Background: A pneumatic paediatric ventricular assist device developed at the Foundation of Cardiac Surgery Development, Zabrze, equipped with valves based on J. Moll’s design, with later modifications introduced at the Institute of Turbomachinery, Lodz University of Technology, was tested numerically and experimentally. The main aim of those investigations was to detect stagnation zones within the ventricular assist device and indicate advantages and limitations of both approaches. Methods: In the numerical transient test, a motion of the diaphragm and discs was simulated. Two different methods were used to illustrate stagnation zones in the ventricular assist device. The flow pattern inside the chamber was represented by velocity contours and vectors to validate the results using images obtained in the laser particle image velocimetry experiment. Results: The experimental light-based method implied problems with proper illumination of regions in the wall vicinity. High-resolution flow data and other important parameters as stagnation regions or flow patterns in regions not accessible for light in the particle image velocimetry method are derived in the numerical solution. However, computations of a single case are much more time-consuming if compared to a single experiment conducted on a well-calibrated stand. Conclusion: The resulting main vortexes in the central part of the pump chamber and the velocity magnitudes are correlated in both methods, which are complementary and when used together offer better insight into the flow structure inside the ventricular assist device and enable a deeper analysis of the results.

Background: This study investigated flow analysis inside pediatric ventricle assist devices (VADs) designed and manufactured at the Foundation for Cardiac Surgery Development (FRK), Zabrze, Poland. The main goal of the experiment was to define the minimal heart rate admissible in clinical practice. Methods: The flow was directed by mechanical, single-disc valves developed at the Lodz University of Technology, Institute of Turbomachinery in Lodz, Poland. VAD operation conditions under different heart rates were analyzed. Measurements were performed on Religa PED pediatric VADs (45 cm³ and 30 cm³) with a particle image velocimetry (PIV) system. Results: Due to the PIV method used, the measurements were made without interference of the measuring system onto the flow structure in the investigated channel, as the measurement procedure is noninvasive. During the investigations conducted in different measurement planes, the majority of the flow volume in the chamber was observable. Conclusions: The measurements at different heart rates demonstrated a significant influence of this parameter on the flow nature in the heart ventricle. Additionally, it was found that the heart rate affected the operation of heart valves in the VAD.

Introduction: A constant growth in the population suffering from osteoporotic vertebral weakening is observed. As a result, vertebroplasty procedures become more and more common. Unfortunately, they may be associated with several complications occurring during bone cement injection, including its leakage or overheating of tissues. Despite several experimental studies, there is a lack of data related to random aeration of the bone cement. Therefore, the main objective of the following investigations was to emphasize that random aeration of the bone cement, and, consequently, a compressibility factor, could not be treated as a negligible factor during the vertebroplasty procedure and had to be taken into account in the development of the mathematical model. Materials and methods: A special test rig to reproduce the vertebroplasty procedure was designed and built. The authors conducted numerous experiments on polymethylmethacrylate-based bone cement flows, analyzing different flow conditions, such as volume flow rate and flow channel diameter. Time periods of the flow front between characteristic sections and pressures (differential and gauge) were measured. Results: All investigations revealed that bone cements mixed in special mixing kits were characterized by a random level of aeration which led to varied flow parameters. Comparing the experimental results with the theoretical values of the continuity equation, the highest difference in the flow duration reached 140%. Discussion: It has been proven that the aeration of the bone cement alters the flow dynamics. Therefore, much more data are required for statistical analysis to validate a mathematical model of the bone cement flow.

The development of collagen-based composite materials offers new opportunities for designing bioactive porous structures with tunable properties. This study focuses on sponges or scaffolds fabricated from fish skin-derived tropocollagen combined with detonation nanodiamonds (NDs), aiming to explore how incorporation of NDs and application of radiation, as a potential sterilization method, influence structural and functional characteristics of the material. Freeze-dry methods of sponge fabrication resulted in a bilayered structure of open porosity, with microporosity at the top and a microchannel at the lower part of the material. The sponges demonstrated mechanical properties with relatively low elongation of below 10%, while the maximum stress was reduced by ca. 20% due to irradiation. Hydration and absorption experiments, mimicking the resorption of collagen in physiological conditions of expected application as wound dressing material, demonstrated controllable fluid uptake and gradual material dissolution, taking place over several hours, depending essentially on the irradiation treatment and morphological characteristics of the sponge. These findings highlight the versatility of collagen–nanodiamond composites as platforms, in which structural design and processing parameters control performance. Moreover, they provide a strong indication of the expected behavior of collagen–nanoparticle systems, including those incorporating NDs modified to impart specific biological functionality, such as antimicrobial activity.