Surface treatment for increasing the lubricity of catheters

 

Plasma treatment can be applied to catheters in order to reduce friction thanks to the its effect of enhancing the adhesion of lubricating coating such as Hydrogel.

 

Hereunder are described the results of two plasma-based treatment made by biomat engineering department as trials.

SAMPLES
Tests were performed on samples cut out from raw material used in manufacturing of catheters made of PU with different compositions (both aliphatic and ester PU).

TREATMENTS
The main features of the two types of surface treatments were the following :


treatment purpose expected effect
  • plasma of a reactive gas
modification of wettability increase of wettability avoids possible dry points of friction between catheter and vessel
  • plasma assisted coatings with Hydrogel in various concentrations
increase the adhesion of the Hydrogel coating thanks to a preliminary plasma treatment Hydrogel are based on a hydrophilic polymer which absorbs water from whichever aqueous medium increasing their volume and forming an insoluble layer with very low coefficient of friction.

TEST METHODS AND RESULTS
Samples were analysed and tested in order to verify the effects of surface modification both from the physical point of view and for its practical effect :

The enclosed graphics show the results of Contact Angle and Friction tests, and some considerations above those results are resumed hereunder:

plasma of a reactive gas Catheters' surfaces treated only with plasma show an increased wettability but poor results in reduction of friction. AFM analysis explained this behaviour showing a micro porosity which, while useful for the attachment of coating, makes it rougher and then justifies a slightly increased coefficient of friction.
plasma assisted coatings with Hydrogel in various concentrations Hydrogel coated surface gave brilliant results:
plasma treatment greatly improves Hydrogel adhesion and friction reduction ranges from 30 to 70 %.
AFM analysis shows a smooth surface.



CONCLUSIONS
Results show a dramatic reduction of friction in wet body tissue-like environment :
values from the friction test are reduced till 70% of raw tube ones, moreover standard deviation values of treated samples are generally lower than those of untreated samples, meaning that a more homogeneous surface is obtained.
Specific treatment can be developed for different materials and shapes.