Biomimetics deals with the application of nature‐made
"design solutions" to the realm of engineering. In this
context, mimicking biological materials with fine‐tuned
mechanical properties has been on the agenda of
engineering research and development for many years.
The premise of biomimetics is that it is possible to
reduce diversity and complexity of biological materials
to a number of 'universal' functioning principles. This
requires foremost a deep understanding of the
hierarchical structure of biological materials. It now
appears that multi‐scale mechanics may hold the key to
such an understanding of "building plans" inherent to
entire classes of material.
Based on various physical‐chemical and mechanical
experiments, our focus is the development of multi‐
scale mechanical models. These models mathematically
and computationally quantify how basic building blocks
of biological materials (such as hydroxyapatite
minerals, collagen, and water in all bones found
throughout the vertebrate kingdom) govern the
materials' mechanical properties at different length
scales, from a few nanometers to macroscopic scales.
Thereby, multi‐scale homogenization theory allows us,
at each scale, to identify material representations that
are as simple as possible; but as complex as necessary
for reliable computational predictions of key material
properties, such as poro‐elasticity, creep, and strength.
This can be seen as "reverse" biomimetics engineering:
(civil) engineering methods are used to understand
One of our key findings is that bone's mechanical properties are governed by porous polycrystals which the minerals build up as structural complement to the collagen fibrils found in all connective tissues (also in tendon, cartilage, skin). These polycrystals are not only central to the magnitude of elastic anisotropy of bone materials; but also to their tensile-to-compressive strength ratio that results from universal failure characteristics of differently oriented submicron‐sized mineral platelets. The perspective thus offered by micro‐ mechanics has opened, for the first time, a theoretical understanding of bone mechanics, which is consistent with all major experimental observations. The developed tools have also driven forward our understanding of hierarchical materials with deep roots in Civil Engineering: wood and concrete. Indeed, there are interesting similarities between the failure of extrafibrillar minerals and that of cement hydration products.
Experimentally validated multi‐scale models for hierarchical materials emerge as central design tools for tailoring material composition and morphology that fulfill functional requirements (e.g. minimization of failure risk). This is true for classical civil engineering problems (e.g. shotcrete tunneling); but even more so for the rapidly growing field of regenerative medicine, where biomimetic tissue engineering scaffolds are implanted for tissue regeneration. At the same time, such models open new avenues for the interpretation of state‐of‐the‐art imaging techniques such as (Micro) Computer Tomography.
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J., "Mechanical behavior of hydroxyapatite
biomaterials: an experimentally validated
micromechanical model for elasticity and strength",
J. Biomed. Mater. Res. 88A, 149‐161, 2009.
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"Micromechanics‐based conversion of CT data into
anisotropic elasticity tensors, applied to FE
simulations of a human mandible", Ann. Biomed.
Eng. 36(1), 108‐122, 2008.
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microviscoelasticity model for aging basic
creep of early‐age concrete", J. Eng. Mech.
135(4), 307‐323, 2009.
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V., Renghini, C., Vitale‐Brovarone, C.,
Rustichelli F., Hellmich C., "Micromechanics
of bone tissue engineering scaffolds, based
on resolution error‐cleared computer
tomography", Biomaterials 30, 2411‐2419,