, introducing polymethyl methacrylate (PMMA) and Al2O3, and optimizing the honeycomb structure was developed to fabricate high-performance PTC ceramics in this study. Notably, with 10 vol% PMMA and 3 vol% Al2O3, a low room-temperature resistivity (rho = 42 Omega cm), a high temperature coefficient of resistance (alpha 10-25 = 15.02%/degrees C) and a large PTC jump (log(Rmax/Rmin) = 4.01) are obtained, showing significant improvement over unmodified printed PTC ceramics (rho = 225 Omega cm, alpha 10-25 = 8.03%/degrees C, and log(Rmax/Rmin) = 2.59) while slightly outperforming conventionally pressed PTC ceramics (rho = 71 Omega cm, alpha 10-25 = 15.89%/degrees C, and log(Rmax/Rmin) = 3.93). Meanwhile, the experimental and simulation results indicate that the honeycomb structure with 60% porosity exhibits excellent electrical properties, rapid thermal response and strong heat storage capacity for hydrogen supply and fuel cell preheating. Therefore, this work provides a viable strategy for additive manufacturing of advanced functional ceramics with customized structural designs for sensors and heaters.

ABSTRACT Frequent blood testing remains invasive and impractical, hindering real‐time health monitoring. Interstitial fluid (ISF) offers a promising alternative, yet current microneedle platforms are complex, inefficient, and lack multiplexing capability. Here, we present a portable and dual‐button microneedle device for rapid ISF sampling, coupled with multimodal laser sensing for molecular and elemental analysis. The disposable device has a low material cost (< 2 USD). The dual‐button design ensures user‐friendly microneedle operation, while the hollow microneedles with built‐in microfluidic channels enable ISF sampling within 1 min. In parallel, gold nanocubes coupled with MXene are engineered as a sensing module, providing signal enhancement for laser spectroscopy in molecular and elemental analysis. Furthermore, artificial intelligence (AI)‐assisted data processing enhances spectral data interpretation for comprehensive health assessment. Both in vitro and in vivo studies demonstrate promising performance (with accuracies exceeding 88%). This user‐friendly, rapid, cost‐effective, and multiplexed device offers a powerful route toward clinical translation, bridging the gap between advanced laser spectroscopy and point‐of‐care applications.

Gyrotropic effects, including natural optical activity (NOA) and the nonlinear anomalous Hall effect (NAHE), are crucial for advancing optical and transport devices. We explore these effects in the BaTiS3 system, a quasi-one-dimensional crystal that exhibits giant optical anisotropy. (Niu et al. Nat. Photonics 12, 392 (2018); Zhao et al. Chem. Mater. 34, 5680 (2022)). In the P63cm phase which is stable under room temperature, we predict two distinct strain-induced phase transitions: a symmetry-lowering transition from the P63cm to P63 phase under tensile strain, which enhances NOA and enables optical rotation; and an isostructural insulator-to-polar Weyl semimetal (WSM) transition under compressive strain, which activates the NAHE and exhibits a strain-induced sign reversal. The low-temperature P21 phase also transforms into a P212121 phase under enough compressive strains with such phase transition exhibiting a large NOA. All these results highlight BaTiS3 as a viable candidate for novel ferroelectrics, optical and transport devices with strain enhanced or activated gyrotropic properties.

Hollow CuO–SnO 2 nanospheres deliver stable ppb-level H 2 S sensing in an aerospace environment.

The toxicity of lead in perovskite solar cells has long been a significant barrier to their widespread commercialization. The improvement of environmentally friendly tandem solar cells presents the additional challenge of identifying highly efficient materials for both the wide-bandgap top cell and the narrow-bandgap bottom cell. In this study, we have reported a lead-free, non-toxic tandem perovskite solar cell , investigated through numerical simulations, by pairing an Sb³⁺-doped double perovskite, Cs2AgBi0.75Sb0.25Br6, with a bandgap of 1.8 eV, as the top cell, with a tin-based MASnI₃ bottom cell, which has a bandgap of 1.3 eV. Upon optimization, the simulated device achieves an open-circuit voltage of 2.29 V, a current density of 15.5 mA/cm², and a remarkable photovoltaic conversion efficiency of 26.8%. These results are on par with the performance of state-of-the-art Pb-based tandems, highlighting the competitiveness of Pb-free materials. These simulation results highlight the potential of lead-free perovskite tandem architectures for environmentally sustainable, high-efficiency photovoltaic applications.

