A compact, simple-to-fabricate, low-cost, and highly sensitive optical fiber temperature sensor based on surface plasmon resonance (SPR) is reported. The sensor consists of a core mismatch fiber structure fabricated by splicing a small piece of single-mode fiber (SMF) between two multimode fibers (MMF). SPR is generated when evanescent field interacts with the gold layer deposited over the SMF cladding. Then, the sensor was embedded in polydimethylsiloxane (PDMS), which acts as a temperature to refractive index transducer. Due to PDMS high thermooptic coefficient, the SPR dip underwent a noticeable wavelength shift when a variation of temperature occurred. The device was tested in the 20-60 °C range showing a linear response and a sensitivity of 2.60 nm/°C. This sensor is appealing for temperature monitoring in microfluidic devices made of PDMS due to its high performance and simply fabrication process.

This paper provides the design, fabrication, and experimental demonstration of a novel, compact, and simple-to-construct optical fiber-tip sensor for the simultaneous measurement of the refractive index (RI), temperature, and level of liquid samples by means of Surface Plasmon Resonance (SPR) phenomenon. The proposed fiber-tip SPR sensor consists of a multimode fiber (MMF) spliced to a sensing element, it comprises a gold-coated single-mode fiber (SMF) tip, whose end-face is coated with a metallic mirror. By covering part of the sensing element with a thermo-responsive material, whose thermo-optic coefficient (TOC) is high, it is possible to measure temperature; whereas the metal-bare section is used to measure the changes in the RI and level of a liquid sample. As the RI and temperature of the liquid sample increase, the position of the resonance wavelengths ( $\lambda_bare$ and $\lambda_Covered$ ) shifts towards larger and shorter wavelengths, respectively. On the other hand, as the level of the sensed sample increases, the deepness of $\lambda_bare$ increases too, but the position of $\lambda_bare$ and $\lambda_Covered$ remains constant for a particular liquid and temperature. We expect that this novel sensor becoming a promising candidate for biomedical, food, and industrial applications.

Embedded sensors (ESs) are used in smart materials to enable continuous and permanent measurements of their structural integrity, while sensing technology involves developing sensors, sensory systems, or smart materials that monitor a wide range of properties of materials. Incorporating 3D-printed sensors into hosting structures has grown in popularity because of improved assembly processes, reduced system complexity, and lower fabrication costs. 3D-printed sensors can be embedded into structures and attached to surfaces through two methods: attaching to surfaces or embedding in 3D-printed sensors. We discussed various additive manufacturing techniques for fabricating sensors in this review. We also discussed the many strategies for manufacturing sensors using additive manufacturing, as well as how sensors are integrated into the manufacturing process. The review also explained the fundamental mechanisms used in sensors and their applications. The study demonstrated that embedded 3D printing sensors facilitate the development of additive sensor materials for smart goods and the Internet of Things.

A simple method to construct a dual-channel in a prism-based surface plasmon resonance sensor for dual-parameter monitoring is proposed. The metal layer (sensing area), attached to the prism, is half-covered with a polymer in order to generate two individual sensing sections. In this work, eight different sensor structures (prism/metal/polymer) were analyzed. The prisms are made of NSK16 or SF10 glass and coated with gold or silver films. Half section of the metal films is covered with Polydimethylsiloxane (PDMS) or Poly-methyl methacrylate (PMMA). The sensor is based on angle interrogation, the laser beam is aligned to be incident upon the interface of the bare and polymer sections. The resonance conditions are different at each pad, due to the refractive index (RI) mismatch, thus the intensity of the reflected signal presents a pair of well-defined resonance dips in series. The sensitivity of these dips to RI and temperature (T) changes was numerically analyzed. Finally, to demonstrate the feasibility to monitor RI and T simultaneously, a SPR sensor was constructed using a NSK16 glass prism coated with a thin gold film, which was half-covered with PDMS.

Researchers and the space industry benefit greatly from the development and research of new sensors based on carbon nanomaterials in 1D and 2D. Despite new carbon nanomaterials (CNMs) having numerous advantages, developing sensors based on these materials still faces numerous challenges due to their needs of precision, reliability, and durability. Due to the unique structure of 1D and 2D CNMs such as graphene and carbon nanotubes (CNT), the observed characteristics can be used for the development of high-performance sensors. Therefore, such materials have recently been used to produce cutting-edge sensor materials for satellites in LEO (low earth orbit) and VLEO (very low earth orbit). In this article, we explain the importance of CNMs-based sensors in satellite and space transportation. A key benefit of these new CNM-based sensors is that they can detect signals with high accuracy and reliability, which makes it easier for researchers to choose and manufacture sensor materials.