Features

New materials and technological advances continue to proliferate the medtech industry at a rapid rate, and suppliers strive to offer innovative solutions to meet the demands of increasingly complex components and devices. A wide range of specialized materials are used today, and many of those materials are suitable for the intended finished use only after the application of a customized surface treatment. These treatments can result in reduced friction, improvement of haptic properties, the introduction of chemical functionalities, and improved medium resistance of the materials. To meet this growing demand, the supplier can utilize traditional coating methods, like wet chemicals, and state-of-the-art methods, such as plasma treatments, in order to alter the surface properties of medical components.

Fig. 1 – The plasma coating process.

Surface Modifications Allow Customization

Surface modifications allow a variety of unique customer needs to be addressed. For example, color coating is a surface modification that enables control of the base materials’ transparency and optical properties. Plasma treatment is another option that will reduce friction. Silicone itself has a high friction coefficient and a plasma treatment will modify its friction properties. This can improve silicone’s manufacturability (particularly in automated assembly lines) and its ability to be used in low-friction applications where gliding is necessary— such as with endoscopic catheters and the internal coating of flexible tubes used in cardiac pacemakers.

Surface modifications, such as plasma coating, directly influence the surface energy of a component. This allows control and adjustment of the hydrophilic properties. (See Figure 1) Plasma processes enable multiple functionalities to be implemented within a single process; for example, plasma enables a bioactive layer with good adhesion to be applied to a substrate in a single step. The surfaces are plasma coated, activated, or plasma etched using environmentally friendly processes.

A variety of component geometries can be altered with vacuum or atmospheric pressurized plasma, without solvent emissions or a time-consuming drying process. Small parts can be handled in bulk goods processes under a vacuum, while atmospheric pressure plasmas are well-suited for integration into existing process chains. Different systems for handling and coating are utilized depending on the specific geometry requirements of the component. (See Figure 2)

DLC

Fig. 2 – Plasma treatment of silicone molded parts results in an improved feel, and simplifies the production process.
Another newer surface coating technology is diamond-like carbon (DLC), which is biocompatible, amorphous, and can be produced by plasma-supported processes. It has a very low friction coefficient, good wear resistance, and a high layer of hardness resulting in a significantly higher stability for long-term implantable devices. By incorporating different chemical elements, DLC can be further adapted to special requirements. One example is an antibacterial effect, which can be achieved via the infusion of metal particles, such as silver.

Parylene Coatings

Parylene coatings are another medically approved surface coating technology. These coatings are hydrophobic, inert, transparent, non-porous, biocompatible, biostable, and have an outstanding barrier effect against moisture, chemicals, and gases. These coatings also have a high dielectric barrier effect. Four different types of Parylene are produced. The basic type is Parylene N (poly-para-xylene), which is characterized by a good gap penetration capability and a low friction coefficient. Parylene C has high chemical resistance and provides an excellent barrier effect against gases and moisture. Parylene D has long been used as a high-temperature Parylene due to its continuous use at a temperature of 100ºC. A new, fluorinated Parylene, Parylene HT®, is used at even higher temperatures (up to 350ºC) and has the highest gap penetration capability, a high UV resistance, and the lowest friction coefficient.

Conclusion

The medtech field continues to expand to meet the demands of new treatments and the complexity of devices that are part of those solutions. Unfortunately, there are no universal answers, it is important to find a production partner with the experience and technical capabilities to provide the right solution for your specialized needs. Surface engineering is one of the many areas in which suppliers can achieve continuous innovations to keep pace with the ever growing challenges of the healthcare industry.

This article was written by Lars Gerding, Corporate Technology Director, Helix Medical, Carpinteria, CA. For more information, Click Here.