Bone and teeth as fibrous biological composites: in situ nano-mechanical investigations

Lead Research Organisation: Queen Mary, University of London
Department Name: Sch of Engineering and Materials Science

Abstract

Man-made composite materials are used extensively in a variety of structures where high strength and stiffness is required as well as low weight. These composites are almost exclusively constructed from a lightweight polymer reinforced with fibres. The fibres have advantages over other geometries as the mechanical properties are excellent in one particular direction, making the fibre anisotropic. The numerous structures existing in nature are optimized through evolutionary processes for a particular mechanical function. Common examples of biological materials with a mechanical role are bone, required for structural integrity in skeletal systems, and teeth, primarily used for chewing and tearing of food. These materials have striking resemblances to man-made composites as fibrous constituents are used as reinforcement in an organic matrix. However, two main differences are apparent in biological composites when compared to synthetic composites. The first is that the reinforcing fibres in biological composites are much smaller than typical fibres used in engineering composites. Decreasing fibre diameter is widely acknowledged to increase strength and utilization of scale effects in nature highlights the optimization processes used. Furthermore, many organizational levels exist in biological composites from the nano-scale level of the reinforcing fibre building blocks up to the large scale architectures. This structural hierarchy is currently far more complex than any synthetic composite.Understanding how the nano-scale fibre building blocks influence the overall mechanical properties of the biological composite is experimentally challenging due to the structural hierarchy and small size of the fibre reinforcements. Mechanical tests on large samples give results that are difficult to interpret because of the various different fibre organizations. Therefore, testing on the individual nano-scale fibre reinforcements in biological composites would give fundamental information and help to understand how materials like bone and teeth are optimized for their mechanical functions. In addition, the understanding of biological composites at the nano-scale could provide a pathway for developing new synthetic composites with nano-material reinforcements.The project will test samples of bovine bone femur and limpet teeth, which are representative of many different types of bone and teeth found in nature. The nano-scale fibres will be mechanical tested by pulling at the ends of these fibres. The pulling will be done by a scanning probe microscopy, which is ideal for measuring the very small forces needed to deform and break the nano-scale fibres. An electron microscope will also be used to visualize these tests and observe if the nano-scale fibres are fractured during the pulling process or slide out of the surrounding organic matrix. Mechanical models used in conventional composite theory will be applied to assess the mechanical properties of the reinforcing nano-fibres and the surrounding organic matrix. The results of this research will therefore provide unique insight into how natural materials have remarkable mechanical properties from using nano-scale building blocks.

Publications


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Hang F (2011) Nano-mechanical properties of individual mineralized collagen fibrils from bone tissue. in Journal of the Royal Society, Interface
Jimenez-Palomar I (2012) Influence of SEM vacuum on bone micromechanics using in situ AFM. in Journal of the mechanical behavior of biomedical materials
Lu D (2012) Optimized nanoscale composite behaviour in limpet teeth. in Journal of the Royal Society, Interface
Stachewicz U (2011) Enhanced wetting behavior at electrospun polyamide nanofiber surfaces. in Langmuir : the ACS journal of surfaces and colloids
 
Description The first discovery was the development of a technique able to test the mechanical properties of nano fibrous materials from biological structures. Biological structures have optimised mechanical properties, which are a product of the assembly of smaller nano fibrous building blocks to produce structures such as teeth and bone. Understanding the mechanical properties of nano fibrous materials therefore allows us to understand the origin of mechanical behaviour in biological structures.
Exploitation Route Firstly, the techniques developed to measure mechanical properties at small length scales are generic and can be applied to a range of new nano materials. Secondly, the biological structures examined are optimised and provide design principles for synthetic composite materials, such as used in aerospace and the automotive industries. As biology uses sustainable materials that often have poor mechanical properties, the assembly of relatively poorly performing materials to give a structure with outstanding mechanical properties is an important design principle that can be used for future recyclable materials.
Sectors Aerospace, Defence and Marine,Education,Healthcare,Manufacturing, including Industrial Biotechology,Transport
URL http://www.barberresearch.com
 
Description The research progressed understanding of the mechanical properties of teeth from sea creatures and bone using advanced microscopy techniques. The understanding of bone was useful in considering the design of tough materials and led to collaborations with the Ministry of Defence on novel armour. The measurement techniques developed in the research have been applied to understand the behaviour of nanofibres with liquids, supported by defence (DSTL( contracts that seek to develop textiles that repel chemical warfare agents, as well as understand the binding of toothpaste to teeth, supported by GlaxoSmithKlein (GSK).
First Year Of Impact 2009
Sector Aerospace, Defence and Marine,Education,Healthcare
Impact Types Societal
 
Description Electrospinning for liquid control surfaces and understanding of liquid surfaces interactions
Amount £117,884 (GBP)
Funding ID DSTLX-1000072482 
Organisation Defence Science & Technology Laboratory (DSTL) 
Sector Public
Country United Kingdom of Great Britain & Northern Ireland (UK)
Start 08/2012 
End 08/2013
 
Description Electrospinning for liquid control surfaces and understanding of liquid surfaces interactions
Amount £117,884 (GBP)
Funding ID DSTLX-1000072482 
Organisation Defence Science & Technology Laboratory (DSTL) 
Sector Public
Country United Kingdom of Great Britain & Northern Ireland (UK)
Start 08/2012 
End 08/2013
 
Description Queen Mary, University of London
Amount £22,472 (GBP)
Funding ID FEI UK Limited Grant Support 
Organisation Queen Mary University of London (QMUL) 
Sector Academic/University
Country United Kingdom of Great Britain & Northern Ireland (UK)
Start  
 
Description Queen Mary, University of London
Amount £146,677 (GBP)
Funding ID EP/F019882/1 
Organisation Queen Mary University of London (QMUL) 
Sector Academic/University
Country United Kingdom of Great Britain & Northern Ireland (UK)
Start  
 
Description Queen Mary, University of London
Amount £4,797 (GBP)
Funding ID KTA scheme scholarship (internal university fund) 
Organisation Queen Mary University of London (QMUL) 
Sector Academic/University
Country United Kingdom of Great Britain & Northern Ireland (UK)
Start  
 
Description Queen Mary, University of London
Amount £9,089 (GBP)
Funding ID Internal University Award 
Organisation Queen Mary University of London (QMUL) 
Sector Academic/University
Country United Kingdom of Great Britain & Northern Ireland (UK)
Start  
 
Description Keynote talk on nanoscale toughness 
Form Of Engagement Activity Scientific meeting (conference/symposium etc.)
Part Of Official Scheme? No
Geographic Reach International
Primary Audience
Results and Impact Keynote talk on nanoscale toughness delivered to the EU workshop 'Nanotough' in Denmark.
Year(s) Of Engagement Activity 2012
 
Description MRS invited talk on individual collagen fibril nano-mechanics 
Form Of Engagement Activity Scientific meeting (conference/symposium etc.)
Part Of Official Scheme? No
Primary Audience
Results and Impact Invited talk at the MRS Spring Meeting in San Francisco.
Year(s) Of Engagement Activity 2009
 
Description Nano Knowledge Transfer Network Keynote Talk 
Form Of Engagement Activity Scientific meeting (conference/symposium etc.)
Part Of Official Scheme? No
Geographic Reach International
Primary Audience
Results and Impact Keynote talk at KTN on mechanics and surface properties of nano fibres.
Year(s) Of Engagement Activity 2011