Parylene coatings

Parylene s use in the medical field is linked to electronics. Certain pacemaker manufacturers use it as a protective conformal coating on pacemaker circuitry (69). The coated circuitry is sealed in a metal can, so that the parylene coating serves only as a backup should the primary barrier leak. There is also interest in its use as an electrode insulation in the fabrication of miniature electrodes for long-term implantation to record or to stimulate neurons in the central or peripheral nervous system, as the "front end" of experimental neural prostheses (70). One report describes the 3-yr survival of functioning parylene-coated electrodes in the brain of a monkey (71). 

Dry Lubricant. The static and dynamic coefficients of friction for the parylenes are low and virtually the same. This feature is an advantage in the use of a parylene coating as a dry lubricant on the bearing surfaces of miniature stepping motors. Coating a threaded ferrite core significantly reduces the abrasion to coil forms (82). 

In a world increasingly conscious of the dangers of contact with chemicals, a process that is conducted within the walls of a vacuum chamber, such as the VDP process for parylene coatings, offers great advantages. Provided the vacuum pump exhaust is appropriately vented and suitable caution is observed in cleaning out the cold trap (trace products of the pyrolysis, which may possibly be dangerous, would collect here), the VDP parylene process has an inherently low potential for operator contact with hazardous chemicals. 

Kemet Flatkaps -parylene coatings pYLYLENE POLYMERS] (Supplement)... 

The parylcne process has certain similarities with vacuum metallizing. The principal distinction is that truly conformal parylene coatings are deposited even on complex, three-dimensional substrates, such as on sharp points and in hidden or recessed areas. Vacuum metallizing, on the other hand, is a line-of-sight coating technology. 

Micro-PCR is normally achieved in PC, Si, and glass but not PDMS because of its porosity. However, with a parylene (or poly-para-xylene) coating, problems of bubble formation, sample evaporation, and even protein adsorption are solved. In addition, no BSA or PEG additive is needed in the PCR mixture for dynamic coating because the parylene coating (4.5 pm thick) is hydrophobic. This can be... 

FIGURE 9.7 The contact angle of PDMS after various surface treatments (a) 3 h after 02 plasma treatment (28° C), (b) 48 h after 02 plasma treatment (70° C), (c) 144 h after 02 plasma treatment (90° C) and (d) parylene-coated PDMS (92° C)[1000]. Reprinted with permission from the Institute of Physics Publishing. 

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