鈦金屬及其合金具有良好的機械性質及生物相容性，但由於其為生物惰性材料導致骨誘導能力較差，造成無法與骨組織達到良好的骨整合。微弧氧化（Micro-arc oxidation, MAO）製程容易且具成本效益，可在金屬表面形成微米級多孔結構之塗層，因此被廣泛用於鈦金屬表面處理。田口方法（Taguchi method）透過建立直交表（Orthogonal Array, OA）執行實驗並藉由信號雜訊比（Signal to Noise Ratio, S/N）得出最佳參數組合。
本研究將以MAO作為純鈦金屬的表面處理技術，其中電解質成分含有鈣與磷元素，能製備出具有生物活性之微米級多孔陶瓷塗層結構，並以田口方法評估MAO製程參數(正電壓、負電壓、反應時間、溶液濃度及佔空比)對於塗層之化學組成、微結構及生物活性反應的影響，進而挑選出具有最佳生物親和性之微弧氧化參數。
田口實驗結果顯示，正電壓與溶液濃度對陶瓷塗層具有最顯著影響，其中隨著正電壓與溶液濃度的增加，鈣磷含量、金紅石相、相轉換率、孔洞尺寸、粗糙度與塗層厚度皆有正相關的表現，因電壓與溶液濃度的增加會使電場增強進而產生高溫環境與強大火花，提供鈣磷離子更高的驅動力，使其擴散與電遷移進入到陶瓷塗層中，而高溫環境也促使相變化更容易發生。微弧氧化過程中，大火花的產生不但使孔洞尺寸增加，同時有助於塗層的沉積，使得表面粗糙度與塗層厚度也隨之增加。在體外生物活性試驗中，誘導磷灰石析出的能力以及細胞生長率也隨著電壓增加而增加。原因是，當電壓增強時，不僅使塗層內的鈣與磷離子含量增加，也擴大孔洞尺寸以及使表面更為粗糙，營造出適合細胞生長的環境。

Titanium and its alloys have good mechanical properties and biocompatibility. However, titanium is bioinert, which cannot firm combination with bone tissues. Micro-arc oxidation (MAO) can form microporous structure coatings on the surface of titanium. Taguchi method can predict the optimum condition by orthogonal arrays and signal-to-noise ratio (S/N), which is an approach for designing experiments.
In this study, microporous structure ceramic coating with bioactivity was formed on titanium surface using Ca/P-based electrolyte MAO process. Taguchi method was used to evaluate the effects on parameters of MAO process (positive and negative voltage, reaction time, solution concentration and duty cycle) and properties of coating, including chemical composition, microstructure and bioactivity. Therefore, the optimum combination of parameters for biocompatibility can be predicted.
The Taguchi experimental results show that the positive voltage and solution concentration significantly affects the ceramic coating. With the increase of positive voltage and solution concentration, the chemical composition (Ca and P ions) and microstructure (amount of rutile, pore size, roughness and thickness of coating) show positive correlation. Since the increased positive voltage and solution concentration provide enhanced electric field, which create high temperature environment and stronger sparks. It contributes higher driving force for Ca and P ions into the ceramic coating through diffusion and electro-migration, high temperature induced large energy gives sufficient activation energy for anatase to rutile phase transformation. The strong sparks result in larger pore size, thicker deposition of the coating and increased roughness. At in vitro test, the induced ability of apatite precipitation and cell proliferation is enhanced with increased positive voltage.

[1] S.V. Dorozhkin, Bioceramics of calcium orthophosphates, Biomaterials 31(7) (2010) 1465-1485.
[2] P. Feng, J. He, S. Peng, C. Gao, Z. Zhao, S. Xiong, C. Shuai, Characterizations and interfacial reinforcement mechanisms of multicomponent biopolymer based scaffold, Materials science & engineering. C, Materials for biological applications 100 (2019) 809-825.
[3] J. Park, R.S. Lakes, Biomaterials: an introduction, Springer Science & Business Media2007.
[4] M. McCracken, Dental implant materials: commercially pure titanium and titanium alloys, Journal of prosthodontics 8(1) (1999) 40-43.
[5] M. Balazic, J. Kopac, M.J. Jackson, W. Ahmed, Titanium and titanium alloy applications in medicine, International Journal of Nano and Biomaterials 1(1) (2007) 3-34.
[6] B. Bannon, E. Mild, Titanium alloys for biomaterial application: an overview, Titanium alloys in surgical implants, ASTM International1983.
[7] M. Niinomi, C.J. Boehlert, Titanium alloys for biomedical applications, Advances in Metallic Biomaterials, Springer2015, pp. 179-213.
[8] H. Sibum, Titanium and Titanium Alloys—From Raw Material to Semi‐finished Products, Advanced Engineering Materials 5(6) (2003) 393-398.
