No abstract

A flexible triboelectric nanogenerator (TENG) is an indispensable part in future flexible self‐powered system. However, it is still a great challenge to establish a balance among the robust mechanical property, strong triboelectrification effect, and high conductivity of electrode materials. A flexible and enhanced‐performance TENG based on cellulose nanofibrils (CNFs)/transition metal carbides and nitrides (MXene) composite films is developed here for harvesting human movement energy. By introducing CNFs, the mechanical strength, flexibility of the composite film, and sensitive to the temperature change and strain are improved. The effect of CNFs concentration, working force, and frequency on the output performance of TENG is also demonstrated. At the optimized CNFs/MXene ratio of 2/5, the transferred charges and output voltage reach the maximum value of 7.4 nC and 24.9 V, respectively. The maximum instantaneous output power density of the as‐prepared TENG is 1.2 mW m−2. Moreover, a self‐powered flexible display system is demonstrated by integrating the TENG with a flexible alternating current electroluminescence. The flexible TENG based on cellulose nanofibrils‐reinforced MXene composite film is promising as a flexible energy source for self‐powered system.

Wearable electronics or epidermal electronics have attracted growing interest for their expansion into markets as health monitors and for biological applications. However, a key obstacle lies in the light source and the optical path change caused by the deformation and displacement in the measurement. In this work, we demonstrated a wearable and biocompatible blood oxygen monitor by using heterogeneously integrated vertical cavity surface emitting lasers (VCSELs) and a Si photodetector (PD) on a Au-laser-inducedgraphene hybrid electrode. The strategy for fabricating a flexible electrode provides advantages including large-scale fabrication, high cost performance, and simple operation. The full widths at halfmaximum of the 680 and 808 nm VCSEL were 1.8 and 0.8 nm, respectively, which is useful to improve sensitivity. Then, the rigid optoelectronics including narrowband VCSELs and a thinned Si PD were heterogeneously integrated on the flexible electrodes. Owing to the great flexibility and excellent light source, the wearable device conformal to the skin's surface can be utilized to extract blood oxygen (SpO 2 ). It was successfully demonstrated that the flexible device can extract the photoplethysmography signals of various regions including the fingernail, the wrist, and the earlobe. This work proposes an alternative strategy to miniaturizing an integrated device for long-life and continuous medical monitoring.

The flexible self-powered display system integrating a flexible triboelectric nanogenerator (TENG) and flexible alternating current electroluminescence (ACEL) has attracted increasing attention for its promising potential in human–machine interaction applications. In this work, a performance-enhanced MXene/cellulose nanofibril (CNF)/MXene-based TENG (MCM-TENG) is reported for powering a flexible patterned ACEL device in order to realize self-powered display. The MCM multilayer composite film was self-assembled through the layer-by-layer method. The MCM film concurrently acted as a triboelectric layer and electrode layer due to its high conductivity and strength. Moreover, the effect of CNF concentration and number of layers on the output performance of TENG was investigated. It was found that the MCM-TENG realized the optimum output performance. Finally, a flexible self-powered display device was realized by integrating the flexible TENG and ACEL. The MCM-TENG with an output voltage of ≈90 V at a frequency of 2 Hz was found to be efficient enough to power the ACEL device. Therefore, the as-fabricated flexible TENG demonstrates a promising potential in terms of self-powered displays and human–machine interaction.

Ceramic matrix composites (CMCs) with carbon fiber reinforcement are widely used in the aircraft industry and other important defense industries due to their superior performance. To investigate the factors affecting the grinding force and surface quality of 2.5D needled Cf/SiC material, the motion equation of abrasive particles under longitudinaltorsional ultrasonic vibration was established using kinematic analysis, and the trajectory analysis of abrasive particles was carried out using MATLAB simulation. The grinding force, surface topography, and roughness of conventional grinding (CG) and longitudinal-torsional ultrasonic vibration-assisted grinding (L-TUVAG) were analyzed and evaluated to explore the process mechanism of Cf/SiC material damage. An improved processing technique and parameters for processing were proposed. The findings show that the principal pathways for material removal during grinding are matrix breaks, interfacial debonding, fiber damage, and fractures. Grinding parameters have a significant influence on the quality of the processing surface. The surface topography steadily improves during the grinding process as the grinding wheel speed increases. However, the feed speed and grinding depth have a reverse impact. High-speed micro-grinding can significantly improve grinding efficiency and surface processing quality. L-TUVAG has a lower grinding force than CG by a factor of 16.16% to 35.82%, and the surface processing quality is correspondingly better. These discoveries enable the prediction of surface morphology and roughness characteristics of materials. And provide important technological support for improving the processing quality of CMCs.