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The Architectured Materials Group aims at developing novel materials that fill desirable white spaces in the Ashby diagrams. We investigate fundamental processes of small scale plasticity under extreme conditions and multiscale toughening mechanisms in complex hierarchical materials. We translate this knowledge into the design of novel metamaterials with hierarchical architecture and tailored microstructure that allow us to combine usually mutually exclusive properties, e.g. high strength and toughness with a low density. To achieve this, we actively develop nanomechanical instruments and methods and closely integrate experimental and modeling approaches.
Fundamental processes of plasticity and failure in microscale components
A potential pathway towards high specific strength materials is to make use of both extrinsic and intrinsic size effects in the design of mechanical metamaterials. We investigate the rate limiting plastic processes at the nanoscale and the effect of grain and component size on the mechanical behaviour through a combination of thermal activation analysis at low temperatures and high strain rates, microstructural analysis, and computational modeling. A thorough understanding of the fundamental deformation mechanisms enables us to find pathways for influencing the mechanical behavior of the material through microstructural design. To achieve this, we push the limits of what can be measured at the microscale today through active instrument and method development, e.g. for mode-dependent fracture, tensile, cryogenic temperature, or high strain rate experiments. (Materials & Design 2020
, JMR 2019
, Nano Letters 2019
, FFEMS 2018
Microtensile experiments as a function of strain rate on specimens prepared by 2 photon lithography (Materials & Design 2020)
Multiscale failure of hierarchical materials
Furthermore, we study the failure of complex materials such as hierarchical biological nanocomposites (e.g. bone, wood, teeth) or nanostructured thin films to identify how these materials manage to combine toughness and strength with a light weight through multiscale toughening mechanisms. We assess the influence of their complex microstructure, i.e. the role of interfaces, defects, and material inhomogeneity, on their macroscopic failure. Combining challenging mechanical experiments, microstructural analysis, and mechanical modeling spanning from the nano- to the macroscale allows us to investigate and model the underlying physical processes in these materials at the relevant length scales. (Acta Biomaterialia 2020, Acta Biomaterialia 2017, Nature Materials 2014)
Study on the deformation and failure mechanisms in lamellar bone through combination of micropillar compression, TEM imaging, and micromechanical modeling (Acta Biomaterialia 2017)
Application to clinical problems in bone biomechanics
We further aim to apply high throughput microscale analysis methods to help solve clinical problems with a societal impact. The rising number of bone fractures poses a challenge to ageing societies worldwide. A large portion of physiological loading is carried by cortical bone which motivates the need to understand its structure-property relationships at several length scales. Together with our partners, we investigate whether micromechanical measurements may be combined with compositional, morphological, and proteome information to predict macroscopic bone strength in a donor- and site-matched manner. This research has the potential to help form a better understanding of the mechanisms of ageing and disease in bone and can lead to an improved personalized fracture risk prediction in the future. (Acta Biomaterialia 2021
, Bone 2016
Combining different microanalysis techniques with morphological and proteomics analysis to answer clinical questions based on data mining approaches.
Design, synthesis, and characterization of hierarchical metamaterials
Based on the gained knowledge on fundamental processes at the nanoscale and multiscale toughening mechanisms, we develop novel materials that feature advantageous combinations of properties such as a high specific strength and toughness through simulation-assisted design. This is achieved by making use of size effects, microstructural design, and hierarchical architecture through a combination of microscale additive manufacturing techniques like two photon lithography, electrodeposition, and atomic layer deposition, to prepare materials that are light, strong and damage resistant and fill desirable white spaces in the Ashby diagrams. (Materials & Design 2020
Nanotomography of a gyroid structure synthesized by combination of 2-photon lithography, elektrodeposition, and atomic layer deposition
Efficient material discovery through a combinatorial approach
We furthermore develop high throughput processes for efficient material discovery based on thin film combinatorial material libraries. These are synthesized by thin film deposition techniques like physical vapor deposition and atomic layer deposition and analyzed in terms of their composition, microstructure, and mechanical performance under various boundary conditions to identify process-composition-structure-property relationships. This allows the effective screening of material libraries to identify materials of interest for specific applications like improved chemical or wear resistance.
Efficient materials discovery through combination of thin film material library synthesis with high throughput experi-mental techniques