Abstract
The wettability of glass surfaces is controlled by laser irradiation. The quantity of the remaining
hydrophobic group on the glass surface depends on the laser power and the scan speed, and the quantity
determines the contact angle of the glass from 110 to 40º. This modification has long-time stability and
is unaccompanied by surface damages, cracks, morphology changes, or degradations of transparency.
This local wettability control achieves a surface-flow channel on the glass substrate without grooves.
The local hydrophilic area can be regarded as a channel because the water droplet selectively flows into
the area. In addition, the contact angle’s gradation gives the droplet driving force toward a lower contact
angle area. Modification of the surface-flow channel is expected to enable printing micro-fluidic systems
on glass.
