Flexible piezoelectric nanogenerators (PENGs) used in body movement real-time monitoring are of great interest for their wide application potential such as in the field of smart healthcare. In this work, a self-powered BaTiO₃/Polydimethylsiloxane (PDMS) PENG for body movement sensing was successfully fabricated by extrusion 3D printing. Matrix system composed of different ratios of PDMS was selected based on the rheological property of materials. Experimental investigations were conducted to examine the impact of printing pressure and speed on the linewidth. Subsequently, the extrusion parameters for nanogenerators were determined based on the printed linewidth. The composite showed good ferroelectric property. After polarization, the nanogenerators exhibited an improvement in output performance of up to 55.2%. Additionally, the device demonstrated a good linear relationship between voltage and tapped force test by an electromechanical vibrator. Successful detection of body or muscle movement signals was achieved when the nanogenerator was mounted on the human finger, throat, or foot using a wearable sock, highlighting its potential for applications in self-powered wearable devices for smart healthcare.

The dimensions of material extrusion 3D printing filaments play a pivotal role in determining processing resolution and efficiency and are influenced by processing parameters. This study focuses on four key process parameters, namely, nozzle diameter, nondimensional nozzle height, extrusion pressure, and printing speed. The design of experiment was carried out to determine the impact of various factors and interaction effects on filament width and height through variance analysis. Five machine learning models (support vector regression, backpropagation neural network, decision tree, random forest, and K-nearest neighbor) were built to predict the geometric dimension of filaments. The models exhibited good predictive performance. The coefficients of determination of the backpropagation neural network model for predicting line width and line height were 0.9025 and 0.9604, respectively. The effect of various process parameters on the geometric morphology based on the established prediction model was also studied. The order of influence on line width and height, ranked from highest to lowest, was as follows: nozzle diameter, printing speed, extrusion pressure, and nondimensional nozzle height. Different nondimensional nozzle height settings may cause the extruded material to be stretched or squeezed. The material being in a stretched state leads to a thin filament, and the regularity of processing parameters on the geometric size is not strong. Meanwhile, the nozzle diameter exhibits a significant impact on dimensions when the material is in a squeezing state. Thus, this study can be used to predict the size of printing filament structures, guide the selection of printing parameters, and determine the size of 3D printing layers.

The tissue engineering technology provides a new way to solve bone defect. Porous scaffolds supply support and adhesion space for cells. Design of pore structure of scaffolds is one of the key points in tissue engineering scaffolds, because the structure affects the performance of scaffolds directly. In this paper, mechanical properties of square porous Ti6Al4V scaffolds are studied. By finite element simulation, it can be found that the support structure in vertical direction assumes main force, so the structure can be optimized through relative density mapping (RDM) method. The modified arch structures can improve bearing effect of structure with the same porosity. The designed structures are obtained by selective laser melting. Results of compressive strength indicate that the compressive strength decreases with the increase of porosity. When the porosity is between 40% and 60%, the error of compressive strength calculated by Gibson–Ashby model is below 8%. Moreover, the optimized structure clears a better bearing effect, and the bearing capacity can be increased by 20%–30% under the same porosity.

The regeneration of bone and the repair of large segmental bone defects represent critical challenges in regenerative medicine. Natural bone tissue is an anisotropic material characterized by an intricate gradient distribution in structure, mechanical properties, and biochemical composition; this multi-dimensional heterogeneity is crucial for maintaining its physiological functions and guiding regeneration. Although tissue engineering scaffolds have demonstrated significant potential in the treatment of bone defects, homogeneous or single-gradient scaffolds often struggle to precisely recapitulate the high degree of heterogeneity and anisotropy of natural bone from the macroscopic to the microscopic level, thereby limiting their capability in repairing complex bone defects. In recent years, biomimetic gradient scaffolds—particularly those employing multi-gradient synergistic designs that integrate physical structure, biochemical composition, and mechanical properties—have emerged as a research frontier in this field due to their ability to accurately mimic the natural bone microenvironment and regulate cellular behavior. This research aims to systematically review the latest research progress in gradient scaffolds for bone tissue engineering. First, gradient characteristics of biomimetic gradient bone scaffolds are summarized; second, the design strategies for gradient scaffolds are discussed in depth, with a focus on the applications and advantages of advanced fabrication techniques, such as additive manufacturing, in constructing multi-dimensional gradient structures; finally, based on current research findings, the emerging development trends and future research directions of biomimetic gradient bone scaffolds are outlined to provide a reference for innovative breakthroughs in the field of bone tissue engineering.

Touch sensors play a pivotal role in the domain of human-machine interfaces. To streamline the complexity of array electrodes, this paper presents a novel functional gradient piezoelectric composite nanogenerator touch sensor by utilizing only a pair of electrodes for touch position detection through voltage measurements. The rheological characteristics of the BaTiO₃/PDMS composites were evaluated, and the functional gradient nanogenerator was successfully fabricated by extrusion 3D printing. Finite element simulations revealed a significant concentration of stress in the vicinity of the touch position, which gradually diminished farther away. The output voltage demonstrated substantial variation across different touch positions, which was validated by experimental results exhibiting a similar trend. Comparing voltage values enabled the distinction of touch positions, as confirmed by both simulation and experimental findings. The nanogenerator can realize the function of human-machine interfaces.