Strengthening magnetoacoustic coupling is crucial to the improvement of surface acoustic wave (SAW)-driven spintronics devices. A key challenge in enhancing magnetoacoustic coupling is minimizing the phonon dissipation of the SAW device, which usually requires complicated SAW engineering. This paper presents the observation of an order-of-magnitude enhancement of the magnetoacoustic coupling within a Co/Cu/Ni-Fe multilayer structure deposited on a LiNbO3 piezoelectric substrate. This enhancement is driven by spin current transmission, facilitated by the nonparallel alignment of magnetizations between the Co layer and the Ni-Fe layer. This work provides a versatile platform for advancing magnetoacoustic coupling devices based on the principle of spin current, which exhibits potential for next-generation on-chip SAW spintronics devices.

Surface acoustic wave radio frequency identification (SAW RFID) has gained widespread adoption in remote sensing and identification. However, conventional SAW RFID tags suffer from significant energy loss due to the inherently low reflectance of standard reflectors, fundamentally limiting their wireless interrogation range. To address this limitation, this paper proposes a novel SAW RFID architecture employing reflective multistrip couplers (RMSCs), which exploit the velocity difference between symmetric and antisymmetric wave modes to achieve coherent reflection, thereby circumventing conventional electrical or mechanical reflection mechanisms. Numerical simulations were conducted to analyze performance deterioration induced by parasitic resistances and capacitance and to identify the optimal strip number for peak reflectance. The fabricated RMSC reflector achieves a low loss of 1 dB, with a reflectance difference of merely 0.33 dB compared to the simulation results. A 433 MHz SAW RFID prototype implementing RMSC reflectors on a 128°YX-LiNbO3 single-crystal substrate demonstrated a −10.63 dB peak time-domain amplitude at room temperature, representing a substantial improvement over conventional designs. Temperature characterization from −20 °C to 90 °C revealed linear functions in time delay and phase responses, with coefficients of determination (R2) exceeding 0.9999. These results validate the RMSC reflector as a high-reflectance solution for enhancing SAW RFID performance, suggesting significant potential for long-range wireless sensing applications.

Chemiresistive gas sensors based on semiconducting metal oxides for toxic gas detection are widely explored for terrestrial applications under ambient environments, but their potential in extraterrestrial applications remains underexplored. Herein, we developed porous Cu-doped SnO2 microspheres, enabling high sensitivity and selectivity toward hydrogen sulfide (H2S), from the ambient air (25°C, 105 Pa) to extreme conditions (-40°C, ∼10- 4 Pa) designed to simulate the space-like oxygen defects and cryogenic environments. Hierarchical porosity enables efficient gas diffusion across pressure regimes, and Cu2 + doping and oxygen vacancies thus enable oxygen-independent chemisorption. Moreover, in situ-formed chemical adsorption promotes interfacial charge transfer, which exhibits partial reversibility. The semi-quantitative framework represented by a CuS kinetic proxy, combining numerical simulations based on Wolkenstein adsorption theory, finite element methods, and experimental results, reveals a dual-mechanism paradigm. At ambient conditions, the oxygen-adsorption-driven redox reaction is dominant. In contrast, under a vacuum around 10-4 Pa, direct chemisorption and interfacial charge transfer primarily govern the gas adsorption responses. This study offers a generalized metal-oxide platform for gas detection for future space exploration and life-support monitoring systems.

Structural modification is a feasible and effective method to improve the heating efficiency and uniformity of BaTiO3-based ceramics with positive temperature coefficient (PTC) of resistance. However, modifying threedimensional (3D) structures by traditional manufacturing methods is very challenging due to the inhomogeneous mixing of raw materials and high mold dependency. Additionally, the realization of complex structures using emerging vat photopolymerization (VPP) technology is limited by the poor curing properties of leaded PTC ceramic slurry. Herein, this study presents an innovative approach of combining VPP technology with vacuum infiltration (VI) process for fabricating high-performance PTC ceramics. Notably, the introduction of soluble starch significantly enhances the curing depth and printability of PTC ceramic slurry. Meanwhile, silica nano-particles in silica sols are infiltrated into 3D printed green bodies to improve the electrical properties of PTC ceramics. At optimal soluble starch content and silica concentration, a lower room temperature resistivity (rho=207 S2 center dot cm) and a higher temperature coefficient of resistance (alpha 0-15=25.14 %/degrees C) are obtained in printed PTC ceramics compared to dry pressed PTC ceramics (rho=301 S2 center dot cm, alpha 0-15=19.32 %/degrees C). Therefore, this work provides a novel technological strategy for fabricating high-performance PTC ceramics with desirable structures and can promote the wide application of PTC heating elements.

We predict high-velocity magnetic domain wall (DW) motion driven by out-of-plane acoustic spin in surface acoustic waves (SAWs). We demonstrate that the SAW propagating at a 30-degree angle relative to the x-axis of a 128 degree Y-LiNbO3 substrate exhibits uniform spin angular momentum, which induces the DW motion at a velocity exceeding 50 m/s, significantly faster than previous DW motions at about 1 m/s velocity driven by conventional SAWs. This remarkable phenomenon highlights the potential of acoustic spin in enabling rapid DW displacement, offering an innovative approach to developing energy-efficient spintronic devices.

