Multimodal Imaging of Anisotropic Hierarchical Materials
Doktorsavhandling, 2022

The thesis is focused on studying the nanostructure of natural and synthetic hierarchical materials with biological applications, using X-ray scattering imaging and birefringence microscopy. The term "hierarchical materials" is used for structures composed of sub-units organised in different length scales that create the building blocks for the next level.

Hierarchical materials are commonly found in nature, with diverse structures and functionalities. In the first part of this thesis, the nanostructure of mineralised tissue, such as tusk and bone, was the focus. Scanning SAXS, SAXS tensor tomography and birefringence microscopy were used to study the helicoidal structure of narwhal tusk. A high degree of anisotropy was found, in which the dentine and cementum have a very highly organised nanostructure with a preferential orientation along the tusk. However, those two main components differ in the deviations from that primary orientation, which revealed a complex helical pattern that could be the source of its anisotropic mechanical properties. A layered structure was also observed using X-ray fluorescence spectroscopy, indicating tusk growth layers that reflect the animal history. Those methods were also applied to study the anisotropic nanostructure of regenerated bone in biodegradable scaffolds and titanium implants in vivo, successfully demonstrating that the scaffold or implant architecture influence the new bone formation. Scaffolds with aligned fibres led to well-structured bone and a faster regeneration process, while scaffolds with randomly oriented fibres only created a callus around the damaged area with poor growth of new tissue.

In the second part of this thesis, the anisotropy of self-assembled lyotropic liquid crystals for 3D printing of bone-mimetic composites was studied. This work aimed to understand the fundamental processes and mechanisms that induce the alignment of the self-assembled crystalline units to create composites with more anisotropic mechanical properties. In that study, an in situ characterisation of the nanostructure during flow in the 3D printer was done using scanning SAXS and birefringence microscopy to correlate the manufacturing process with the observed structural alignment of the material. The results demonstrated the role of the shear stress in such liquid crystals, highlighting the effect it has on the anisotropy and morphological transitions in the self-assembled structures. The importance of time and environmental conditions during 3D printing is also shown, which may affect the final structure and orientation.

Biomaterials

Hierarchical Materials

Multimodal Imaging

Birefringence

X-Ray Scattering

PJ-salen, Kemigården 1, Chalmers
Opponent: Stuart R. Stock, Northwestern University, Chicago (USA)

Författare

Adrian Rodriguez Palomo

Chalmers, Fysik, Materialfysik

A. Rodriguez-Palomo*, J. Palle*, E. Garde, P. A. Vibe, T. E. K. Christensen, N. K. Wittig, M. R. V. Jørgensen, I. Kantor, M. Burghammer, J. Liu, K. Jakata, P. Cook, J. T. Avaro, C. Appel, L. C. Nielsen, M.-P. H. Jørgensen, M. Liebi, H. Birkedal, Hierarchical structure of narwhal tusk

Den inre strukturen hos många material har en hierarkisk arkitektur i många olika längdskalor. Små byggstenar sätts ihop i större strukturer som blir byggstenar för nästa hierarkiska nivå, från miljarder gånger mindre än en legokloss upp till centimeter eller till och med meter. Det är fallet med många material av naturligt ursprung, vars struktur ofta definierar deras mekaniska, fysikaliska och kemiska egenskaper. Vi använder röntgenstrålning och polariserat ljus för att avbilda den osynliga strukturen hos dessa material på ett sätt som kan hjälpa oss att förstå byggstenarnas arrangemang i 2D och 3D.
 
Ben, tänder och betar är gjorda av organiska fibrer, kollagen och mineralpartiklar, hydroxiapatit. Dessa vävnader är avancerade kompositmaterial skapade av naturen med imponerande egenskaper som framträder genom komplexa hierarkiska strukturer.
 
Att studera sådana naturliga strukturer är relevant inom biologin för att förstå hur de skapas och regenereras. Denna kunskap är även en inspirationskälla för att skapa syntetiska bioinspirerade material med förbättrade egenskaper och nya funktionaliteter.

The internal structure of many materials has a hierarchical architecture at many different length scales. Small building blocks are assembled together in larger structures that become the building blocks of the next hierarchical level, from billions of times smaller than a Lego block up to centimetres or even metres. That is the case with many materials of natural origin, which structure often define their mechanical, physical, and chemical properties. We use X-rays and polarised light to image the invisible structure of those materials in a way that can help us to understand their building blocks' arrangement in 2D and 3D.
 
Bones, teeth, and tusks are made of organic fibres, collagen, and mineral particles, hydroxyapatite. These tissues are advanced composite materials created by nature with impressive properties that emerge through complex hierarchical structures.
 
Studying such natural structures is relevant in biology to understand how they are created and regenerated. This knowledge is also a source of inspiration to create synthetic bio-inspired materials with enhanced properties and new functionalities.

Ämneskategorier

Materialteknik

Fysik

Biologiska vetenskaper

Atom- och molekylfysik och optik

Datorseende och robotik (autonoma system)

Infrastruktur

Chalmers materialanalyslaboratorium

Styrkeområden

Materialvetenskap

ISBN

978-91-7905-687-2

Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 5153

Utgivare

Chalmers

PJ-salen, Kemigården 1, Chalmers

Online

Opponent: Stuart R. Stock, Northwestern University, Chicago (USA)

Mer information

Senast uppdaterat

2023-11-12