斑馬鯊是一種食殼性的底棲鯊魚，以具有堅硬外殼的水中生物為食，例如軟體動物與甲殼動物。此外，斑馬鯊也會吃其他硬骨魚的肉。在食用這兩種不同的獵物時，斑馬鯊魚的牙齒會經由一種特定的機制，重新調整牙齒的角度用於穿刺肉類或用於磨碎貝殼。
為了瞭解這種具有高磨耗性牙齒的食殼性動物，此研究針對斑馬鯊牙齒做化學成分分析，微結構觀察與機械性質的量測。該結果也與尖吻鯖鯊牙齒做比較，該牙齒細長如針，通常用於穿刺獵物。在比較當中，我們可以從中了解不同形貌與功能的牙齒的異同。
結果顯示，此兩種鯊魚牙齒皆由相似的化學成分所組成，並也因此具有相似的機械性質。而在類琺瑯質上，其機械強度皆與海底動物的外殼差異不大。在缺少機械強度的優勢下，斑馬鯊藉由調整牙齒的角度及齒列分布來減低食用貝類所造成的磨損。這兩種鯊魚不同之處在於類琺瑯質束的方向排列，而造成排列不同的原因與捕獵時牙齒內所受應力分佈有關，對於斑馬鯊而言，由於其獨特的獵食機制，其類琺瑯質束的方向排列同時具有用於穿刺與磨碎的特色。為了適應環境並生存，鯊魚牙齒演化出獨特結構與優化之性能。

Zebra sharks are durophagous sharks, which consume the hard-shell bearing prey, such as mollusks and crustaceans. Besides, zebra sharks also feed on bony fish. In feeding on these two types of prey, zebra sharks undergo the teeth reorientation through a unique mechanism for puncturing and grinding. To understand the design strategy of high wear resistance in the durophagous fish, zebra shark teeth were investigated by chemical composition analysis, microstructure characterization, and mechanical property evaluation. The needle-like shortfin mako shark teeth, which were used for puncturing fish prey, were also studied and compared with zebra shark teeth. The results revealed that both sharks were constructed with similar chemical composition; thus, they showed the similar mechanical properties, with the hardness and reduced modulus comparable to that of the conch shell in enameloid. Without the superior mechanical properties, zebra sharks utilize dentition and teeth reorientation to prevent the damage from grinding and wearing during feeding shellfish. The difference between sharks is the orientation and distribution of enameloid bundles, which is be related to the external loading condition during feeding. Zebra shark teeth showed the mixture of the characteristics from puncturing and grinding due to its tunable feeding mechanism. Shark teeth have evolved unique structures as well as optimized properties to adapt their living environment and fulfill functionalities.

Contents
List of Tables IV
Figure Caption VI
Chapter 1 Introduction 1
1.1 Background 1
1.2 Motivations and Goals 3
Chapter 2 Literature Review 5
2.1 Biological Material 5
2.1.1 Overview 5
2.1.2 Basic Building Blocks of Biological Materials 9
2.2 Teeth 14
2.2.1 Overview 14
2.2.2 Dentition 14
2.2.3 Micro-structure of Teeth 16
2.2.4 Teeth Shape and Feeding Mechanism 18
2.3 Functionalized Teeth 18
2.3.1 Self-sharpening Teeth 19
2.3.2 Tusk 20
2.3.3 Radula 23
2.3.4 Placoid Scales 24
2.4 Feeding Mechanisms 25
Chapter 3 Experimental Procedure 44
3.1 Sample Source 44
3.2 Structural Characterization 44
3.2.1 Macro-structural Observation 44
3.2.2 Optical Microscopy 45
3.2.3 Scanning Electronic Microscopy 45
3.3 Compositional Analysis 46
3.3.1 Energy-Dispersive Spectroscopy (EDS) 46
3.3.2 Electron Probe Microanalysis (EPMA) 47
3.3.3 Raman Spectroscopy 47
3.3.4 Fourier Transform Infrared Spectroscopy (FTIR) 47
3.4 Mechanical Property Evaluation 48
3.4.1 Nano-indentation 48
3.4.2 Wear Resistance Test 49
Chapter 4 Results and Discussion 56
4.1 Overview: Fish Teeth 56
4.2 Macroscopic Observation 56
4.3 Elemental and Compositional Analyses 59
4.3.1 Elemental Identification 59
4.3.2 Raman / FT-IR Spectrum 60
4.4 Microstructural Characterization 62
4.4.1 Optical Microscopy (OM) 62
4.4.2 Scanning Electron Microscopy (SEM) 63
4.5 Mechanical Properties 68
4.5.1 Nano-indentation Measurement 68
4.5.2 Wear Resistance Test 73
Chapter 5 Conclusions 114
Chapter 6 Future Work 118
6.1 Abrasion Test 118
6.2 Nano-fretting Test 118
6.3 Crystal Orientation Mapping (EBSD) 119
References 127

References
[1] T.-X. Fan, S.-K. Chow, and D. Zhang, "Biomorphic mineralization: From biology to materials," Progress in Materials Science, vol. 54, pp. 542-659, 2009.
