A plasmonic refractive index nanosensor structure consisting of a metal-insulator-metal (MIM) waveguide with two symmetrical rectangle baffles coupled with a connected-concentric-double rings resonator (CCDRR) is presented. In this study, its transmission characteristics were investigated using the finite element method (FEM). The consequences, studied via simulation, revealed that the transmission spectrum of the system presents a sharp asymmetric Fano profile due to the destructive interference between the wide-band mode of two rectangle baffles on the bus waveguide and the narrow-band mode of the CCDRR. The effects of the geometric parameters of the structure on the transmission characteristics were investigated comprehensively. A sensitivity of 2260 nm/RIU and figure of merit (FOM) of 56.5 were the best levels of performance that the designed structure could achieve. In addition, the system could act as a sensor for use for temperature sensing, with a sensitivity that could reach 1.48 nm/°C. The designed structure advances with technology with new detection positions and has good application prospects in other high-sensitivity nanosensor fields, for example, acting as a biosensor to detect the hemoglobin level in the blood.

With the continuous progress of artificial intelligence and other manufacturing technologies, there is promising potential for wearable piezoresistive sensors in human physiological signal detection and bionic robots. Here, we present a facile solution-mixing process to fabricate a multiwalled carbon nanotube/graphite powder (MWCNT@Gp) film, which has high sensitivity and great linearity and is more oriented to flexible piezoresistive sensors. The sensor consists of two parts: a spinosum microstructure shaped by a sandpaper template and polydimethylsiloxane (PDMS) as the top substrate and interdigital electrodes as the bottom substrate. The experiments we have conducted show that these two parts provide good protection to the MWCNTs@Gp film and improve sensor sensitivity. Additionally, the sensitivity of the optimal ratio of multiwalled carbon nanotubes and graphite powder is analyzed. The 5%MWCNT@5%Gp composites were found to have relatively good conductivity, which is convenient for the fabrication of conductive films of piezoresistive sensors. Finally, we conducted application experiments and found that the flexible piezoresistive sensor can detect minute signals of human motion and different pressure points. This indicates the feasibility of portable sensors in electronic skin and smart devices.

This paper proposes a nanosensor structure consisting of a metal–insulator–metal (MIM) waveguide with a rectangular root and a double-ring (SRRDR) with a rectangular cavity. In this paper, the cause and internal mechanism of Fano resonance are investigated by the finite element method (FEM), and the transport characteristics are optimized by changing various parameters of the structure. The results show that the structure can achieve double Fano resonance. Due to the destructive disturbance between the wideband mode of the inverted rectangle on the bus waveguide and the narrowband mode of the SRRDR, the output spectrum of the system shows an obvious asymmetric Fano diagram, and the structural parameters of the sensor have a great influence on the Fano resonance. By changing the sensitive parameters, the optimal sensitivity of the refractive index nanosensor is 2280 nm/RIU, and the coefficient of excellence (FOM) is 76.7. In addition, the proposed high-sensitivity nanosensor will be used to detect hemoglobin concentration in blood, which has positive applications for biosensors and has great potential for future nanosensing and optical integration systems.

In this article, a refractive index sensor based on Fano resonance, which is generated by the coupling of a metal–insulator–metal (MIM) waveguide structure and a toroidal cavity with a built-in elliptical ring (TCER) structure, is presented. The finite element method (FEM) was employed to analyze the propagation characteristics of the integral structure. The effects of refractive index and different geometric parameters of the structure on the sensing characteristics were evaluated. The maximum sensitivity was 2220 nm/RIU with a figure of merit (FOM) of 58.7, which is the best performance level that the designed structure could achieve. Moreover, due to its high sensitivity and simple structure, the refractive index sensor can be applied in the field of temperature detection, and its sensitivity is calculated to be 1.187 nm/℃.

A high-property plasma resonance-sensor structure consisting of two metal-insulator-metal (MIM) waveguides coupled with a transverse ladder-shaped nano-cavity (TLSNC) is designed based on surface plasmon polaritons. Its transmission characteristics are analyzed using multimode interference coupling mode theory (MICMT), and are simulated using finite element analysis (FEA). Meanwhile, the influence of different structural arguments on the performance of the structure is investigated. This study shows that the system presents four high-quality formants in the transmission spectrum. The highest sensitivity is 3000 nm/RIU with a high FOM^* of 9.7 × 10⁵. In addition, the proposed structure could act as a biosensor to detect the concentrations of sodium ions (Na⁺), potassium ions (K⁺), and the glucose solution with maximum sensitivities of 0.45, 0.625 and 5.5 nm/mgdL⁻¹, respectively. Compared with other structures, the designed system has the advantages of a simple construction, a wide working band range, high reliability and easy nano-scale integration, providing a high-performance cavity choice for refractive index sensing and biosensing devices based on surface plasmons.