Surface treatment of silicate based glass: base Piranha treatment versus 193nm laser processing

Contact angle measurements of water on pathology grade borosilicate glass microscope slides before and after base piranha treatment are compared to treatment with 193nm laser irradiation. 193nm irradiation in the presence of hydrogen was also explored. Within experimental resolution, the observed changes in contact angle as a result of treatment either with base Piranha solution or with laser processing are identical. The contact angle, a, in both cases is reduced from a = (27 +/- 6)degrees to a = (8 +/- 3)degrees with treatment. However, for the piranha base method, there is an observed reversal over time either fully recovering or partially recovering within hours. By contrast, with laser processed, the increased surface wettability is retained with no change for more than 15 hours. In all cases, surface functionalisation, as measured by contact angle, with (3-mercaptopropyl) trimethoxysilane (MPTS) is found to be largely independent of any processing. We conclude that the method of contact angle as a means for qualitatively asserting improvements in attachment is unjustified.