[9] M. Niinomi, Recent metallic materials for biomedical applications, Metallurgical and materials transactions A 33(3) (2002) 477.
[10] V. Oliveira, R. Chaves, R. Bertazzoli, R. Caram, Preparation and characterization of Ti-Al-Nb alloys for orthopedic implants, Brazilian Journal of Chemical Engineering 15(4) (1998) 326-333.
[11] A. Krząkała, K. Służalska, G. Dercz, A. Maciej, A. Kazek, J. Szade, A. Winiarski, M. Dudek, J. Michalska, G. Tylko, Characterisation of bioactive films on Ti–6Al–4V alloy, Electrochimica Acta 104 (2013) 425-438.
[12] K. Wang, The use of titanium for medical applications in the USA, Materials Science and Engineering: A 213(1-2) (1996) 134-137.
[13] W.L. Murphy, T.C. McDevitt, A.J. Engler, Materials as stem cell regulators, Nature materials 13(6) (2014) 547-557.
[14] R. Zhou, D. Wei, J. Cao, W. Feng, S. Cheng, Q. Du, B. Li, Y. Wang, D. Jia, Y. Zhou, Synergistic effects of surface chemistry and topologic structure from modified microarc oxidation coatings on Ti implants for improving osseointegration, ACS applied materials & interfaces 7(16) (2015) 8932-8941.
[15] L. Zhao, S. Mei, P.K. Chu, Y. Zhang, Z. Wu, The influence of hierarchical hybrid micro/nano-textured titanium surface with titania nanotubes on osteoblast functions, Biomaterials 31(19) (2010) 5072-5082.
[16] H. Ishizawa, M. Ogino, Thin hydroxyapatite layers formed on porous titanium using electrochemical and hydrothermal reaction, Journal of materials science 31(23) (1996) 6279-6284.
[17] T. Albrektsson, P.-I. Brånemark, H.-A. Hansson, J. Lindström, Osseointegrated titanium implants: requirements for ensuring a long-lasting, direct bone-to-implant anchorage in man, Acta Orthopaedica Scandinavica 52(2) (1981) 155-170.
[18] Y. Liu, D. Luo, T. Wang, Hierarchical structures of bone and bioinspired bone tissue engineering, Small 12(34) (2016) 4611-4632.
[19] M.M. Stevens, J.H. George, Exploring and engineering the cell surface interface, Science 310(5751) (2005) 1135-1138.
[20] W.-H. Song, Y.-K. Jun, Y. Han, S.-H. Hong, Biomimetic apatite coatings on micro-arc oxidized titania, Biomaterials 25(17) (2004) 3341-3349.
[21] S. Abbasi, F. Golestani-Fard, H. Rezaie, S. Mirhosseini, A. Ziaee, MAO-derived hydroxyapatite–TiO2 nanostructured bio-ceramic films on titanium, Materials Research Bulletin 47(11) (2012) 3407-3412.
[22] D. Ke, A.A. Vu, A. Bandyopadhyay, S. Bose, Compositionally graded doped hydroxyapatite coating on titanium using laser and plasma spray deposition for bone implants, Acta biomaterialia 84 (2019) 414-423.
[23] E. Ahounbar, S.M.M. Khoei, H. Omidvar, Characteristics of in-situ synthesized hydroxyapatite on TiO2 ceramic via plasma electrolytic oxidation, Ceramics International 45(3) (2019) 3118-3125.
[24] Y. Zhu, K. Zhang, R. Zhao, X. Ye, X. Chen, Z. Xiao, X. Yang, X. Zhu, K. Zhang, Y. Fan, Bone regeneration with micro/nano hybrid-structured biphasic calcium phosphate bioceramics at segmental bone defect and the induced immunoregulation of MSCs, Biomaterials 147 (2017) 133-144.
[25] A. Najafinezhad, M. Abdellahi, H. Ghayour, A. Soheily, A. Chami, A. Khandan, A comparative study on the synthesis mechanism, bioactivity and mechanical properties of three silicate bioceramics, Materials Science and Engineering: C 72 (2017) 259-267.
[26] Y. Wang, H. Yu, C. Chen, Z. Zhao, Review of the biocompatibility of micro-arc oxidation coated titanium alloys, Materials & Design 85 (2015) 640-652.
[27] A. Yerokhin, X. Nie, A. Leyland, A. Matthews, S. Dowey, Plasma electrolysis for surface engineering, Surface and coatings technology 122(2-3) (1999) 73-93.
[28] R.A. Fisher, The design of experiments, The design of experiments. (7th Ed) (1960).
[29] R.A. Fisher, Design of experiments, Br Med J 1(3923) (1936) 554-554.
[30] D.C. Montgomery, Design and analysis of experiments, John wiley & sons2017.
