Parylene Coating Blog by Diamond-MT

Lubricious Coatings

Posted by Sean Horn on Fri, Jul 14, 2017 @ 07:37 AM

Contributing to good performance for internal medical appliances, lubricity is a conformal coating’s ability to lower operational friction that might retard its function and endanger patient health.  Lubricious coatings offer essential protection for appliances like cardiac-assist devices (CADs), catheters, elastomers, guidewires, and stents.  Compared to an uncoated device, lubricious films can reduce frictional forces by more than 90%, dramatically decreasing potential harm caused by excessive insertion-force or internal puncture damage.  This relative ease of use is important for implants and similar devices that require navigation throughout the patient’s vascular system or other internal structure; otherwise, patients can suffer from abrasion generated between the device surface and blood vessel walls. 

Coefficient of Surface Friction

The degree of physical resistance a device demonstrates is numerically expressed by a coating’s coefficient of friction (µ), which quantifies:

Static friction (µs) occurs when an object moves across a stationary surface; kinetic friction (µk) results for two objects simultaneously in motion, moving across each other.  Conformal coatings are used in both circumstances, especially for medical implants with moving MEMS/nano-tech components.

Where higher-level surface lubricity is sought, lower µ-values are the objective; they signify lessened frictional resistance, minimizing non-release, dry-sticking challenges that interfere with devices’ performance.  For instance, a µ-value of 1 indicates an equal quantity of force is needed to either lift an object, or slide it across a level surface; these calculations compare an object’s weight to the total force required to make it move.  Most everyday objects and materials have a coefficient between 0 and 1; values closer to 1 are not feasible for medical purposes.  For medical devices, a µ-value:

  • ranging from 0.01 to 0.1 is ideal,
  • but remains difficult to achieve
  • for application to the expansive degree of metallic and polymeric substrates used for medical appliances,
  • which require highly-specified levels of abrasion resistance and non-thrombogenic properties,
  • in addition to biocompatibility and lubricity.

Appropriate safety standards also need to be met.

Much depends on the materials comprising the touching surfaces.  Conformal coatings like Teflon (PTFE) and parylene, which provide high-level lubricity, maintain that level for a prolonged operational duration, making them very useful for specialized medical applications.

Properties of Reliable Coating Lubricity

Lubricated surfaces have lower levels of friction.  Wet hydrophilic coatings amass water as a source of lubricity, applied by liquid methods such as dipping or spraying the film substance onto substrates.  Applied to catheters or guidewires, they temporarily minimize development of thrombosis.  However, their lubricious function decreases with time, dissociating or dissolving from the matrix surface, leaving particulates in tissue or the bloodstream, endangering patient health.  Thus, they are less reliable long-term than hydrophobic coatings   

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Tags: parylene, parylene properties, Medical conformal coatings, medical device coating, lubricious coatings

Liquid Teflon vs Parylene

Posted by Sean Horn on Fri, Dec 30, 2016 @ 07:46 AM

           Conformal coatings are surface treatments applied to a wide range of products and devices used for aerospace, automotive, biomedical, consumer, military and numerous other purposes.  Their primary objective is providing a protective film that supports a selected device’s ease of use, operating function, and service life, through an exceptional variety of working environments.  Liquid Teflon (PTFE) and parylene are two of the more widely used hydrophobic conformal coatings. 

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Tags: Medical conformal coatings, medical parylene, medical parylene uses, teflon, medical device coating, ptfe

Comparing Lubricious Coatings

Posted by Sean Horn on Fri, Dec 23, 2016 @ 07:47 AM

Selection of the material used to coat a medical device is very influenced by the operational environment it will encounter when implanted in the body.  Pertinent operational/performance factors typically include:

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Tags: medical parylene, medical devices, medical device coating

Parylene Protects Stents

Posted by Sean Horn on Fri, Dec 16, 2016 @ 07:48 AM

Biocompatible parylene conformal coatings provide superior protection for medical stents.  They represent an enabling technology consistently applied to medical devices of all types for 35 years, to diminish problems stemming from surface microporosity and consequent biofluid corrosion after implant.  Providing a reliable barrier to chemicals and moisture, parylene’s static and dynamic coefficients of friction are comparable to those of Teflon.

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Tags: parylene, Medical conformal coatings, medical parylene, medical parylene uses, medical devices, bio-medical, medical device coating

Parylene Coating Nitinol

Posted by Sean Horn on Fri, Dec 09, 2016 @ 07:24 AM

A metal alloy of nickel (Ni) and titanium (Ti), nitinol (NiTi) exhibits the properties of shape memory and superelasticity, which make it very useful for adaptation to conformal coatings.  However, like parylene, nitinol is often difficult and expensive to produce; the extreme reactivity of the alloy’s titanium component requires exceptionally tight compositional control during combination and manufacture.  

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Tags: parylene, medical parylene, medical devices, medical device coating

Is Parylene Safe?

Posted by Sean Horn on Fri, Aug 12, 2016 @ 07:30 AM

Application of parylene’s xylylene monomer employs a chemical vapor deposition (CVD) process implemented under a vacuum.  Unlike wet coating application methods – brushing, dipping, spraying, etc. – parylene CVD is not line-of-sight.  Because the vaporous monomer envelopes all sides of the assembly being coated, appropriate process control allows vacuum deposition of an entirely conformal coating, one that penetrates deep into any crevices, rivulets, or sharp edges and points that exist on the assembly’s surface.  The resultant parylene film is insulating, ultra-thin, and pinhole-free, exhibiting superior protective barrier qualities and very low moisture permeability.

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Tags: parylene, parylene deposition, parylene uniformity, medical parylene, medical device coating, parylene safety

Five Common Causes of Parylene Failure

Posted by Sean Horn on Fri, Aug 05, 2016 @ 08:00 AM

Parylene Conformal Coatings

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Tags: parylene, parylene adhesion, parylene disadvantages, medical device coating, parylene delamination, parylene issues

Implantable Devices and Parylene

Posted by Sean Horn on Fri, Dec 18, 2015 @ 08:40 AM

Implantable Medical Devices and the Uses of Parylene

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Tags: parylene, implantable devices, medical devices, medical device coating

What is Parylene used for?

Posted by Sean Horn on Fri, Sep 18, 2015 @ 09:08 AM

Parylene and Conformal Coatings 

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Tags: parylene, MEMS, medical device coating, COTS

Improving Bio-Compatibility with Parylene

Posted by Sean Horn on Fri, Sep 11, 2015 @ 08:39 AM

Parylene Bio-compatibility

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Tags: parylene, bio-medical, medical device coating