An optical fiber magnetic field sensor based on the single-mode-multimode-single-mode (SMS) structure and magnetic fluid (MF) is proposed and demonstrated. By using a piece of no-core fiber as the multimode waveguide in the SMS structure and MF sealed in a capillary tube as the magnetic sensitive media, which totally immersing the no-core fiber, an all-fiber magnetic sensor was fabricated. Interrogation of the magnetic field strength can be achieved either by measuring the dip wavelength shift of the transmission spectrum or by detecting the transmission loss at a specific wavelength. A demonstration sensor with sensitivities up to 905 pm/mT and 0.748 dB/mT was fabricated and investigated. A theoretical model for the design of the proposed device was developed and numerical simulations were performed.

It has long been a challenge to develop strain sensors with large gauge factor (GF) and high transparency for a broad strain range, to which field silver nanowires (AgNWs) have recently been applied. A dense nanowire (NW) network benefits achieving large stretchability, while a sparse NW network favors realizing high transparency and sensitive response to small strains. Herein, a patterned AgNW–acrylate composite-based strain sensor is developed to circumvent the above trade-off issue via a novel ultrasonication-based patterning technique, where a water-soluble, UV-curable acrylate composite was blended with AgNWs as both a tackifier and a photoresist for finely patterning dense AgNWs to achieve high transparency, while maintaining good stretchability. Moreover, the UV-cured AgNW–acrylate patterns are brittle and capable of forming parallel cracks which effectively evade the Poisson effect and thus increase the GF by more than 200-fold compared to that of the bulk AgNW film-based strain sensor. As a result, the AgNW-based strain sensor possesses a GF of ∼10,486 at a large strain (8%), a high transparency of 90.3%, and a maximum stretchability of 20% strain. The precise monitoring of human radial pulse and throat movements proves the great potential of this sensor as a measurement module for wearable healthcare systems.

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A novel strategy to modify the plasmonic interface by spin-coating an overlayer of graphene oxide sheets (GOSs) on top of the surface plasmon resonance (SPR) sensor is proposed and demonstrated. Thanks to the excellent electrical conductivity, large surface area, and high-refractive index of the GOSs layer, the GOSs-modified SPR (GOSs-SPR) sensor achieves an improved sensitivity in the detection of bulky refractive index solutions and bovine serum albumin (BSA) solutions. The maximum sensitivity of 2715.1 nm/RIU achieved by three spin-coatings shows an enhancement of 20.2% than the case without the modification of the GOSs overlayer. Benefiting from the large surface area and abundant surface functional groups, the GOSs-SPR sensor has a greater sensitivity enhancement (up to 39.35%) in the detection of the BSA molecules. Most importantly, we have firstly experimentally demonstrated that the GOSs overlayer with thickness over hundreds nanometers can still lead to a great enhancement of sensitivity of SPR sensors. Additionally, the proposed modification method for the plasmonic interface is a simple and effective strategy to boost the sensitivity in a chemical-free and environment-friendly manner, without additional chemical or biological amplification steps. These unique features make the proposed GOSs-SPR biosensor a low-cost and biocompatible platform in the fields of biochemical sensing, drug screening, and environmental monitoring.

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