[2] L. K. Grunenfelder, N. Suksangpanya, C. Salinas, G. Milliron, N. Yaraghi, S. Herrera, et al., "Bio-inspired impact-resistant composites," Acta Biomaterialia, vol. 10, pp. 3997-4008, 2014.
[3] M. A. Meyers, P.-Y. Chen, A. Y.-M. Lin, and Y. Seki, "Biological materials: Structure and mechanical properties," Progress in Materials Science, vol. 53, pp. 1-206, 2008.
[4] D. Zhang, W. Zhang, J. Gu, T. Fan, Q. Liu, H. Su, et al., "Inspiration from butterfly and moth wing scales: Characterization, modeling, and fabrication," Progress in Materials Science, vol. 68, pp. 67-96, 2015.
[5] E. Arzt, "Biological and artificial attachment devices: Lessons for materials scientists from flies and geckos," Materials Science and Engineering: C, vol. 26, pp. 1245-1250, 2006.
[6] S. Nishimoto and B. Bhushan, "Bioinspired self-cleaning surfaces with superhydrophobicity, superoleophobicity, and superhydrophilicity," RSC Advances, vol. 3, p. 671, 2013.
[7] T.-Y. N. Quan-Li Li, Ying Cao, Wei-bo Zhang, May Lei Mei and Chun Hung Chu, "A novel self-assembled oligopeptide amphiphile for biomimetic mineralization of enamel," BMC Biotechnology, vol. 14, 2014.
[8] J. Fan and J.-H. He, "Biomimic design of multi-scale fabric with efficient heat transfer property," Thermal Science, vol. 16, pp. 1349-1352, 2012.
[9] Y. Zhang, H. Yao, C. Ortiz, J. Xu, and M. Dao, "Bio-inspired interfacial strengthening strategy through geometrically interlocking designs," J Mech Behav Biomed Mater, vol. 15, pp. 70-7, Nov 2012.
[10] J. B. Ramsay and C. D. Wilga, "Morphology and mechanics of the teeth and jaws of white-spotted bamboo sharks (Chiloscyllium plagiosum)," J Morphol, vol. 268, pp. 664-82, Aug 2007.
[11] G. Pregill, "Durophagous Feeding Adaptations in an Amphisbaenid," Journal of Herpetology, vol. 18, pp. 186-191, 1984.
[12] W. X. Tseng ZJ, "Cranial functional morphology of fossil dogs and adaptation for durophagy in Borophagus and Epicyon (Carnivora, Mammalia)," Journal of Morphology, vol. 271, pp. 1386-1398, 2010.
[13] Q. W. James C. Weavera, Ali Miserezb, Anthony Tantuccioc, Ryan Strombergd, Krassimir N. Bozhilove, Peter Maxwellg, Richard Nayd, Shinobu T. Heierf, Elaine DiMasih, David Kisailusa, "Analysis of an ultra hard magnetic biomineral in chiton radular teeth," Materialstoday, vol. 13, pp. 42-52, 2010.
[14] V. H. V. Schaerlaeken, R. Boistel, P. Aerts, P. Velensky, I. Rehak, D. V. Andrade, A. Herrel, "Built to bite: Feeding kinematiccs, bite forces, and head shape of a specialized durophagous lizard, Dracaena guianensis (teiidae)." J Exp Zool A Ecol Genet Physiol, vol. 317, pp. 371-381, 2012.