Exceptional point (EP) is referred to degeneracies in a non-Hermitian system where two or more eigenvalues and their corresponding eigenvectors coalesce. Recently there have been significantly increased interests in harnessing EPs to enhance responsivities and achieve ultrasensitive detections in optics, electronics and acoustics, although there are few similar studies focused on using surface acoustic wave (SAW) sensing technologies, probably due to its great technical challenges. Herein, we proposed a scheme for accessing EPs in an on-chip architecture consisted of coupled-SAW-resonators system, forming a passive parity-time (PT) symmetric system. We demonstrated that by tuning additional losses in one of resonators and regulating the system in the proximity of the EP, the sensor exhibited significantly enhanced responses. As an example, we present an EP-based SAW gas sensor, which showed a much-improved sensitivity compared to that of a conventional delay-line SAW sensor. The fundamental mechanisms behind this excellent sensing performance have been elucidated.

This study investigated the impact of zinc oxide’s (ZnO’s) morphology on the piezoelectric performance of polyvinylidene fluoride (PVDF) composites for flexible sensors. Rod-like (NR) and sheet-like (NS) ZnO nanoparticles were synthesized via hydrothermal methods and incorporated into PVDF through direct ink writing (DIW). The structural analyses confirmed the successful formation of wurtzite ZnO and enhanced β-phase content in the PVDF/ZnO composites. At a degree of 15 wt% loading, the ZnO-NS nanoparticles achieved the highest β-phase fraction (81.3%) in PVDF due to their high specific surface area, facilitating dipole alignment and strain-induced crystallization. The optimized PVDF/ZnO-NS-15 sensor demonstrated superior piezoelectric outputs (4.75 V, 140 mV/N sensitivity) under a 27 N force, outperforming its ZnO-NR counterparts (3.84 V, 100 mV/N). The cyclic tests revealed exceptional durability (<5% signal attenuation after 1000 impacts) and a rapid response (<100 ms). The application trials validated their real-time motion-monitoring capabilities, including finger joint flexion detection. This work highlights the morphology-dependent interfacial polarization as a critical factor for high-performance flexible sensors, offering a scalable DIW-based strategy for wearable electronics.

We predict high-velocity magnetic domain wall(DW)motion driven by out-of-plane acoustic spin in surface acoustic waves(SAWs).We demonstrate that the SAW propagating at a 30-degree angle relative to the x-axis of a 128° Y-LiNbO3 substrate exhibits uniform out-of-plane spin angular momentum.This acoustic spin triggers the DW motion at a velocity exceeding 50m/s in a way that is similar to the spin-transfer-torque effect.This phenomenon highlights the potential of acoustic spin in enabling rapid DW displacement,offering an innovative approach to developing energy-efficient spintronic devices.

We report an unconventional twofold-symmetric magnetoelastic coupling in Ni films, mediated by Rayleigh surface acoustic waves (SAWs). This unique magnetoelastic symmetry originates from a dominant vertical shear strain ϵ_{yz}, which becomes prominent due to the low effective elastic modulus of Ni film. As the film thickness increases, ϵ_{yz} surpasses the conventional Rayleigh SAW strain ϵ_{xx}, a consequence originated from the elastic modulus mismatch at the film-substrate interface. This finding highlights the dominance of ϵ_{yz} in soft thin film under SAW excitation, offering a new platform to excite strong nonreciprocal and topological magnon-phonon hybridization.

Resonators are passive devices that respond to an excitation signal by oscillating at their natural frequency with exponentially decreasing amplitudes. Physical, chemical and electrical variables can modify the natural frequencies of resonators. If resonators are connected to antennas or other transducers that couple into a communication channel, they enable purely passive sensors that can be read wirelessly. In this manuscript, we use maximum likelihood estimation to analyze the measurement accuracy that can be achieved by the wireless readout of passive resonant sensors as a function of the read signal, the stimulation power and noise figure of the reader, the distance and transducer gain of the transmission channel, and the natural frequency and quality factor of the resonant passive sensor. The Crámer–Rao lower bound characterizes the minimum variance of the natural frequency and decay constant of the resonator. We show the derivation of the Crámer–Rao lower bounds from the Fisher information matrix based on a maximum likelihood estimation of discrete-time samples of an exponentially decaying phasor. This theoretical lower limit of accuracy is almost achieved by an iterative algorithm that approximates the maximum of the measured resonator spectrum with a Lorentz curve.

