Implantable hydrogel-based bioelectronics (IHB) can precisely monitor human health and diagnose diseases. However, achieving biodegradability, biocompatibility, and high conformality with soft tissues poses significant challenges for IHB. Gelatin is the most suitable candidate for IHB since it is a collagen hydrolysate and a substantial part of the extracellular matrix found naturally in most tissues. This study used 3D printing ultrafine fiber networks with metamaterial design to embed into ultra-low elastic modulus hydrogel to create a novel gelatin-based conductive film (GCF) with mechanical programmability. The regulation of GCF nearly covers soft tissue mechanics, an elastic modulus from 20 to 420 kPa, and a Poisson's ratio from − 0.25 to 0.52. The negative Poisson's ratio promotes conformality with soft tissues to improve the efficiency of biological interfaces. The GCF can monitor heartbeat signals and respiratory rate by determining cardiac deformation due to its high conformability. Notably, the gelatin characteristics of the biodegradable GCF enable the sensor to monitor and support tissue restoration. The GCF metamaterial design offers a unique idea for bioelectronics to develop implantable sensors that integrate monitoring and tissue repair and a customized method for endowing implanted sensors to be highly conformal with soft tissues.

To investigate the effect of initial cracks on the fatigue performance of high-strength bolts for high-speed train brake discs, the fatigue crack propagation behavior of high-strength bolts under the coupling action of preload and dynamic fatigue load was investigated experimentally and numerically based on the theory of linear elastic fracture mechanics. Firstly, fatigue tests of high-strength bolts with initial crack defects were carried out, and then a three-dimensional accurate numerical model with the hexahedral mesh for a bolt-nut was established by MATLAB, and the fatigue crack propagation behaviors were investigated using ABAQUS-FRANC3D interactive technology. In this paper, the effects of the initial crack state, the bolt preload, the axial excitation load, and the friction coefficient of the screw pair on crack propagation life were emphatically studied, and the simulated crack propagation trajectory and crack propagation life agreed well with the experimental results. The findings indicated that 0°-oriented cracks beginning at the maximum principal stress were predicted to have the shortest fatigue life. The crack propagation life was sensitive to the initial crack size, the coefficient of initial crack geometry, and the bolt preload, but not to the friction coefficient of the screw pair. Furthermore, when evaluating the effect of fatigue load on crack propagation, the load ratio, the mean load, and the load range should all be considered.

The development of biomimetic cartilage constructs (BCCs) with natural extracellular matrix (ECM) microenvironments and topological cues to accelerate the reconstruction of natural articular cartilage (NAC) after injury is challenging due to its complex structure, low cellular content, and less vascularity. Inspired by concrete rebar structure, a biomimetic cartilage named “biological reinforced concrete” is fabricated, with collagen fiber orientation transitioning from parallel to perpendicular, replicating the ECM microenvironments and complex construct of NAC. 3D‐printed ultrafine fiber networks (UFNs) served as a degradable “biorebars”, while a hybrid biohydrogel acted as “biocement”. The stem cells are utilized as “bioactive aggregates”. The biocement is developed by combining and screening various biohydrogels to mimic an ECM microenvironment conducive to the formation of NAC. By adjusting the fiber scale and spacing of the UFNs, the mechanical properties of the biomimetic cartilages are controlled to resemble those of NAC. Additionally, the UFNs guided the directed growth of cells and the orderly secretion of ECM. Subsequently, the developed BCCs are implanted into an osteochondral defect, and after 4 months, they successfully reconstructed the complex structure of cartilage with mechanical properties closely resembling those of NAC. The biological reinforced concrete offers a customizable and universal strategy for tissue regeneration.

As the terminal of the power system, the distribution network is the main area where failures occur. In addition, with the integration of distributed generation, the traditional distribution network becomes more complex, rendering the conventional fault location algorithms based on a single power supply obsolete. Therefore, it is necessary to seek a new algorithm to locate the fault of the distributed power distribution network. In existing fault localization algorithms for distribution networks, since there are only two states of line faults, which can usually be represented by 0 and 1, most algorithms use discrete algorithms with this characteristic for iterative optimization. Therefore, this paper combines the advantages of the particle swarm algorithm and genetic algorithm and uses continuous real numbers for iteration to construct a successive particle swarm genetic algorithm (SPSO-GA) different from previous algorithms. The accuracy, speed, and fault tolerance of SPSO-GA, discrete particle swarm Genetic algorithm, and artificial fish swarm algorithm are compared in an IEEE33-node distribution network with the distributed power supply. The simulation results show that the SPSO-GA algorithm has high optimization accuracy and stability for single, double, or triple faults. Furthermore, SPSO-GA has a rapid convergence velocity, requires fewer particles, and can locate the fault segment accurately for the distribution network containing distorted information.

To investigate the fatigue crack propagation behavior of high-strength bolts for high-speed train brake discs, the fatigue crack propagation of high-strength bolts with initial defects under various load ratios was numerically simulated and experimentally verified based on fracture mechanics in this paper. Firstly, the fracture mechanics model of a three-dimensional hexahedral mesh with initial root defects was established using ABAQUS-FRANC3D interactive technology. Then the stress intensity factor (SIF) of the crack front was calculated by the stress superposition of the crack surface to simulate the coupling effect of preload and axial cyclic load. Based on it, fatigue crack propagation was simulated. Finally, the corresponding fatigue experiments on prefabricated crack bolts were carried out. The results show that mode I cracks dominate in the process of crack propagation. The stable crack propagation zones of the fractured high-strength bolts all show a semi-elliptical cross-section. The SIF of the crack front decreases with the increase of the load ratio, thus making the crack propagation life increase with the increase of the load ratio. The experimental outcomes are in great agreement with the simulation results, which verify that the numerical simulation method can effectively and accurately evaluate the fatigue life of high-strength bolts with initial defects and provides an effective means for predicting the fatigue crack propagation life of the same type high-strength bolts in engineering applications.

Tissue-engineered tubular scaffolds (TETS) provide an effective repair solution for human tubular tissue loss and damage caused by congenital defects, disease, or mechanical trauma. However, there are still major challenges to developing TETS with excellent mechanical properties and biocompatibility for human tubular tissue repair. Gelatin-based hydrogels are suitable candidates for tissue-engineered scaffolds because they are hydrolyzed collagen products and have excellent biocompatibility and degradability. However, the mechanical properties of gelatin-based hydrogels are relatively poor and do not align well with the mechanical properties of human tubular tissues. Inspired by the extracellular matrix architecture of human tubular tissues, this study utilizes high-precision 3D printing to fabricate ultrafine fiber network tubular scaffolds (UFNTS) that mimic the arrangement of collagen fibers, which are then embedded in a cell-compatible gelatin-based hydrogel, resulting in the preparation of a fiber/hydrogel biocomposite tubular scaffold (BCTS) with tunable mechanical properties and a J-shaped stress-strain response. Finite element analysis was employed to predict the mechanical behavior of the UFNTS and BCTS. Experimental results indicate that by modifying the structural parameters of the UFNTS, the mechanical properties of the BCTS can be effectively tuned, achieving a programmable range of tensile modulus (0.2–4.35 MPa) and burst pressure (1580–7850 mmHg), which broadly covers the mechanical properties of most human tubular tissues. The design and fabrication of BCTS offer a new approach for the development of TETS while also providing a personalized strategy for such scaffolds in tissue engineering.