Structural and Biological Materials

1. Structural and Biological Materials By: Albert Ho Ivan Victoria Xinhe Chen Colin Ng

2. Abstract Lobster pinchers http://www.mpg.de/262881/zoom.jpg

3. Abstract Nacre in abalone shell http://www.nature.com/ncomms/journal/v2/n2/images/ncomms1172-f1.jpg

4. Introduction • What are structural and biological materials? • Where does the idea originate from? • What functions do they have? • Can they be applied in a useful way day-to-day tasks?

5. What are structural biological materials? • Structural biological materials are those materials that are commonly found in animals. • Examples include such as spider silk and porcupine quills. • They are mainly composed of primary minerals and bipolymers. • They may be extrapolated to function in the real world.

6. Background • The structural biological materials naturally go back much farther than we can measure. • They have formed part of nature, adapting to help the animal which uses them. • It is possible to measure, study, and even try to make such capabilities available on a macro scale.

7. Basic Concepts • The building blocks are primarily minerals and biopolymers (combination) • Main Characteristics • Weak in tension • Weak in compression • Toughness is conferred by the presence of interfacial feature • Friction, hydrogen bonds, chain strengthening, stretching

8. Differences • There are seven characteristics between biological material and synthetic counterparts • Self assembly - These materials are built from the bottom up, than top down • Multi-functionality – components serve more than one purpose • Feathers : flight, camouflage, insulation • Hierarchy – organized scale level confer distinct and translatable properties from one level to the next http://upload.wikimedia.org/wikipedia/commons/thumb/4/48/A_single_white_feather_closeup.jpg/450px-A_single_white_feather_closeup.jpg

9. Differences II 4. Hydration – the properties are highly dependent on the level of water in the structure • Important to mechanical properties • Strength (decreased by hydration) • Toughness (increased by hydration) Interplay of protein and water http://www.fkp.tu-darmstadt.de/media/fkp/profvogel/fkpvogelresearch/fkpVogelProteineImWasser.jpg

10. Differences III 5. Mild synthesis conditions • Most biological materials are fabricated at ambient temperature and pressure, as well as aqueous environment 6. Evolution and environmental constraints • Structures are not necessarily optimized for all properties but are the result of an evolutionary process leading to satisfactory solutions http://ars.els-cdn.com/content/image/1-s2.0-S1359645412007823-gr1.jpg

11. Differences IV 7. Self healing capability • Synthetic material undergo damage and failure in an irreversible manner • Biological materials often have the capability due to vascularity and cells embedded in the structure to reverse the effects of damage by healing Vasculatory system that provides blood for self healing http://esciencenews.com/files/images/201107265180310.jpg

12. Classes of Biological Materials • The structures of biological materials can be divided into two broad classes • Non-mineralized (“soft”) structures – composed of fibrous constituents • Ex. Collagen, keratin, elastin, chitin, lignin, and other biopolymers http://www.nanokeratin.co.il/88317/NanoKeratin--Hair-Spa-Keratin

13. Classes of Biological Materials 2. Mineralized (“hard”) structures, consisting of hierarchically assembled composites of minerals • Hydroxyapatite, calcium carbonate, and amorphous silica http://www.nhm.ac.uk/resources-rx/images/1018/vent_lucinids-50900-1.jpg

14. Tension Unfurling and straightening of polymer chains http://www.cmu.edu/maty/materials/Properties-of-well-defined/brush-macromolecules.html http://www.sciencedirect.com/science/article/pii/S0032591001002984 stretching of the polymer chain backbones

15. Combining the two equations Results in a typical J stress curve http://www.doitpoms.ac.uk/tlplib/bioelasticity/j-shaped-curves.php

16. Basic Principles and Work Performed • For J-shaped stress-curves, the material to get more stiff as more stress is put on to the material . • The material has high elasticity for low stress. • Materials such as Collagen and spider silk have this type of stress-strain curve. K Kendall and K N G Fuller 1987 J. Phys. D: Appl. Phys. 20 1596 • Collagen is one of the body’s most abundant constructing materials • The tension it can withhold is due to many components from various structural levels. A. Gautieri, S. Vesentini, A. Redaelli, M. J. Buehler, Nano Lett. 11, 757 (2011).

17. The Molecular dynamics Computation, atomic force microscopy and small angle x-ray scattering all shows that collagen exhibits the J-shaped stress-curve. • Dried Collagen show a steeper stress curve and breaks more easily. • Spider silk is one of the toughest materials. • It is made of β sheets and nanocrystals. • At lower strain levels, protein strands uncoil. Entropic unfolding follows. And then β sheets stiffen.

18. Even at high strain levels, Hydrogen bonds are the major contributor to β sheet interactions. • A high stack of β sheets may lead to bending and tensile separation between sheets. • The structure of the β sheets allow a ductile file instead of a brittle fracture, which explains the strength of the silk. • In some Soft materials, α helices are transformed to β sheets under stress. • The process is reversible and thus can withstand high stress.

