Efficiently Fabricated Core-Sheath Piezoelectric Sensor Based on PVDF Microfibrillar Bundle.

With the rapid development of information technology (e.g., Internet of Things (IoT) and artificial intelligence (AI)), piezoelectric sensor (i.e., piezoelectric nanogenerator, PENG) receives an increasing number attention in the field of self-powered wearable devices. Taking piezoelectric fiber as an example, it shows promising application for wearable devices owing to its light weight and high flexibility compared with block electronic devices. However, it still remains a challenge to fabricate low-cost and high-performance piezoelectric fiber via a large-scale but efficient method. In this study, via extrusion molding and leaching, a core-sheath piezoelectric sensor is facilely fabricated, whose core and sheath layer are respectively slender steel wire (i.e., electrode) and PVDF microfibrillar bundle (PMB) (i.e., piezoelectric layer). Such piezoelectric sensor shows decent output performance in both pressing (12.3 V) and bending (0.32 V) mode. Meanwhile, it possesses sensitive stress responsiveness when serving for self-powered sensing. Furthermore, such piezoelectric sensors can realize wearable signal transmission and human motion monitoring, showing promising potential for wearable devices in the future. This work proposes a large-scale but efficient method for fabricating high-performance PVDF microfibril based piezoelectric fiber, opening a new pathway to develop self-powered sensors following the concept of polymer "structuring" processing.

Entropy-Dominated Triplet Exciton Emission in Carbon Dots.

Phosphorescence in carbon dots (CDs) from triplet exciton radiative recombination at room temperature has achieved significant advancement. Confinement and nanoconfinement, serving as valuable techniques, are commonly utilized to brighten triplet exciton in CDs, thereby enhancing their phosphorescence. However, a comprehensive and universally applicable physical description of confinement-enhanced phosphorescence is still lacking, despite efforts to understand its underlying nature. In this study, the dominance of entropy is revealed in triplet exciton emission from CDs through the establishment of a microscopic vibration state model. CDs with varying entropy levels are studied, indicating that in a low entropy system, the multi-energy triplet exciton emission in CDs exhibits enhanced brightness, accompanied by a corresponding increase in their lifetimes. The product of lifetime and intensity in CDs serves as a descriptor for their phosphorescence properties. Moreover, an entropy-dependent information variation system based on the CDs is demonstrated. Specifically, in a low-entropy system, information is retained, whereas the corresponding information is erased in a high-entropy system. This work elucidates the underlying physical nature of confinement-enhanced triplet exciton emission, offering a deeper understanding of achieving ultralong phosphorescence in the future.

Intelligent Vehicle Path Tracking Control Method Based on Curvature Optimisation.

In this study, an intelligent vehicle (IV) path tracking control method based on curvature optimisation is proposed to reduce the comprehensive performance conflict of the system. This system conflict is caused by the mutual restriction between the path tracking accuracy and the body stability during the movement of the intelligent automobile. First, the working principle of the new IV path tracking control algorithm is briefly introduced. Then, a three-degrees-of-freedom vehicle dynamics model and a preview error model considering vehicle roll are established. In addition, a path tracking control method based on curvature optimisation is designed to solve the deterioration of vehicle stability even when the path tracking accuracy of the IV is improved. Finally, the effectiveness of the IV path tracking control system is validated through simulations and the Hardware in the Loop (HIL) test with various conditions forms. Results clearly show that the optimisation amplitude of the IV lateral deviation is up to 84.10%, and the stability is improved by approximately 2% under the vx = 10 m/s and ρ = 0.15 m-1 condition; the optimisation amplitude of the lateral deviation is up to 66.80%, and the stability is improved by approximately 4% under the vx = 10 m/s and ρ = 0.2 m-1 condition; the body stability is improved by 20-30% under the vx = 15 m/s and ρ = 0.15 m-1 condition, and the boundary conditions of body stability are triggered. The curvature optimisation controller can effectively improve the tracking accuracy of the fuzzy sliding mode controller. The body stability constraint can also ensure the smooth running of the vehicle in the optimisation process.

Self-Assembled Hexagonal Superparamagnetic Cone Structures for Fabrication of Cell Cluster Arrays.

In this study, we demonstrated that arrays of cell clusters can be fabricated by self-assembled hexagonal superparamagnetic cone structures. When a strong out-of-plane magnetic field was applied to the ferrofluid on a glass substrate, it will induce the magnetic poles on the upper/lower surfaces of the continuous ferrofluid to increase the magnetostatic energy. The ferrofluid will then experience hydrodynamic instability and be split into small droplets with cone structures because of the compromising surface tension energy and magnetostatic energy to minimize the system's total energy. Furthermore, the ferrofluid cones were orderly self-assembled into hexagonal arrays to reach the lowest energy state. After dehydration of these liquid cones to form solid cones, polydimethylsiloxane was cast to fix the arrangement of hexagonal superparamagnetic cone structures and prevent the leakage of magnetic nanoparticles. The U-343 human neuronal glioblastoma cells were labeled with magnetic nanoparticles through endocytosis in co-culture with a ferrofluid. The number of magnetic nanoparticles internalized was (4.2 ± 0.84) × 106 per cell by the cell magnetophoresis analysis. These magnetically labeled cells were attracted and captured by hexagonal superparamagnetic cone structures to form cell cluster arrays. As a function of the solid cone size, the number of cells captured by each hexagonal superparamagnetic cone structure was increased from 48 to 126 under a 2000 G out-of-plane magnetic field. The local magnetic field gradient of the hexagonal superparamagnetic cone was 117.0-140.9 G/mm from the cell magnetophoresis. When an external magnetic field was applied, we observed that the number of protrusions of the cell edge decreased from the fluorescence images. It showed that the local magnetic field gradient caused by the hexagonal superparamagnetic cones restricted the cell growth and migration.

Diamond based photodetectors for solar-blind communication.

High performance solar-blind photodetectors have been fabricated from diamond wafers. The peak responsivity is 13.0 A/W at 222 nm with a dark current of 0.93 nA under 60 V bias. The rise and decay times of the photodetector are about 1.3 µs and 203 µs, respectively. The responsivity and response time of the device are both among the best values ever reported for diamond-based photodetectors. A solar-blind optical communication system has been constructed by employing the diamond photodetector as a signal receiver for the first time. Benefiting from the high spectral selectivity of the diamond photodetector, the communication system has excellent anti-interference ability. The results reported in this paper may pave the way for the future application of diamond-based solar-blind photodetectors in confidential communications.