Biological Applications Of Diamondlike Carbons

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Diamond-like carbons (DLC) is a carbon material, which in fact is not like crystalline diamond, not as hard, and is virtually amorphous. Because its microstructure allows the incorporation of other species such as hydrogen, nitrogen, silicon, sulfur, tungsten, titanium, and silver, the properties of DLC can be tailored far more readily than those of diamond.32 DLC is also a potential material for biological and biomedical applications due to its high hardness, low friction coefficient, high wear and corrosion resistance, chemical inertness, high electrical resistivity, infrared-transparency, high refractive index, excellent smoothness, and good biocompatibility.33 DLC can be produced by a number of techniques such as radio frequency plasma enhanced chemical vapor deposition,34 ion plating,35 pulsed laser deposition,36 magnetron sputtering.37

For biomedical application, DLC-coated materials have been shown successfully to be applied for metal and plastic joint replacements. Figure 8.27 (Roy, 2007) shows the DLC coated ultrahigh

Figure 8.27. A C:H coated head and UHMWPE acetabular surface of a hip joint by radio frequency plasma chemical vapor deposition. Source: From Ref. 33.

molecular weight polyethylene (UHMWPE) surface of a hip joint. Figure 8.28 shows the Ankle joint coated with DLC.38

Another application of DLC is to make DLC-coated stents. A stent is a metal tube that is inserted permanently into an artery, which helps to open an artery so that blood can flow through it. Figure 8.29 from shows a biodiamond stent of Plasmachem.33 They used a DLC coating made by plasma-induced cold deposition technique to coat the inside and outside of their stainless 316L stents.

Recently, Fu and coworkers designed a TiNi/DLC microcage.39 The fingers of the microcage closed/opened through the shape memory effect depending on temperature. Figure 8.30 shows the schematic drawing of the bimorph TiNi/DLC microfinger structures. Figure 8.31 shows the closing of a five-finger

Figure 8.28. Ankle joint with both parts coated with DLC (talar component left picture, tibial component right picture). Source: Pictures from M. I. L. SA. From Ref. 38.
Figure 8.29. A biodiamond stent of Plasmachem. Source: From Ref. 33.
Figure 8.30. Schematic drawing of bimorph TiNi/DLC microfinger structures: (a) top view; (b) cross-section view after bending up. (c) illustration of bending angular and displacement. Source: From Ref. 39.
Figure 8.31. Optical microscopy images showing the closing of a five-finger microcage during heating (during cooling the process is reversed; beam length: 150 ^m): (a) 20°C, (b) 55°C, (c) 65°C, and (d) 80°C. Source: From Ref. 39.

microcage during heating using optical microscopy. Figure 8.32 shows SEM picture of a microcage capturing a micro-polymer ball. Further cell culture experiments showed that there is no cytotoxicity of TiNi/DLC. This microcage can be used as microgrippers for biological applications such as biopsy, tissue

Figure 8.32. SEM picture of a microcage capturing a micro-polymer ball. Source: From Ref. 39.

sampling, cell manipulation, nerve repair, and minimal-invasive

surgery.39

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