[15] P.-Y. Chen, J. McKittrick, and M. A. Meyers, "Biological materials: Functional adaptations and bioinspired designs," Progress in Materials Science, vol. 57, pp. 1492-1704, 2012.
[16] G. Guidoni, J. Denkmayr, T. Schöberl, and I. Jäger, "Nanoindentation in teeth: influence of experimental conditions on local mechanical properties," Philosophical Magazine, vol. 86, pp. 5705-5714, 2006.
[17] L. Bertinetti, U. D. Hangen, M. Eder, P. Leibner, P. Fratzl, and I. Zlotnikov, "Characterizing moisture-dependent mechanical properties of organic materials: humidity-controlled static and dynamic nanoindentation of wood cell walls," Philosophical Magazine, pp. 1-7, 2014.
[18] U. G. K. Wegst and M. F. Ashby, "The mechanical efficiency of natural materials," Philosophical Magazine, vol. 84, pp. 2167-2186, 2004.
[19] H. D. Espinosa, J. E. Rim, F. Barthelat, and M. J. Buehler, "Merger of structure and material in nacre and bone – Perspectives on de novo biomimetic materials," Progress in Materials Science, vol. 54, pp. 1059-1100, 2009.
[20] J. Enax, A. M. Janus, D. Raabe, M. Epple, and H. O. Fabritius, "Ultrastructural organization and micromechanical properties of shark tooth enameloid," Acta Biomater, vol. 10, pp. 3959-68, Sep 2014.
[21] J. McKittrick, P. Y. Chen, L. Tombolato, E. E. Novitskaya, M. W. Trim, G. A. Hirata, et al., "Energy absorbent natural materials and bioinspired design strategies: A review," Materials Science and Engineering: C, vol. 30, pp. 331-342, 2010.
[22] J. D. C. P. Zioupos, "Pre-failure toughening mechanisms in the dentine of the narwhal tusk: Microscopic examination of stress/strain induced microcracking," Journal of Materials Science Letters, vol. 15, pp. 991-994, Jun 1 1996.
[23] K. E. v. H. C. K. Mathews, K. G. Ahern, Biochemistry, Third ed. San Francisco, CA: Benjamin/Cummings, Addison Wesley Longman, 2000.
[24] M. K. F. Peter, Z. Ivo, "Fibrillar structure and mechanical properties of collagen," Journal of Structural BiologyJ, vol. 122, pp. 119-122, 1997.
[25] M. Iijima, D. Fan, K. M. Bromley, Z. Sun, and J. Moradian-Oldak, "Tooth enamel proteins enamelin and amelogenin cooperate to regulate the growth morphology of octacalcium phosphate crystals," Cryst Growth Des, vol. 10, pp. 4815-4822, Nov 2010.
[26] D. J. Adams, "Fungal cell wall chitinases and glucanases," Microbiology, vol. 150, pp. 2029-35, Jul 2004.
[27] S. Vogel, Comparative biomechanics: life's physical world. Princeton, NJ: Princeton University Press, 2003.
[28] M. N. S. Hunt, "A comparative study of protein composition in the chitin-protein complexes of the beak, pen, sucker disc, radula and oesophageal cuticle of cephalopods," Comp. Biochem. Physiol., vol. 68B, pp. 535-546, 1981.
[29] F. J. Alvarez, "The effect of chitin size, shape, source and purification method on immune recognition," Molecules, vol. 19, pp. 4433-51, 2014.
[30] M. N. V. R. Kumar, "A review of chitin and chitosan applications," Reactive & Functional Polymers, vol. 46, pp. 1-27, 2000.
[31] M. Rinaudo, "Chitin and chitosan: Properties and applications," Progress in Polymer Science, vol. 31, pp. 603-632, 2006.
[32] R. A. Y. M. I. Kay, A. S. Posner, "Crystal Structure of Hydroxyapatite," Nature, vol. 204, 1964.
[33] K. H. T. Sakae, H. Yamamoto, K. Suzuki, Y. Hayakawa, Y. Takahashi, T. Kuwada, K. Nakao, K. Nogami, M. Inagaki, T. Tanaka, K. Hayakawa, I. Sato, M. Kakei, "Three-dimensional orientation analysis of human enamel crystallites using x-ray diffraction," Journal of Hard Tissue Biology, vol. 20, pp. 7-11, 2011.
