Biomedical Engineering Reference
In-Depth Information
11.6 Conclusions and perspectives
Biodegradable implants show great potential in many areas of medicine, but this
technology has been hampered by the lack of reliable models to predict the behaviour
and evolution of biodegradable materials. The design of biodegradable implants (a
complex and challenging process) is largely based on designer's intuition and guess-
work with trial-and-error attempts. In order to advance from prototype status to re-
liable human-implantable devices, a very resource-expensive product development
process of several in vivo and in vitro iterations that often fail must be taken. A prime
example of this failure is the fact that the concept pof biodegradable vascular stents
dates back to the 1980s, yet there are no FDA or CE approved designs on the market
today [32].
The application of multiscale computational models has been proved to be an
effective and promising tool for the study of biodegradable polymers and for the de-
sign of biodegradable implants. On the one hand, molecular dynamics simulations
provide a self-consistent method to quantify the constitutive laws that characterize
the behaviour of such complex materials, and in particular, the diffusion of certain
species in polymeric mixtures. On the other hand, continuum based models with its
associated established and efficient numerical methods are the natural test bed for
optimized computational design of biodegradable implants. The incorporation of de-
scriptions of material behaviour at the molecular level into account at the constitu-
tive specification of the response of the material at the continuum level represents the
connection between both scales of the multiscale model, and, if fully accomplished,
certainly provides a superior understanding and predictability of biodegradable ma-
terial behaviour.
Unequivocally, the present work puts into evidence interesting perspectives for
the interaction of different disciplines such as numerical analysis, computer science
and bioengineering. The final objective of efficiently integrating atomistic simula-
tions with macroscale computational models is still far from being reached, but the
experience gathered with this work suggests that the combination of ad hoc numeri-
cal algorithms with the emerging high performance computational facilities could be
a powerful and promising tool to achieve an accurate and reliable investigation of not
only polymer degradation, but also a multitude of other complex phenomena. More
interestingly, as the development of molecular dynamics as a field ensues and bet-
ter descriptions of the behaviour of the material at the molecular level are achieved,
these could supply valuable information about materials with complex and evolv-
ing microstructures (a very large class indeed, and very common within the field of
biomechanics) to macroscale modelling approaches based on the continuum frame-
work.
Acknowledgements.
We acknowledge the Italian Institute of Technology, with the Grant:
Mod-
els and methods for degradable materials
, and the European Research Council Advanced Grant:
Mathcard - Mathematical Modelling and Simulation of the Cardiovascular System
, Project ERC
2008 AdG 227058. JSS thanks the Portuguese Funda¸aoparaaCiencia e Tecnologia for its support,
Grant SFRH/BPD/63119/2009.
