Polymer hydrophilicity and hydrophobicity induced by femtosecond laser direct irradiation

Controlled modification of surface wettability of polymethyl methacrylate (PMMA) was achieved by irradiation of PMMA surface with femtosecond laser pulses at various laser fluences and focus distances. Fluences from 0.40 to 2.1 J/cm(2) produced a hydrophobic surface and 2.1 to 52.7 J/cm(2) (maximum investigated) produced a hydrophilic surface. Fluences less than 0.31 J/cm(2) had no effect on the wettability of the raw PMMA. This change in wettability was caused dominantly by laser induced chemical structure modification and not by a change in surface roughness. (C) 2009 American Institute of Physics. [doi:10.1063/1.3232212]