Mechanical bone growth stimulation by magnetic fibre networks obtained through a competent finite element technique

Resonance vibration interventions in the femur: Experimental-numerical modelling approaches

MOTIVE

External vibration excitation might be key to many novel non-surgical interventions for pathologies in the musculoskeletal system and in other parts of the human organism. Lack of understanding about vibration patterns, their controllability, and reproducibility are three limitations of ongoing research. This study establishes a bovine vibration model and animal model replacements for future research.

METHODS

We used biological samples (n=5) and one polyurethane sample of the bovine femur. Mechanical resonance was measured experimentally and analysed numerically by finite element method.

MAIN RESULTS

The experiments obtained 5 distinct mode shapes for the biological sample set, with standard deviation < 7.5%. Finite element analysis of the biological samples can replicate experimental mode shape deflection. The use of polyurethane changes resonance character but results are also good approximations of the biological samples.

CONCLUSIONS

A model of the bovine femur with consistent resonance behaviour is presented with alternatives (polyurethane and finite element analysis) that can serve in reducing the number of necessary biological samples. Future work will be to adapt results to human anatomy. Of clinical interest will be to influence bone pathologies such as post-surgical non-union, or bone functionality as part of haematopoiesis and endocrine secretion.

On the quantification of local power densities in a new vibration bioreactor

We investigate the power densities which are obtainable locally in a vibration bioreactor. These reactor systems are of great relevance for research about oncological or antibacterial therapies. Our focus lies on the local liquid pressure caused by resonance vibration in the fluid contained by the reactor's petri dish. We use for the excitation one piezoelectric patch which offer advantages concerning controllability and reproducibility, when compared to ultrasound. The experimental work is extended by finite element analyses of bioreactor details. The peaks of the vibration response for water, sodium chloride (0.1N Standard solution), and McCoy's 5A culture medium are in good alignment. Several natural frequencies can be observed. Local power density can reach multiple times the magnitude used in ultrasound studies. Based on the observed local power densities, we are planning future work for the exposure of cell cultures to mechanical vibration.

Nano-CT scans in the optimisation of purposeful experimental procedures: A study on metallic fibre networks

Motive Metallic fibre networks and their mechanical behaviour are only insufficiently understood. In this particular field of research, the use of nano-CT scans offers advanced opportunities for the optimised planning of experimental work and component design. Several novel applications will benefit from this research; in particular, tissue engineering applications where a controlled and reproducible mechanical stimulus on cells is required can make use of these components. MethodFor the present study, the geometry of metallic fibre network samples is measured and digitalised through the use of nano-CT scan protocols and adequate radiological post-processing steps. Fibre medial axes are transferred into finite element assemblies and are exposed to magnetic actuation models. Network displacement of input geometries is quantified by averaging of node displacement fields. Key resultsComplex 3D deformation fields with regions of tension, shear, and compression are obtained. Results from a previous study about matrix material deformation can be confirmed in this study for greater sample geometries. The strain magnitude is not uniform across the samples; several influencing parameters and deformation patterns are identified. A simple analytical model can be presented which quantifies the material deformation. ConclusionsNano-CT scans provide an efficient radiological tool in the planning of relevant experimental procedures. The present study confirms the general usability of fibre networks for the contactless creation of 3D strain fields in tissue engineering. Mechanical effects in tissue growth stimulation known from experimental work are obtained numerically for the investigated assemblies. Further work about the mechanical effects in tissue cultures appears highly worthwhile.

Experimental and Numerical Design and Evaluation of a Vibration Bioreactor using Piezoelectric Patches

In this present study, we propose a method for exposing biological cells to mechanical vibration. The motive for our research was to design a bioreactor prototype in which in-depth in vitro studies about the influence of vibration on cells and their metabolism can be performed. The therapy of cancer or antibacterial measures are applications of interest. In addition, questions about the reaction of neurons to vibration are still largely unanswered. In our methodology, we used a piezoelectric patch (PZTp) for inducing mechanical vibration to the structure. To control the vibration amplitude, the structure could be excited at different frequency ranges, including resonance and non-resonance conditions. Experimental results show the vibration amplitudes expected for every frequency range tested, as well as the vibration pattern of those excitations. These are essential parameters to quantify the effect of vibration on cell behavior. Furthermore, a numerical model was validated with the experimental results presenting accurate results for the prediction of those parameters. With the calibrated numerical model, we will study in greater depth the effects of different vibration patterns for the abovementioned cell types.