Dynamic behaviours and drying processes of water droplets impacting on superhydrophilic surfaces

The dynamic water contact performances and drying processes of two commercially available superhydrophilic coatings, QS200, used for glass antifogging, and QS3100, used for the self-cleaning of solar photovoltage panels, both with static contact angles near zero, have been evaluated. We investigated the drying behaviours of both statically and dynamically deposited water droplets on these two coatings by measuring droplet diameters and mass changes, and found that their dynamic water droplet behaviours were substantially different, although their static contact angles were essentially the same. The dynamic behaviour of water droplet impact on the QS200 coating was basically independent on the water droplet height (impact speed), while that on the QS3100 coating changed with droplet height. The drying times of droplets on the QS200 coating, both statically and dynamically deposited, were longer than on the QS3100 coating, although the initial droplet area on the QS200 coated surface was larger.