[34] M. Duer and A. Veis, "Bone mineralization: Water brings order," Nat Mater, vol. 12, pp. 1081-1082, 12//print 2013.
[35] L. H. M. Despina S. Koussoulakou, Stauros L. Koussoulakos, "A Curriculum Vitae of Teeth_Evolution, Generation, Regeneration," International Journals of Biological Sciences, vol. 5, pp. 226-243
[36] T. Davit-Beal, F. Allizard, and J. Y. Sire, "Enameloid/enamel transition through successive tooth replacements in Pleurodeles waltl (Lissamphibia, Caudata)," Cell Tissue Res, vol. 328, pp. 167-83, Apr 2007.
[37] J. D. Currey, "The design of mineralised hard tissues for their mechanical functions," The Journal of Experimental Biology vol. 202, pp. 3285-3294, 1999.
[38] "K.-J. Söderholm (2012). Fracture of Dental Materials, Applied Fracture Mechanics, Dr. Alexander Belov (Ed.), ISBN: 978-953-51-0897-9, InTech, DOI: 10.5772/48354. Available from: http://www.intechopen.com/books/applied-fracture-mechanics/fracture-of-dental-materials," ed.
[39] C. D. Lynch, V. R. O'Sullivan, P. Dockery, C. T. McGillycuddy, and A. J. Sloan, "Hunter-Schreger Band patterns in human tooth enamel," J Anat, vol. 217, pp. 106-15, Aug 2010.
[40] C. D. W. A. P. J. Motta, "Durophagy in sharks: feeding mechanics of the hammerhead sphyrna tiburo " The Journal of Experimental Biology, vol. 203, pp. 2781-2796, 2000.
[41] A. M. Reiter, "Pathophysiology of Dental Disease in the Rabbit, Guinea Pig, and Chinchilla," Journal of Exotic Pet Medicine, vol. 17, pp. 70-77, 2008.
[42] P. Y. Chen, A. Y. Lin, Y. S. Lin, Y. Seki, A. G. Stokes, J. Peyras, et al., "Structure and mechanical properties of selected biological materials," J Mech Behav Biomed Mater, vol. 1, pp. 208-26, Jul 2008.
[43] C. E. Killian, R. A. Metzler, Y. Gong, T. H. Churchill, I. C. Olson, V. Trubetskoy, et al., "Self-Sharpening Mechanism of the Sea Urchin Tooth," Advanced Functional Materials, vol. 21, pp. 682-690, 2011.
[44] M. T. Nweeia, F. C. Eichmiller, P. V. Hauschka, E. Tyler, J. G. Mead, C. W. Potter, et al., "Vestigial tooth anatomy and tusk nomenclature for monodon monoceros," Anat Rec (Hoboken), vol. 295, pp. 1006-16, Jun 2012.
[45] J. D. Currey, "Mechanical properties and adaptations of some less familiar bony tissues," J Mech Behav Biomed Mater, vol. 3, pp. 357-72, Jul 2010.
[46] M. T. Nweeia, F. C. Eichmiller, P. V. Hauschka, G. A. Donahue, J. R. Orr, S. H. Ferguson, et al., "Sensory ability in the narwhal tooth organ system," Anat Rec (Hoboken), vol. 297, pp. 599-617, Apr 2014.
[47] M. B. Jakubinek, C. J. Samarasekera, and M. A. White, "Elephant ivory: A low thermal conductivity, high strength nanocomposite," Journal of Materials Research, vol. 21, pp. 287-292, 2011.
[48] M. Locke, "Structure of ivory," J Morphol, vol. 269, pp. 423-50, Apr 2008.
[49] H. B. W. F.Z. Cui, H.B. Zhang, H.D. Li and D.C. Liu "Anisotropic indentation morphology and hardness of natural ivory " Materials Science and Engineering C, vol. 2, pp. 87-91 1994.
[50] R. Nalla, "Effect of orientation on the in vitro fracture toughness of dentin: the role of toughening mechanisms," Biomaterials, vol. 24, pp. 3955-3968, 2003.