[31] M.J. Anderson, P.J. Whitcomb, Design of experiments, Kirk‐Othmer Encyclopedia of Chemical Technology (2000) 1-22.
[32] K. Dehnad, Quality Control, Robust Design, and the Taguchi Method, Springer US2012.
[33] Y. Vangolu, E. Arslan, Y. Totik, E. Demirci, A. Alsaran, Optimization of the coating parameters for micro-arc oxidation of Cp-Ti, Surface and Coatings Technology 205(6) (2010) 1764-1773.
[34] S. Luo, Q. Wang, R. Ye, C.S. Ramachandran, Effects of electrolyte concentration on the microstructure and properties of plasma electrolytic oxidation coatings on Ti-6Al-4V alloy, Surface and Coatings Technology 375 (2019) 864-876.
[35] S.-Y. Jian, M.-L. Ho, B.-C. Shih, Y.-J. Wang, L.-W. Weng, M.-W. Wang, C.-C. Tseng, Evaluation of the corrosion resistance and cytocompatibility of a bioactive micro-arc oxidation Coating on AZ31 Mg alloy, Coatings 9(6) (2019) 396.
[36] Y. Ma, H. Hu, D. Northwood, X. Nie, Optimization of the electrolytic plasma oxidation processes for corrosion protection of magnesium alloy AM50 using the Taguchi method, Journal of materials processing technology 182(1-3) (2007) 58-64.
[37] Y. Ma, X. Nie, D. Northwood, H. Hu, Systematic study of the electrolytic plasma oxidation process on a Mg alloy for corrosion protection, Thin Solid Films 494(1-2) (2006) 296-301.
[38] R. Zhang, D. Shan, R. Chen, E. Han, Effects of electric parameters on properties of anodic coatings formed on magnesium alloys, Materials Chemistry and Physics 107(2-3) (2008) 356-363.
[39] H.F. Nabavi, M. Aliofkhazraei, A.S. Rouhaghdam, Electrical characteristics and discharge properties of hybrid plasma electrolytic oxidation on titanium, Journal of alloys and compounds 728 (2017) 464-475.
[40] L. Qiao, J. Lou, S. Zhang, B. Qu, W. Chang, R. Zhang, The entrance mechanism of calcium and phosphorus elements into micro arc oxidation coatings developed on Ti6Al4V alloy, Surface and Coatings Technology 285 (2016) 187-196.
[41] I. Han, J.H. Choi, B.H. Zhao, H.K. Baik, I.-S. Lee, Micro-arc oxidation in various concentration of KOH and structural change by different cut off potential, Current Applied Physics 7 (2007) e23-e27.
[42] T. Wanxia, Y. Jikang, Y. Gang, G. Guoyou, D. Jinghong, Z. Jiamin, L. Yichun, S. Zhe, Y. Jianhong, Effect of electrolytic solution concentrations on surface hydrophilicity of micro-arc oxidation ceramic film based on Ti6Al4V titanium alloy, Rare Metal Materials and Engineering 43(12) (2014) 2883-2888.
[43] K. Venkateswarlu, S. Suresh, N. Rameshbabu, A.C. Bose, S. Subramanian, Effect of electrolyte chemistry on the structural, morphological and corrosion characteristics of titania films developed on Ti-6Al-4V implant material by plasma electrolytic oxidation, Key Engineering Materials, Trans Tech Publ, 2012, pp. 436-441.
[44] R. Van Noort, Titanium: the implant material of today, Journal of Materials Science 22(11) (1987) 3801-3811.
[45] J. Lausmaa, L. Mattsson, U. Rolander, B. Kasemo, Chemical composition and morphology of titanium surface oxides, MRS Online Proceedings Library Archive 55 (1985).
[46] J. Ong, L. Lucas, R. Connatser, J. Gregory, Spectroscopic characterization of passivated titanium in a physiologic solution, Journal of Materials Science: Materials in Medicine 6(2) (1995) 113-119.
[47] R.H. Khan, A. Yerokhin, A. Matthews, Structural characteristics and residual stresses in oxide films produced on Ti by pulsed unipolar plasma electrolytic oxidation, Philosophical Magazine 88(6) (2008) 795-807.
[48] A.A. Gribb, J.F. Banfield, Particle size effects on transformation kinetics and phase stability in nanocrystalline TiO2, American Mineralogist 82(7-8) (1997) 717-728.
[49] O. Camara, C. De Pauli, M. Giordano, Potentiodynamic behaviour of mechanically polished titanium electrodes, Electrochimica acta 29(8) (1984) 1111-1117.
[50] A. Felske, W. Plieth, Raman spectroscopy of titanium dioxide layers, Electrochimica Acta 34(1) (1989) 75-77.
