LCVD coating biomaterials

The three unique and important features of type A LCVD nanofilm—imperturbable surface (Chapter 29), nanoscale molecular sieve (Chapter 34), and new surface state of material (Chapter 24) make LCVD coating an ideal tool in preparation of biomaterials. It should be reiterated that these three features of LCVD films are limited to type A plasma polymers described in Chapter 8, and type B plasma polymers should be excluded in LCVD coatings for biomaterials based on the concept of imperturbable surface. The particularly important aspect is that the LCVD nanofilm becomes the new surface state of the substrate material, i.e., it is not just a coating placed on the surface. The first and second features describe the nature of the new surface state. 

LCVD coating for biomaterials is the neutral approach illustrated by the athrombogenic surface. The advantage of the neutral approach in biomaterials is not well recognized, simply because finding such a surface in the domains beyond the imperturbable surfaces of type A plasma polymers is extremely difficult. 

The three key features of LCVD coating ideally suited for biomaterial surface, and the important balance between the bulk properties and the surface properties, could be best illustrated by examples of nanofilms of methane plasma polymer on a contact lens made of polydimethylsiloxane elastomer. Hence, some details of processing factors and their influence on the overall properties of the product are described in the following sections. 

The surface is a crucially important factor of biomaterial, and without an appropriate biocompatibility the biomaterial could not function. On the other hand, the bulk properties of materials are equally important in the use of biomaterials. An opaque material cannot be used in vision correction, and soft flexible materials cannot be used in bone reinforcement. The probability of finding a material that fulfills all requirements in physical and chemical bulk properties for a biomaterial application and whose surface properties are just right for a specific application is very close to zero, if not absolutely zero. From this point of view, all biomaterials should be surface treated to cope with the biocompatibility. However, if the surface treatment alters the bulk properties, it defeats the purpose. In this sense, tunable LCVD nanofilm coating that causes the minimal effect on the bulk material is the best tool available in the domain of biomaterials. 

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