Surface modification of UHMWPE with infrared femtosecond laser

Abstract

Ultra-high-molecular-weight polyethylene (UHMWPE) is a polymer with mechanical and corrosion properties, which make it appropriate for using in biomedical devices such as hip and knee prostheses. The surface morphology and chemistry of UHMWPE influence its biocompatibility. A laser with wavelength at 1027nm delivering 450fs pulses at a repetition rate of 1kHz is used to modify the surface of UHMWPE samples with 0.45μm root mean square surface roughness. Micrometric resolution is achieved with the use of a focusing lens of 0.25NA and pulse energies of few microjoules.The study focuses in the influence of different pulse energies and pulse overlaps on the laser-induced surface roughness and ablation yield. Confocal microscopy is used to characterize changes in the morphology of the irradiated surfaces, and their chemical structure is analyzed by attenuated total reflectance infrared and Raman spectroscopies.The roughness increases as the pulse energy increases until it reaches a maximum. The ablation yield increases with the pulse energy and pulse overlap. However, the ablation yield per pulse is lower for higher pulse overlap. Pulses of 6μJ have the highest ablation efficiency. Infrared and Raman spectra of samples irradiated with low energy pulses are similar to those of the pristine sample. However, some CC and CO bonds can be detected after irradiation with the highest pulse energies.