Copper nanowires (CuNWs) are a key building block to facilitate carrier conduction across a broad range of nanodevices. For integration into nanoscale devices, manipulation and welding of these nanowires need to be overcome. Based on high energy density laser processing investigation, we report on innovative welding of single CuNWs to a silver film using a tightly focused laser beam combined with manipulation of CuNWs through the dielectrophoresis (DEP) method. Two types of lasers, femtosecond (FS) and continuous-wave (CW), were employed to analyze, improve, and control Cu-NW melting characteristics under high energy density irradiation. The FS laser welding of CuNWs resulted in a metallic joint with a low contact resistance suitable for functional electronic nanodevices. Computational simulations using the 1-D heat diffusion equation and finite difference method (FDM) were performed to gain an insight into metal–laser interactions for high performance welded contact development. Simulation studies on lasers established contrasting melting behavior of metal under laser irradiation. The device feasibility of CuNW based welded contacts was evaluated in terms of the electrical performance of a glucose sensor. It was possible to sense glucose concentration down to 10⁻⁶ M, demonstrating a path towards integration of CuNWs into wearable, flexible nanoelectronic devices.

The additive noise in the condition monitoring system using fiber Bragg grating (FBG) sensors, including white Gaussian noise and multifrequency interference, has a significantly negative influence on the fault diagnosis of rotating machinery. Spectral subtraction (SS) is an effective method for handling white Gaussian noise. However, the SS method exhibits poor performance in eliminating multifrequency interference because estimating the noise spectrum accurately is difficult, and it significantly weakens the useful information components in measured signals. In this study, an improved spectral subtraction (ISS) method is proposed to enhance its denoising performance. In the ISS method, a reference noise signal measured by the same sensing system without working loads is considered the estimated noise, the same sliding window is used to divide the power spectrums of the measured and reference noise signals into multiple frequency bands, and the formula of spectral subtraction in the standard SS method is modified. A simulation analysis and an experiment are executed by using simulated signals and establishing a vibration test rig based on the FBG sensor, respectively. The statistical results demonstrate the effectiveness and feasibility of the ISS method in simultaneously eliminating white Gaussian noise and multifrequency interference while well maintaining the useful information components.

Micro-vibration measurement is crucial for fault diagnosis of robot joints. An increasing number of fiber Bragg grating (FBG) vibration sensors have been developed based on different sensing principles. However, these FBG vibration sensors cannot be applied to high-frequency vibration measurement or embedded into robot joints due to their low resonant frequency, narrow working frequency band, and large size. In this paper, a novel compact high-sensitivity FBG sensor is proposed to measure dynamic strain variations induced by micro-vibrations of robot joints. In the FBG sensor, a sensitization structure is designed, and an FBG is pasted on the sensitization structure by the two-point encapsulation method. When installing the FBG sensor onto an object, thin silicone rubbers are used to reduce the effect of the dynamic strain variation on two support components of the sensitization structure. To improve its measurement performance, the sensitization structure is optimized by response surface methodology and non-dominated sorting genetic algorithm. A vibration response experiment is executed by establishing a vibration test rig, which demonstrates that the FBG sensor has a resonant frequency of 10 kHz, a working frequency band of 50 Hz - 9 kHz, and a great linear response characteristic. Furthermore, after establishing a condition monitoring system of robot joints, the practicability and effectiveness of the FBG sensor for micro-vibration measurement of robot joints are demonstrated. The FBG sensor has the following advantages: compact structure, uniform stress distribution, high resonant frequency, wide working frequency band, strong embeddability, and great dynamic strain amplification capability.