The biological characteristics and action mechanisms underlying the excellent performance of skeletal muscles were studied through experiments to provide a scientific basis for the development of flexible actuators with performance comparable to that of skeletal muscles.

A frog skeletal muscle sample was contracted by applying electrical stimulation, and then tensile load was applied to it to analyze the relationship between the driving properties (such as contraction length and output force) of skeletal muscle and its structure from three aspects: skeletal muscle dimensions, tendon, and epimysium.

The contraction lengths of these skeletal muscle samples were approximately 28.92% and 20% under unloaded conditions and under 50% of their maximum output force, respectively. When the load on the skeletal muscles did not exceed 20% of their maximum output force, they also exhibited the property of rapid reduction (approximately 1.25 s). The active tendon increased contraction by approximately 19.68% compared with the inactive tendon, and the integrity of the epimysium protected the force transfer efficiency of skeletal muscles.

By simulating the structural and biomechanical properties of skeletal muscles, flexible actuators can achieve better driving performance, thus greatly promoting the development of bionic robots.

To propose a transfer learning-based method for breath sound feature recognition and autonomous determination of sputum suction timing.

An electronic stethoscope was used to collect breath sounds from the main airways of clinically ventilated patients before and after sputum suction, with pre-suction breath sounds labeled as requiring suction. The collected data underwent high-pass filtering and wavelet soft-threshold denoising, followed by the extraction of log-Mel spectrograms. A VGGish model pretrained on the Audio Set dataset was then employed to extract feature vectors from these spectrograms, which were subsequently classified using a support vector machine to determine whether suction was required.

The precision, recall and F₁ score for recognition of breath sounds requiring sputum suction were 86.73%, 93.06% and 89.78%, respectively.

The proposed breath sound recognition method based on transfer learning effectively determines the timing of sputum suction and shows a significant clinical potential.

To investigate the effects of inclined axial compressive force and flexion moment on the anterior and posterior shear stiffness of the lumbosacral segment.

Six fresh-frozen human cadaveric L5-S1 segments were tested under intact and two progressively impaired structural conditions: intact, a 4-mm bilateral facet joint gap, and anterior discectomy with nucleus pulposus removal plus circumferential release of the inner annular fibers (disc injury). A 300 N axial compressive force was applied either vertically downward or with a 10° or 20° anterior inclination through the disc's shear center. Anterior (0 N to 250 N) and posterior (-50 N to 0 N) shear tests were conducted using a material testing machine. These tests were repeated under a 5 N·m flexion moment. The relative motion between L5 and S1 was measured using a three-dimensional motion capture system.

In the intact state, the inclination of the axial compressive force did not significantly alter anterior or posterior shear stiffness. However, the application of a flexion moment increased anterior shear stiffness by 49.3%. Progressive structural damage resulted in incremental increases in anteroposterior shear translation and corresponding reductions in stiffness. Notably, under combined loading with axial compression and flexion moment, anterior stiffness decreased from 939 N/mm (intact) to 224 N/mm (disc injury), while posterior stiffness decreased from 572 N/mm to 217 N/mm. Within the low-load range, no significant differences in shear stiffness were observed across any structural conditions, regardless of axial force inclination or combined with a flexion moment.

This study supports the clinical view that retro-inclination of the pelvis serves as a compensatory mechanism to enhance segmental shear stability. However, this compensatory capacity gradually diminishes and ultimately fails as spinal degeneration progresses.

To analyze the reverse mechano-electric effect of the layered structure of articular cartilage and its influencing factors.

The cartilage samples were classified according to their physiological thickness (approximately 0.4 mm for the upper layer, 1 mm for the middle layer, and 0.6 mm for the lower layer). Through a non-contact external electric field testing method, how different influencing factors affected the reverse mechano-electric effect of articular cartilage was analyzed.

When the electric field spacing decreased, water content increased, and in vitro time decreased, the displacement of normal layered cartilage in a non-contact electric field increased by 18, 10, 15 μm, respectively. In the case of simulated arthritis defects, as the defect depth and radius increased, the overall deviation deflection of articular cartilage gradually decreased by about 7 μm.

The three-layer cartilage differed in their reverse mechano-electricity effects, showing the greatest deflection in the middle layer at 90% water content, under 7 mm electric field spacing, and after 12 hours ex vivo.