[51] L.-H. Li, Y.-M. Kong, H.-W. Kim, Y.-W. Kim, H.-E. Kim, S.-J. Heo, J.-Y. Koak, Improved biological performance of Ti implants due to surface modification by micro-arc oxidation, Biomaterials 25(14) (2004) 2867-2875.
[52] H. Hu, W. Zhang, Y. Qiao, X. Jiang, X. Liu, C. Ding, Antibacterial activity and increased bone marrow stem cell functions of Zn-incorporated TiO2 coatings on titanium, Acta biomaterialia 8(2) (2012) 904-915.
[53] S. Sangeetha, S.R. Kathyayini, P.D. Raj, P. Dhivya, M. Sridharan, Biocompatibility studies on TiO 2 coated Ti surface, International Conference on Advanced Nanomaterials & Emerging Engineering Technologies, IEEE, 2013, pp. 404-408.
[54] M. Uchida, H.M. Kim, T. Kokubo, S. Fujibayashi, T. Nakamura, Structural dependence of apatite formation on titania gels in a simulated body fluid, Journal of Biomedical Materials Research Part A: An Official Journal of The Society for Biomaterials, The Japanese Society for Biomaterials, and The Australian Society for Biomaterials and the Korean Society for Biomaterials 64(1) (2003) 164-170.
[55] M. Carballo‐Vila, B. Moreno‐Burriel, E. Chinarro, J.R. Jurado, N. Casañ‐Pastor, J.E. Collazos‐Castro, Titanium oxide as substrate for neural cell growth, Journal of Biomedical Materials Research Part A: An Official Journal of The Society for Biomaterials, The Japanese Society for Biomaterials, and The Australian Society for Biomaterials and the Korean Society for Biomaterials 90(1) (2009) 94-105.
[56] K. Nakazawa, S. Lee, J. Fukuda, D. Yang, T. Kunitake, Hepatocyte spheroid formation on a titanium dioxide gel surface and hepatocyte long-term culture, Journal of Materials Science: Materials in Medicine 17(4) (2006) 359-364.
[57] S. Buchloh, B. Stieger, P. Meier, L. Gauckler, Hepatocyte performance on different crystallographic faces of rutile, Biomaterials 24(15) (2003) 2605-2610.
[58] L. Zhao, J. Chang, W. Zhai, Effect of crystallographic phases of TiO2 on hepatocyte attachment, proliferation and morphology, Journal of biomaterials applications 19(3) (2005) 237-252.
[59] H.K. Tsou, P.Y. Hsieh, M.H. Chi, C.J. Chung, J.L. He, Improved osteoblast compatibility of medical‐grade polyetheretherketone using arc ionplated rutile/anatase titanium dioxide films for spinal implants, Journal of Biomedical Materials Research Part A 100(10) (2012) 2787-2792.
[60] B. Groessner-Schreiber, R.S. Tuan, Enhanced extracellular matrix production and mineralization by osteoblasts cultured on titanium surfaces in vitro, Journal of cell science 101(1) (1992) 209-217.
[61] C. Wang, F. Wang, Y. Han, Structural characteristics and outward–inward growth behavior of tantalum oxide coatings on tantalum by micro-arc oxidation, Surface and Coatings Technology 214 (2013) 110-116.
[62] B. Yang, M. Uchida, H.-M. Kim, X. Zhang, T. Kokubo, Preparation of bioactive titanium metal via anodic oxidation treatment, Biomaterials 25(6) (2004) 1003-1010.
[63] Y. Yan, J. Sun, Y. Han, D. Li, K. Cui, Microstructure and bioactivity of Ca, P and Sr doped TiO2 coating formed on porous titanium by micro-arc oxidation, Surface and Coatings Technology 205(6) (2010) 1702-1713.
[64] J. Weng, Q. Liu, J. Wolke, D. Zhang, K. De Groot, The role of amorphous phase in nucleating bone-like apatite on plasma-sprayed hydroxyapatite coatings in simulated body fluid, Journal of materials science letters 16(4) (1997) 335-337.
[65] A.H. Heuer, D. Fink, V. Laraia, J. Arias, P. Calvert, K. Kendall, G.L. Messing, J. Blackwell, P. Rieke, D. Thompson, Innovative materials processing strategies: a biomimetic approach, Science 255(5048) (1992) 1098-1105.
[66] H. Wen, Q. Liu, J. De Wijn, K. De Groot, F. Cui, Preparation of bioactive microporous titanium surface by a new two-step chemical treatment, Journal of Materials Science: Materials in Medicine 9(3) (1998) 121-128.
[67] Y. Wang, J. Guo, J. Zhuang, Y. Jing, Z. Shao, M. Jin, J. Zhang, D. Wei, Y. Zhou, Development and characterization of MAO bioactive ceramic coating grown on micro-patterned Ti6Al4V alloy surface, Applied surface science 299 (2014) 58-65.