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How Plasma Can Aid Catheter Manufacturing

Leading Supplier Of Instruments Systems And Technology, Henniker, Explains How Plasma Can Aid Catheter Manufacture

Catheter function and patient health rely on strict material biocompatibility in order to prevent pathogen introduction and propagation and to reduce instances of associated urological and vascular problems.

Plasma surface modification is proving to be a reliable and effective method for treating various component materials, and also finished devices, in order to minimise the potentially harmful side effects of catheter use.

Plasmas can be tailored to deliver surface properties including anti-fouling, anti-microbial and increased lubricity amongst others. They can achieve a range of desirable properties either directly by polymeric deposition or indirectly, by introducing intermediate functional layers prior to application of a final surface finish or coating.

Plasmas are not a lab curiosity. Plasma technology has been an important production tool for more than 30 years in the fabrication of microelectronic devices for example. Over this period, plasma technology has also permeated a much broader range of industries.

Its useful to define what a plasma is. Solid, liquid and gas are the three states of matter we are all familiar with. We can move between the states by adding or removing energy (eg heating/cooling). If we continue to add enough energy, gas molecules will become ionised (lose one or more electrons) and so carry a net positive charge. If enough molecules are ionised to effect the overall electrical characteristics of the gas the result is called a plasma. Plasmas are therefore quite rightly, often referred to as the fourth state of matter.

A plasma contains positive ions, electrons, neutral gas atoms or molecules, UV light and also excited gas atoms and molecules, which can carry a large amount of internal energy (plasmas glow because light is emitted as these excited neutral particles relax to a lower energy state). All of these components can interact with the surface during plasma treatment. By choosing the gas mixture, power, pressure etc we can quite precisely tune, or specify, the effects of the plasma treatment.

Many polymers used in catheter manufacture are chemically inert and cannot bond easily to other materials, displaying poor adhesion with inks, paint and glues. The reason for this is the absence of polar and reactive functional groups in their structure. Plasma surface activation renders many polymers receptive to other coatings. Oxygen is usually used as the process gas, however, many plasma activations can also be carried out with just ambient air.

Typical results for PU catheter materials that were modified by plasma treatment and then heparin coated revealed little or no protein binding after 30 days indwelling for example. In another example, hydrogel adhesion and friction reduction improvement figures up to 70% have been achieved by plasma treatment.


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