By applying the long short-term memory (LSTM) neural network model and using lower body landmark coordinates obtained from a markerless motion capture system as inputs, to estimate ground reaction force (GRF) curves during running.

The video images and GRF data of 59 amateur runners during running were collected by the markerless motion capture system and three-dimensional (3D) force plates. The LSTM model was established, and the 3D coordinates of 11 lower body landmarks, obtained via the Theia3D markerless system, were used as inputs to estimate the 3D GRF curves during the stance of running. The estimation performance was evaluated using correlation coefficients r, root mean square error (RMSE), and normalized root mean square error (nRMSE) by comparing LSTM model estimation and force plate measurement. Statistical parametric mapping was used to analyze differences in GRF curves estimated by the LSTM model and measured by the force plate, while paired t-tests were used to assess differences in GRF characteristics between model estimation and actual measurement.

A strong correlation (r>0.85, P<0.001) and lower error (RMSE<0.3 body weight, nRMSE<15%) was found between the LSTM model estimation and actual measurements. No significant difference was found in GRF curve intervals between LSTM model estimation and actual measurements. There was no significant difference in GRF characteristics between LSTM model estimation and actual measurements (P>0.05).

Based on the LSTM model, the 3D GRF curves can be effectively estimated by lower body landmark coordinates obtained from the makerless motion capture system, thereby acquiring the highly accurate GRF characteristics. The LSTM model developed in this study can be used to monitor injury risks during running in outdoor environments.

To analyze the effects and differences of two veno-arterial extracorporeal membrane oxygenation (VA-ECMO) cannulation methods and subsequent left ventricular unloading on cardiac function and hemodynamics.

The lumped parameter model (LPM) of VA-ECMO integrated with the cardiovascular system in the MATLAB/Simulink environment was extended to simulate and analyze the changes in ventricular function and blood flow in the heart failure patient model under central VA-ECMO or peripheral VA-ECMO support. The effects of using arterial vasodilators or a left atrial drainage cannula on left ventricular function under central VA-ECMO support at a pump flow rate of 3 L/min were compared.

Under central VA-ECMO or peripheral VA-ECMO support, left ventricular pressure and volume increased, and stroke volume and ventricular work decreased. Both arterial vasodilators and the left atrial drainage cannula could reduce left ventricular pressure and volume. Arterial vasodilators additionally increased stroke volume and improved left ventricular ejection fraction from 11.6% to 19.5%.

Both VA-ECMO cannulation methods provide effective circulatory support in the heart failure patient model, with similar effects on ventricular function. Under central VA-ECMO support, arterial vasodilators can improve left ventricular function more effectively than the left atrial drainage cannula.

To investigate the therapeutic effects of copper-doped barium titanate (BaCuTiO₄) piezoelectric materials combined with low-intensity pulsed ultrasound (LIPUS) to activate their piezoelectric-catalytic synergistic effect for treating implant-associated infections.

BaCuTiO₄ coatings were synthesized on the surface of Ti-6Al-4V substrates using a hydrothermal method, and their surface morphology was characterized by scanning electron microscopy. The piezoelectric characteristics of the coatings were analyzed using a piezoresponse force microscope. An in vitro biofilm model of methicillin-resistant staphylococcus aureus (MRSA) was used, with barium titanate (BaTiO₃) coatings serving as the control group. Under LIPUS intervention (1.0 W/cm², 1 MHz, 10 min), the bacterial viability was assessed using colony counting to evaluate the antibacterial performance of the BaCuTiO₄ coatings. Confocal microscopy was used to observe biofilm viability in different groups, assessing the biofilm removal capability of the coatings. Reactive oxygen species (ROS) generation in each group was detected using Rhodamine b as a probe to evaluate the catalytic efficiency of the coatings in generating ROS.

Copper doping significantly reduced the piezoelectric coefficient of the coating (from 17.7 pm/V to 7.8 pm/V), bringing its piezoelectric performance closer to the requirements of natural bone tissues. Under LIPUS activation, the BaCuTiO₄ coatings increased the generation efficiency of reactive oxygen species by 67.5% and effectively disrupted and removed biofilms formed by MRSA, achieving an antibacterial rate of 90.5%.

The BaCuTiO₄ coatings achieve efficient antibacterial and biofilmclearing functions through a piezoelectric-catalytic synergistic mechanism. Their piezoelectric properties are well-matched with natural bone tissues, promoting implant osseointegration.