continued application of the laser energy 32 results in the formation of a ridge 48 comprising coalesced nodes 46 interconnected by fibrils 6 valleys 50 are formed having a microstructure of nodes 4 interconnected by fibrils 6 on valley floor 51 irregularly shaped gnarled node structures 44 remain in the valleys 50 shown in fig4 e is a partial cross sectional view of an expanded ptfe surface after processing according to the present invention shown are ridges 48 valleys 50 coalesced node clusters 46 and the distorted crooked gnarled node structures 44 laser energy for the present invention should be generated by an unfocused laser beam delivering sufficient energy to the ptfe surface to cause ptfe surface alteration in the manner described specifically it is preferred to use a co 2 laser with a wavelength output of about 10 6 microns other lasers such as eximer yag ruby etc may also be suitable for use with the present invention it is preferred that the laser beam is u201c unfocused u201d so that energy is delivered over a wider path than a fully focused beam the preferred beam width at contact with the surface is less than about 1 mm to 3 mm or more with the most preferred width being between about 1 5 and 3 mm the amount of power delivered is a function of the speed of the laser beam 39 s passage over the ptfe surface for slow laser treatment for instance at a movement of about 10 inches 25 4 cm per minute.