1. Effect of Storage Temperature on Ti-6Al-4V Surface Wettability Caio Peixoto*, Arman Butt** and Christos Takoudis** *Federal University of Rio Grande do Norte **University of Illinois at Chicago

2. Outline Motivation and Background Sample Preparation Surface Characterization –Roughness (Zygo) –Chemistry (Fourier Transform Infrared Spectroscopy – FTIR) –Wettability (Water Contact Angle) Conclusions 2 2 2 2

3. Motivation and Background

4. Titanium and Alloys Corrosion resistance, mechanical properties and biocompatibility Numerous biomedical applications –Dentistry –Orthopaedics –Cardiovascular –Ophthalmology 2 2 Figure from Geetha Manivasagam et al. Biomedical Implants: Corrosion and its Prevention - A Review. Recent Patents on Corrosion Science. 2010, pp. 40-54. 3 3

5. Osseointegration Connection between the implant and the living bone Prevention of implant loosening 3 3 Figure adapted from M. Geetha et al. Ti based biomaterials, the ultimate choice for orthopaedic implants - A review. Pregress in Materials Science. 2009, pp. 397-425. 4 4 Water adsorption Proteins adsorption Cells adsorption

6. Water Dissociation on TiO 2 Surface 3 3 Figure adapted from Z. Zhang et al. Imaging Water Dissociation on TiO2(110): Evidence for Inequivalent Geminate OH Groups J. Phys. Chem. B 2006, 110, 21840-21845 5 5 (a)TiO 2 surface with oxygen vacancy (b) Two hydroxyl groups H V (at a vacancy) and H B (protonation of neighbor oxygen atom) formed by water adsorption and dissociation (c)H B diffusion

7. Motivation Current storage method: samples in air (Petri-dish or Kimwipe Decrease in wettability over time Materials can be mistakenly classified as bad by further tests 6 6 Evolution of water contact angle – Samples stored in glass petri –dish in air (Data acquisition and graph preparation by Sweetu Patel) 6 6 Samples in current storage conditions

8. Background Surface wettability decreases over time due to poor storage methods 1 At 2x10 -10 Torr, increase in temperature results in water desorption and hydroxyl group loss 2 7 7 [1] Jung Hwa Park et al. Effect of cleaning and sterilization on titanium implant surface properties and cellular response. Acta Biomaterialia, 2011 [2] Amy L. Linsebigler, et al. Photocatalysis on TiOn Surfaces: Principles, Mechanisms, and Selected Results. Chem. Rev. 1995, 95, 735-758. 7 7

9. Sample Preparation

10. Sandblasting –50 µm alumina grit particles –517 kPa 2 2 8 8 Acid Etching Figure from L.G. Harris, et al.Staphylococcus aureus adhesion to titanium oxide surfaces coated with non-functionalized and peptide-functionalized poly(l-lysine)-grafted-poly(ethylene glycol) copolymers, Biomaterials, Volume 25, Issue 18, August 2004 H 2 SO 4 + H 2 O 2 H 2 SO 5 + H 2 O

11. Sample Preparation Sonication – 1 hour methanol (99.8%) Wash – 30 seconds deionized water (DI-water) Annealing – 3h in air 2 2 9 9 AnnealingScheme (adapted from http://www.memsnet.org/mems/processes/deposition.html) Not Annealed 400 ºC 600 ºC

12. AnnealingStorage Condition Group 1 Not Annealed Kimwipe Group 2Room Temp. DI-Water Group 3Cold DI-Water* Group 4 400 ºC Kimwipe Group 5Room Temp. DI-Water Group 6Cold DI-Water* Group 7 600 ºC Kimwipe Group 8Room Temp. DI-Water Group 9Cold DI-Water* 10 *Refrigerator temperature: 8 ± 2 ºC

13. Surface Characterization

14. Zygo 4 4 11 Roughness (µm) Not Annealed400 ºC600 ºC RMS2.27 ± 0.272.57 ± 0.472.51 ± 0.56 Sample 45 surface

15. FTIR 4 4 12 Infrared Spectrum (absorbance) Deconvolution using XPSpeak Figure from http://www.bgtu.net/image/ik.jpg

16. 13

17. 14

18. 15 Anatase Ti-O bond

19. 16

20. 17 Rutile V-O Al2O3

21. 18 Al 2 O 3

22. Water Contact Angle Water contact angle measurements – After 0h, 3h, 6h,12h, 1d, 2d, 6d, 9d,13d, 16d and 20d Cold water groups let to warm up to room temperature –Measurements after 20d3h, 20d6h, 20d12h, 21d, 23d and 27d Warm up all the samples to 37 °C –Measurements after 27d3h, 27d6h, 27d12h, 28d, 30d, 34d 4 4 19

23. 20 Cold water samples warmed up to room temperature Samples immersed in water and warmed up to 37 ºC

24. 21 Cold water samples warmed up to room temperature Samples immersed in water and warmed up to 37 ºC

25. 22 Cold water samples warmed up to room temperature Samples immersed in water and warmed up to 37 ºC

26. 23 Conclusions Best annealing temperature: 600 ºC –Rutile formation –Signatures related to vanadium and aluminum oxides from FTIR spectrum Water Contact Angle After 34 Days (º) Not Annealed400 ºC600 ºC Kimwipe61 ± 1054 ± 1031 ± 13 Room Temperature Water12 ± 4 7 ± 2 Cold Water9 ± 312 ± 44 ± 2

27. 24 Conclusions Best storage condition: immersed in DI-water –Storage temperature showed no major effect –Samples wrapped in Kimwipe decreased drastically when immersed in DI-water –Water dissociation reaches equilibrium Figure adapted from Z. Zhang et al. Imaging Water Dissociation on TiO2(110): Evidence for Inequivalent Geminate OH Groups J. Phys. Chem. B 2006, 110, 21840-21845

28. Acknowledgments Dr. Gregory Jursich, Sweetu Patel, Azhang Hamlekhan and Dmitry Royhman

29. Questions? Comments?