Toxic gas sensors are widely used on Earth, but few are developed for their applications in outer space. Conventional metal oxide semiconductor (MOS) sensors are commonly operated at high temperatures (>100 degrees C), which hinder their capabilities for detecting many toxic and explosive gases. Additionally, operating at elevated temperatures compromises their energy efficiency and long-term reliability, especially in space environment (approximately 10(-)(12) Pa). Herein, we developed a p-n heterojunction-based MOS thin film gas sensor, assisted with an ultraviolet light emitting diode (UV-LED) irradiation method, operated at room temperature and vacuum condition (around 10(-)(3) Pa). SnO2-CuO and ZnO-CuO thin films for detecting hydrogen sulfide (H2S) gas were chosen as examples in this study. The UV-LED (365 nm) enhanced chemical reactions between H2S and CuO significantly improved sensor performance, and the developed H2S sensor exhibited a remarkable sensitivity, with a response of 9799 for 25 ppm H2S. The sensor demonstrated good selectivity in the presence of various interfering gases such as CO, H-2, and NO2, and showed its great potential for future space exploration applications.

Wearable epidermal sensors can realize real-time, minimally invasive or noninvasive monitoring of biomarkers such as those found in sweat, interstitial fluid (ISF), and wound exudate. Conventional electrochemical and colorimetric sensing techniques face challenges in achieving reliable multiplexed detection. Surface-enhanced Raman spectroscopy (SERS) can offer molecular specificity for detecting trace biomarkers. This review examines the use of SERS in epidermal sensors, with a focus on material design, substrate functionalization, and biofluid sampling strategies. We discuss opportunities for future development in device structural design, the use of plasmonic materials, multi-functional integration, and AI-driven diagnostics.

A multimodal Laser Opto-Ultrasonic Dual Detection (LOUD) technique is presented in this work for the comprehensive characterization of BaTiO3 ceramics doped with varying Sn concentrations. The main objective was to evaluate these materials' quantitative elemental composition, grain size, and porosity simultaneously, thus overcoming the constraints of conventional approaches that necessitate separate instruments and procedures. The synthesis of Sn-doped BaTiO3 ceramics was carried out using a solid-state reaction method, with nominal Sn doping concentrations ranging from 0 % to 20 %. The findings revealed a mean grain size of 8.88 μm and a standard deviation of ±3.80, alongside a mean porosity of 11.43 % with a standard deviation of ±2.30, regardless of doping concentrations. The findings indicated that higher Sn concentration resulted in a notable decrease in grain size from 14.39 μm in pure BaTiO3 to 4.08 μm in BaTiO3 doped with 20 % Sn, accompanied by a corresponding increase in porosity from 9.25 % to 13.66 %. The samples were evaluated quantitatively using the LOUD technique, combining laser-induced breakdown spectroscopy (LIBS) and laser ultrasonics (LU) to assess their compositional, structural, and mechanical characteristics. Optical signal processing in the LOUD technique enabled accurate quantitative compositional analysis via the calibration-free LIBS technique, revealing precise concentrations of Ba, Ti, and Sn, with a proportional increase in Sn content relative to the doping levels. Meanwhile, ultrasonic signal processing enables accurate grain size and porosity determination by LU parameters (attenuation coefficient and velocities). The correlation analysis of the LU parameters in evaluating grain size (R2 = 0.989) and porosity (R2 = 0.995) demonstrated good reliability compared to the results obtained from traditional electron microscopy and Micromeritics testing. This study validates the LOUD technique's effectiveness in providing a thorough, simultaneous analysis and reinforces its potential as a valuable tool for advancing materials science research.

Microring resonators (MRRs) offer the advantages of easy integration and broad bandwidth for acoustic sensing applications, but they face challenges such as low sensitivity and complex, high-cost fabrication processes. In this paper, we propose polymer-based MRRs using a composite diaphragm to enhance the underwater acoustic sensitivity, based on the significant geometrical deformation of the MRR on the acoustic-sensitive composite diaphragm, along with a polymer refractive index change induced by the photoelastic effect. The devices are manufactured via a novel multiscale fabrication platform that synergizes MEMS techniques for micron-scale diaphragm patterning with high-throughput nanoimprint lithography (NIL), potentially enabling nano-scale optical waveguide features at wafer-level scalability and much lower cost than conventional deep-ultraviolet (DUV) and E-beam lithography approaches. Experimental results show that the sensors effectively respond to underwater acoustic waves ranging from 10 Hz to 10 kHz. They exhibit an average acoustic pressure sensitivity level of -185.9 dB re 1 V/mu Pa from 10 Hz to 1 kHz, with a flatness of 2.6 dB, representing a similar to 32.1 dB improvement compared to traditional devices. The noise equivalent pressure (NEP) is 95.5 dB re 1 mu Pa/root Hz, corresponding to a minimum detectable pressure of 59.8 mPa/root Hz at 1 kHz. These miniature optical acoustic sensors show great potential for accurate underwater target detection and positioning for future underwater vehicles and robotics.