19. Toughness U is the energy per volume absorbed. Maximum stress with cracks and flaws in material http://www.engr.ucr.edu/~david/kisailus.php The helical structure here also contributes greatly to the shrimp's strong outer shell

20. The Abalone shell is made of mesolayers that grow seasonally . Mineral tiles are separated by organic layers. • The shell is able to deflect cracks around the tiles instead of through them. This increases the total length of the crack and increases the energy needed. • For many arthropods, the shell is made of layers of mineralized chitin. • These layers are stacked into a helical structure called the Bouligand arrangement. • The Bouligand arrangement doesn't’t allow cracks to move along a straight line thereby effectively stopping cracks. • Under stress, the chitin fibers can absorb the strain so the fractured region doesn't break off and the region of fracture can be self healed.

21. A bone rarely snaps into two separate pieces with smooth surfaces. The crack is often deflected orthogonally. • The antler bone is has the highest toughness of bones. It has hypermineralized regions that lead to crack deflection and high amounts o f collagen that lead to crack retardation and creates crack bridges. • The graph shows that fracture toughness increases as the crack propagates. • The presence of interfaces help the sea sponge retard crack propagation. • Organic silicate connects the adjacent layers.

22. Lightweight Structures and their Resistance Bending moment M is related to curvature and Inertia Resistance buckling can be improved by increasing I. Bending resistance Increase in t and decrease in R will increase resistance, but it will also increase buckling tendencies. http://biologylair.tumblr.com/post/30999295709/this-plant-of-the-genus-drosera-is-a-carnivorous

23. Plants have hollow patterns that allow them to decrease their weight and prevent bending by resisting flexure stress. • Porcupine quills have a high strength to weight ratio. The cortex surrounds a cellular core that stabilizes the walls under pressure.

24. Bending strength increases linearly with radial distance http://dpshots.com/photo-inspiration/bird-photography.html Since this is a fourth order dependency, decrease in density is dramatic

25. Bird beaks have extremely low densities. The internal structure is made of bony struts connected by membrane. The hollow core core inside the foam further decreases the weight. • Bird feathers have a high stiffness to weight ratio. • The core is filled with a closed-cell foam and the cell walls are also made of foam. This further decreases the density of the structure.

26. Analysis Overall this is a well written paper, here is what we thought of it: Pros: • The paper is written well in a sense that each paragraph has main points that tie into the topic paper • Charts, graphs and equations are imbedded into the article • It lets the reader know how biological materials are linked to each other and the common ground they share • The article is cited correctly; complete with a section for references and notes Cons: • The paper is a bit lengthy for an article and may lose the attention of the reader • Throughout the article, it jumps from topic to topic without good transition • The paper is a bit disorganized and gives too much useless information • The abstract does not represent the content of the paper well

27. How to Improve • First and foremost, the paper needs to be shortened. Make the paper more concise and to the point. Throw out the filler information and just tell the reader the main points they need to know. For example, there was a pretty detailed segment about the shell of an arthropod and what it is made up of biologically. • Topics need to tie into each other. For example: It goes from talking about concepts of engineering to the attention that biological materials have attracted with no real middle ground in between. • Lengthen the abstract a little bit and make it include more information about the paper.

28. It would be nice to have the paper either be really broad or really specific. Either the paper talks about topics that apply to all biological materials and then in other parts it will go on about the silk of a spider web. We believe that a paper should include one or the other. In this situation, I think they should cover less topics but discuss the unique topics such as the webs spiders create or the beaks that birds possess The beak of a toucan bird The silk of a spider web

29. Follow up • The follow up that we believe needs to be done is just the extra research that needs to be done after the article has been published • Perform experiments and tests in the lab • After this further research; create a new and improved paper • In this new paper, include more pictures to keep the reader interested in the article • Along with the charts and graphs; add some tables of experimentation data

30. Further Research • We believe that more research needs to be done • This can be done in more ways than one: there needs to be more research on other scholarly articles so as to strengthen the understanding on the topic so that the writes can go more in depth • Also we think that there needs to be some work done on these biological materials in a lab type of environment. Do not just take in what the article says but maybe test some of the theories that are spoken through experimentation

31. Works Cited • GG Extra. "Spider Silk – The Future of Tennis Strings?" GGT Extra Spider Silk The Future of Tennis Strings Comments. N.p., 9 May 2009. Web. 25 Apr. 2013. • Graham, Rex. "Engineers Discover Why Toucan Beaks Are Models of Lightweight Strength."Engineers Discover Why Toucan Beaks Are Models of Lightweight Strength. N.p., 30 Nov. 2005. Web. 25 Apr. 2013. <http://www.jacobsschool.ucsd.edu/news_events/releases/release.sfe?id=417>. • http://www.sciencedirect.com/science/article/pii/S1359646212003715 • "Hydrogen Bonding." Elsevier: Article Locator. Nicerweb, n.d. Web. 25 Apr. 2013. • "The Biology Lair." The Biology Lair. N.p., n.d. Web. 10 Apr. 2013. <http://biologylair.tumblr.com/post/30999295709/this-plant-of-the-genus-drosera-is-a-carnivorous>.