Anti-resonant hollow core fiber with excellent bending resistance in the visible spectral range.

The development of wideband guided hollow-core anti-resonant fiber (HC-ARF) that covers the sensitive range of the human eye's visible spectrum is progressing rapidly. However, achieving low-loss wideband transmission with a small bending radius remains a challenging issue to be addressed. In light of this, we propose a novel, to our knowledge, HC-ARF with a nested double-semi-elliptical cladding structure in the visible spectral region. By employing finite element method simulations, we investigate the confinement loss, bending loss, and single-mode performance of this fiber design. The result shows that the confinement loss of this new fiber exhibits below 10-5 dB·m-1 across almost the entire visible band range, with a minimum loss of 1.55 × 10-7 dB·m-1 achieved for λ = 650 nm. Furthermore, this fiber demonstrates excellent resistance to bending and can maintain an ultra-low bending loss as low as 3 × 10-7 dB·m-1 even under extreme bending conditions with a radius of only 3 cm. Notably, its 3-dB bending radius reaches just 3.5 cm for λ = 532 nm. Additionally, it exhibits outstanding single-mode conductivity under various bending scenarios and achieves a high extinction ratio of up to 104 for higher-order modes after parameter optimization for specific wavelengths.

Bioinspired Stretchable MXene Deformation-Insensitive Hydrogel Temperature Sensors for Plant and Skin Electronics.

Temperature sensing is of high value in the wearable healthcare, robotics/prosthesis, and noncontact physiological monitoring. However, the common mechanic deformation, including pressing, bending, and stretching, usually causes undesirable feature size changes to the inner conductive network distribution of temperature sensors, which seriously influences the accuracy. Here, inspired by the transient receptor potential mechanism of biological thermoreceptors that could work precisely under various skin contortions, we propose an MXene/Clay/poly(N-isopropylacrylamide) (PNIPAM) (MCP) hydrogel with high stretchability, spike response, and deformation insensitivity. The dynamic spike response is triggered by the inner conductive network transformation from the 3-dimensional structure to the 2-dimensional surface after water being discharged at the threshold temperature. The water discharge is solely determined by the thermosensitivity of PNIPAM, which is free from mechanical deformation, so the MCP hydrogels can perform precise threshold temperature (32 °C) sensing under various deformation conditions, i.e., pressing and 15% stretching. As a proof of concept, we demonstrated the applications in plant electronics for the real-time surface temperature monitoring and skin electronics for communicating between human and machines. Our research opens venues for the accurate temperature-threshold sensation on the complicated surface and mechanical conditions.

2D PtSe2 Enabled Wireless Wearable Gas Monitoring Circuits with Distinctive Strain-Enhanced Performance.

The application of 2D materials-based flexible electronics in wearable scenarios is limited due to performance degradation under strain fields. In contrast to its negative role in existing transistors or sensors, herein, we discover a positive effect of strain to the ammonia detection in 2D PtSe2. Linear modulation of sensitivity is achieved in flexible 2D PtSe2 sensors via a customized probe station with an in situ strain loading apparatus. For trace ammonia absorption, a 300% enhancement in room-temperature sensitivity (31.67% ppm-1) and an ultralow limit of detection (50 ppb) are observed under 1/4 mm-1 curvature strain. We identify three types of strain-sensitive adsorption sites in layered PtSe2 and pinpoint that basal-plane lattice distortion contributes to better sensing performance resulting from reduced absorption energy and larger charge transfer density. Furthermore, we demonstrate state-of-the-art 2D PtSe2-based wireless wearable integrated circuits, which allow real-time gas sensing data acquisition, processing, and transmission through a Bluetooth module to user terminals. The circuits exhibit a wide detection range with a maximum sensitivity value of 0.026 V·ppm-1 and a low energy consumption below 2 mW.

Conductive Porous MXene for Bionic, Wearable, and Precise Gesture Motion Sensors.

Reliable, wide range, and highly sensitive joint movement monitoring is essential for training activities, human behavior analysis, and human-machine interfaces. Yet, most current motion sensors work on the nano/microcracks induced by the tensile deformation on the convex surface of joints during joint movements, which cannot satisfy requirements of ultrawide detectable angle range, high angle sensitivity, conformability, and consistence under cyclic movements. In nature, scorpions sense small vibrations by allowing for compression strain conversion from external mechanical vibrations through crack-shaped slit sensilla. Here, we demonstrated that ultraconformal sensors based on controlled slit structures, inspired by the geometry of a scorpion's slit sensilla, exhibit high sensitivity (0.45%deg-1), ultralow angle detection threshold (~15°), fast response/relaxation times (115/72 ms), wide range (15° ~120°), and durability (over 1000 cycles). Also, a user-friendly, hybrid sign language system has been developed to realize Chinese and American sign language recognition and feedback through video and speech broadcasts, making these conformal motion sensors promising candidates for joint movement monitoring in wearable electronics and robotics technology.

Efficient Full-Color Boron Nitride Quantum Dots for Thermostable Flexible Displays.

Hexagonal boron nitride quantum dot (BNQD) has aroused great interest in the optoelectronics field due to their metal-free nature with promising optical properties. However, it has been a great challenge to modulate its photoluminescence to the long-wavelength region so far. Herein, BNQDs with full-color emission (420-610 nm) have been implemented by doping diverse amino ligands in different solvents for the first attempt. This color variation from blue, green, yellow-green, yellow to red is ascribed to the surface states tunable via amination degree. Attractively, the quantum yield of our blue BNQDs has set a record at 32.27%, and rare yellow-green BNQDs have been demonstrated. Combining good thermal dissipation capability and high transparency, our full-color BNQD holds great potential for transparent flexible display and security labels at the elevated temperature.