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Investigation of DLC Film Stability on Stainless Steel via Tensile Testing for Biocompatibility

This study examines the stability of diamond-like carbon (DLC) films deposited on stainless steel for biomedical applications, particularly as stents. Through tensile testing, the adhesion between the DLC layer and substrate is analyzed under varying preprocessing conditions including argon cleaning, buffer layer thickness, and annealing temperatures. Results indicate optimal adhesion occurs with careful adjustment of processing parameters, revealing critical insights into wear resistance and potential enhancement for biological applications.

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Investigation of DLC Film Stability on Stainless Steel via Tensile Testing for Biocompatibility

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  1. DLC 20μm Si buffer layer ( 2m30s – 15min) Ar pre-cleaning (15-60min) SUS 304 SUS 304 0.09-0.12mm (a) 100μm 20μm (b) (d) (c) (b) (c) (a) 20μm 20μm 20μm 20μm 20μm 20μm (d) Heart Valve Stability of DLC film on stainless steel investigated by tensile-test H. W. Choi1,2, K. -R. Lee, R. Wang3, K. H. Oh2 • Future Technology Research Division, Korea Institute of Science and Technology • Materials Science and Engineering, Seoul National University • Department of Metals and Materials Engineering, University of British Columbia, Vancouver, Canada Introduction • Biological application of DLC as a stent • General Bio application of DLC DLC for Wear Resistance Courtesy of A-san hospital (’04.7.) ● Electrolytic-polishing ○ liquid : A2 ○ 15V, 19flow, 30Sec ● Processing parameters ○ Ar cleaning : 3mTorr, -600Vb, 15min-60min ○ Si buffer layer - 20m Torr, 60% MFC - -200Vb, 2min 30sec-15min ○ Annealing : at room-400°C ● DLC deposition ○ R.F-PACVD ○ C6H6, -400Vb, 10mTorr, 11min Experimental condition Purpose • Estimated problem of DLC for bio application as a stent ○ Biomaterial : Stainless steel ○ Disadvantage of metal substrate as a biomaterial - wear debris : cause foreign body reaction, tissue reaction - harmful ion ( Cr+, Ni+) can occurrence - metal corrosion can induce bone resorption • Ar pre-cleaning Time & adhesion Experimental Results 20μm Ar -600Vb, 15min Ar -600Vb, 30min A direction of cracks followed the perpendicular against strain direction and spallation which seem to related to its slip band propagated with its shear stress Strain- Force curve of tensile test Ar -600Vb, 60min • Bias voltage & adhesion • Annealing & adhesion • Si buffer thickness & adhesion Summary • Stability of DLC films within 2% strain. However, Observed • crack occurrence from 3.8% strain. • A Relationship of adhesion depends on processing parameters. ◦ Improvement of adhesion with increasing Ar pre-cleaning time ◦ Enhancement of adhesion with increasing Bias voltage during Ar pre-cleaning. ◦ Increasing of adhesion with increasing Si buffer layer thickness ◦ Degradation of adhesion with increasing Bias voltage during Si buffer layer deposition ◦ Deterioration of adhesion with increasing Annealing temperature Ar -200Vb Ar -900Vb, No annealing Si -200Vb, 19nm • Evolution of spallation • ◦ Crack occurrence : Vertical of tensile direction • ◦ Spallation evolution direction : shear stress direction • Possibility of adhesion evaluation by tensile test. Ar -900Vb Ar -900Vb, 400°C annealing Si -200Vb, 84nm

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