Hi All,

For a project, I am silanizing glass surfaces using PDMS-based microcontact printing stamps. I recently discovered that even when I don't dip my PDMS into ink, it still modifies the glass surface after contact. Somehow no ink PDMS touched areas become hydrophobic, but not as much as the areas that I use hydrophobic silane + PDMS. I confirmed this by contact angle measurements on the PDMS-contacted part of the glass.

I thought an empty stamp should be inert on the surface. Does anyone have any idea about what might be causing this surface modification? I am suspecting some kind of charge transfer from PDMS to the glass surface. Surprisingly, PDMS contacted surface does not recover back to normal after aging (>10 days), baking or various salt washes too.