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• A new D-shape fiber long period fiber grating (DLPFG) curvature sensor has been experimentally proposed and theoretically investigated, LPFG was directly inscribed on polished area of D-shape fiber by high-frequency CO 2 laser, who has a high curvature sensitivity of 17.6 nm/m−1. The sensitivity is higher than that of other types of LPFGs inscribed on D-shape SMF. • The influence of high-frequency CO 2 laser polishing on resonance peak loss, wavelength position and curvature sensitivity has been investigated. • The proposed DLPFG curvature sensor also has deep resonant peak, good linearity, reproducibility, repeatability and low temperature crosstalk. In this paper, a D-shape fiber long period fiber grating (DLPFG) curvature sensor has been theoretically and experimentally investigated. Different from previous reported long period fiber grating (LPFG) curvature sensor based on D-shape single mode fiber (SMF), the fabrication of DLPFG is divided into two steps: LPFG with a low coupling efficiency is firstly written on a SMF by high-frequency CO 2 laser, and then the grating area is subsequently polished to induce deeper resonance peaks and D-shape structure simultaneously. The polishing greatly enhances the fiber asymmetric modulation and thus results in the improvement of curvature sensitivity. Experiments show that the DLPFG has a high curvature sensitivity of 17.6 nm/m−1 and −11.9 nm/m−1 in two opposite directions within the plane perpendicular to CO 2 laser-irradiated direction, which has exceeded that of the other reported LPFGs based on D-shape SMF. Besides, the temperature sensitivity is 45 pm/°C in range of −20 °C to 50 °C, and the temperature cross sensitivity is 2.58 × 10-3 m−1/°C. Therefore, this proposed DLPFG sensor with advantages of low-cost, easy-fabrication, high-reproducibility and high-sensitivity is promising for curvature measurement. [ABSTRACT FROM AUTHOR]

In autumn and winter, the climate is dry and human skin tends to become dry as a result. The application of hyaluronic acid to a fabric has a certain moisturizing effect, which can further improve the wearing comfort of the fabric. In this study, three knitted fabric structures including weft plain stitch, 1 + 1 mock rib, and 1 + 3 mock rib were designed. The face yarn adopted hyaluronic acid viscose fiber, graphene viscose fiber, nylon, and viscose with different interweaving ratios, and the inner yarn adopted nylon/spandex-coated wire. A total of 18 sample knitted fabrics were woven according to the experimental method of the full test. The effects of the fabric structure and fabric raw materials on skin moisturizing properties were studied and analyzed by testing the skin water content and trans-epidermal water loss before and after coating the fabric on the human skin. The results show that the most significant factor affecting the skin moisture content is the raw material used in the fabric. When the interweaving ratio of hyaluronic acid viscose fiber in the fabric decreases, the moisturizing performance of the fabric on human skin is weakened. The second is the fabric structure. In terms of structure, 1 + 1 mock rib fabric has better moisturizing performance for human skin. When the material adopts hyaluronic acid viscose fiber/graphene viscose fiber (100:0) and the structure adopts 1 + 1 mock rib, the moisturizing effect on human skin is better. [ABSTRACT FROM AUTHOR]

• A LPFG sensor based on bend insensitive SMF has been proposed and investigated for the measurement of seawater salinity, and its sensitivity also has been comprehensively optimized by fully combining MT and reducing cladding diameter. • Compared with the LPFG based on traditional SMF, the proposed sensor achieved a low curvature sensitivity of 0.889 nm/m−1 in the curvature range of 0–2.25 m−1, which makes it have a strong resistance to bending interference in the process of seawater salinity measurement. • The maximum RI sensitivity reaches to 954.18 nm/RIU, which is about 5.9 times higher than that of the unoptimized LPFG, and an average sensitivity of 163.299 pm/‰ can be achieved when seawater salinity changes from 5.001 to 39.996 ‰ due to the contribution of reducing cladding diameter and MT. In this work, we proposed a long period fiber grating (LPFG) seawater salinity sensor based on a bend insensitive single mode fiber (SMF). The average curvature sensitivity of LPFG in the most sensitive direction is 0.889 nm/m−1 in curvature range of 0 m−1–2.25 m−1. A comprehensive design method was proposed to optimize the sensitivity of seawater salinity by fully combining mode transition (MT) and reducing cladding diameter. The enhancing effects of MT and reducing cladding on surrounding refractive index (SRI) sensitivity were discussed, respectively. After reducing the cladding diameter by hydrofluoric acid (HF) etching, a layer of titanium dioxide (TiO 2) nanofilm was deposited on the surface of LPFG by electrostatic self-assembly technology. The average seawater salinity sensitivity of 163.299 pm/‰ can be achieved in salinity range of 5.001 ‰–39.996 ‰. The experimental results are well agreement with theoretical analysis. [ABSTRACT FROM AUTHOR]