[51] S. H. K. E.-Y. Chung, Y. H. Back, "Observations of boring behaviour and the drilling mechanism of Lunatia fortunei (Gastropoda: Naticidae) in western Korea," Korean J. Malacol. , vol. 27, pp. 253-259, 2011.
[52] L. M. Gordon and D. Joester, "Nanoscale chemical tomography of buried organic-inorganic interfaces in the chiton tooth," Nature, vol. 469, pp. 194-7, Jan 13 2011.
[53] C.-W. L. T.-E. Hua, "Silica biomineralization in the radula of a limpet Notoacmea schrenckii (Gastrpoda Acmaeidae)," Zoological Studies, vol. 46, pp. 379-388 2007.
[54] D. Lu and A. H. Barber, "Optimized nanoscale composite behaviour in limpet teeth," J R Soc Interface, vol. 9, pp. 1318-24, Jun 7 2012.
[55] J. B. d. P. N. V. Haddad 2nd, and V. J.Cobo, "Venomous mollusks: the risks of human accidents by Conus snails (Gastropoda: Conidae) in Brazil," Rev. Soc. Bras. Med. Trop., vol. 39, pp. 498-500, 2006.
[56] B. Dean and B. Bhushan, "Shark-skin surfaces for fluid-drag reduction in turbulent flow: a review," Philos Trans A Math Phys Eng Sci, vol. 368, pp. 4775-806, Oct 28 2010.
[57] Y. C. Jung and B. Bhushan, "Biomimetic structures for fluid drag reduction in laminar and turbulent flows," J Phys Condens Matter, vol. 22, p. 035104, Jan 27 2010.
[58] C. D. Wilga, P. J. Motta, and C. P. Sanford, "Evolution and ecology of feeding in elasmobranchs," Integr Comp Biol, vol. 47, pp. 55-69, Jul 2007.
[59] B. Jordan, "The morphology and biomechanics of jaw strcutures in chondrichthyes," Open Access Master's Theses, Department of Biological and Environement Sciences, University of Rhode Island, 2013.
[60] G. KM, Encyclopedia of Fish Physiology: From Genome to Environment. San Diego: Academic Press, 2011.
[61] P. Wainwright, A. M. Carroll, D. C. Collar, S. W. Day, T. E. Higham, and R. A. Holzman, "Suction feeding mechanics, performance, and diversity in fishes," Integr Comp Biol, vol. 47, pp. 96-106, Jul 2007.
[62] T. C. T. P. J. Motta, R. E. Summers, A. P. Summers, "Feeding mechanism and functional morphology of the jaws of the lemon shark Negaprion brevirostris (Chondrichthyes, Carcharhinidae)," The Journal of Experimental Biology, vol. 200, pp. 2765-2780, 1997.
[63] P. J. Motta, M. Maslanka, R. E. Hueter, R. L. Davis, R. de la Parra, S. L. Mulvany, et al., "Feeding anatomy, filter-feeding rate, and diet of whale sharks Rhincodon typus during surface ram filter feeding off the Yucatan Peninsula, Mexico," Zoology (Jena), vol. 113, pp. 199-212, Aug 2010.
[64] A. K. A. CARR, I. TIBBETTS, R. TRUSS & J. DRENNAN, "Microstructure of pharyngeal tooth enameloid in the parrotfish Scarus rivulatus," Journal of Microscopy, vol. 221, pp. 8-16, 2006.
[65] I. Solomonov, D. Talmi-Frank, Y. Milstein, S. Addadi, A. Aloshin, and I. Sagi, "Introduction of correlative light and airSEMTM microscopy imaging for tissue research under ambient conditions," Sci. Rep., vol. 4, 08/07/online 2014.
[66] http://en.wikipedia.org/wiki/Radula.
[67] D. G. R. a. Y.-M. Mak, "Indirect evidence for ecophenotypic plasticity in radular dentition of Littoraria species (Gastropoda Littorinidae)," J. Moll. Stud., vol. 65, pp. 355-370, 1999.
[68] J. Kaczmarek, Principles of machining by cutting, abrasion and erosion / by J. Kaczmarek ; translated by A. Voellnagel, (parts 1-3) and E. Lepa, (part 4). Stevenage [Eng.]: P. Peregrinus, 1976.
[69] K. G. Budinski, Surface engineering for wear resistance. Englewood Cliffs, N.J: Prentice Hall, 1988.
