Low friction coating on vein catheter

A method of coating a substrate surface with boric acid comprising:

• providing a substrate surface;
• providing a solution of a boric acid forming compound and a polar solvent;
• applying the solution to the substrate surface;
• and
• allowing the solvent to evaporate leaving an at least partly coherent coating of boric acid on the surface.

A vein catheter device comprising a housing, a catheter tubing and a cannula, wherein

• the housing has a first end and a second end arranged along a central axis and an opening at the first end of the axis;
• the catheter tubing has a first end and a second end, and wherein the first end is mounted to the housing at the second end of the housing such that when the cannula is in a loading position the cannula is inserted through the opening of the housing into the catheter tubing;
• the cannula has an inner surface and an outer surface, wherein the length of the cannula is such that it extends beyond the second end of the catheter tubing when the cannula is in the loading position;
• and wherein the outer surface of the cannula is at least partly coated with crystal sheets of boric acid.