[70] R. Z. L. a. S. i. Suga, "Crystallographic nature of fluoride in enameloids of fish," Calcif. Tissue Int. , vol. 32, pp. 169-174 1980.
[71] I. Sasagawa, "Mineralization patterns in elasmobranch fish," Microsc Res Tech, vol. 59, pp. 396-407, Dec 1 2002.
[72] G. Guinot and H. Cappetta, "Enameloid microstructure of some Cretaceous Hexanchiformes and Synechodontiformes (Chondrichthyes, Neoselachii): new structures and systematic implications," Microsc Res Tech, vol. 74, pp. 196-205, Feb 2011.
[73] G. Penel, G. Leroy, C. Rey, B. Sombret, J. P. Huvenne, and E. Bres, "Infrared and Raman microspectrometry study of fluor-fluor-hydroxy and hydroxy-apatite powders," Journal of Materials Science-Materials in Medicine, vol. 8, pp. 271-276, May 1997.
[74] A. Awonusi, M. D. Morris, and M. M. Tecklenburg, "Carbonate assignment and calibration in the Raman spectrum of apatite," Calcif Tissue Int, vol. 81, pp. 46-52, Jul 2007.
[75] C. E. Hughes and C. A. White, "Crack propagation in teeth: a comparison of perimortem and postmortem behavior of dental materials and cracks," J Forensic Sci, vol. 54, pp. 263-6, Mar 2009.
[76] M. Giannini, "Ultimate tensile strength of tooth structures," Dental Materials, vol. 20, pp. 322-329, 2004.
[77] L. B. Whitenack, D. C. Simkins, Jr., and P. J. Motta, "Biology meets engineering: the structural mechanics of fossil and extant shark teeth," J Morphol, vol. 272, pp. 169-79, Feb 2011.
[78] W. C. O. a. G. M. Pharr, "An improved technique for determining hardness and elastic modulus using load and displacement sensing indentation experiments," J. Master. Res., vol. 7, pp. 1564-1583, 1992.
[79] H. Li, "Structural Origin of Mechanical Prowess In Conch Shells," Doctor dissertation, Philosophy in Mechanical Engineering, University of South Carolina, 2009

[80] K. R. Mara, P. J. Motta, and D. R. Huber, "Bite force and performance in the durophagous bonnethead shark, Sphyrna tiburo," J Exp Zool A Ecol Genet Physiol, vol. 313, pp. 95-105, Feb 1 2010.
[81] P.-Y. Chen, J. Schirer, A. Simpson, R. Nay, Y.-S. Lin, W. Yang, et al., "Predation versus protection: Fish teeth and scales evaluated by nanoindentation," Journal of Materials Research, vol. 27, pp. 100-112, 2011.
[82] S. D. a. S. Risnes, "A comparative infrared spectroscopic study of hydroxide and carbonate absorption bands in spectra of shark enameloid, shark dentin, and a geological apatite," Calcif Tissue Int, vol. 65, pp. 459-465, 1999.
[83] R. Hmaidouch and P. Weigl, "Tooth wear against ceramic crowns in posterior region: a systematic literature review," Int J Oral Sci, vol. 5, pp. 183-90, Dec 2013.
[84] P. Suwannaroop, P. Chaijareenont, N. Koottathape, H. Takahashi, and M. Arksornnukit, "In vitro wear resistance, hardness and elastic modulus of artificial denture teet," Dental Materials Journal, vol. 30, pp. 461-468, 2011.
[85] M. H. Zhu, H. Y. Yu, and Z. R. Zhou, "Radial fretting behaviours of dental ceramics," Tribology International, vol. 39, pp. 1255-1261, 2006.
[86] A. J. Goetz, E. Griesshaber, R. Abel, T. Fehr, B. Ruthensteiner, and W. W. Schmahl, "Tailored order: the mesocrystalline nature of sea urchin teeth," Acta Biomater, vol. 10, pp. 3885-98, Sep 2014.
[87] Y. Y. Kim, A. S. Schenk, J. Ihli, A. N. Kulak, N. B. Hetherington, C. C. Tang, et al., "A critical analysis of calcium carbonate mesocrystals," Nat Commun, vol. 5, p. 4341, 2014.