Spreading dynamics of functional droplets

Spreading dynamics of functional droplets on flat substrates has been carefully studied. The spreading profiles correspond with the lubricant microstructures. Such correspondence indicates that functional lubricant molecules may transform from a bi-polymer structure to a layering structure during the spreading processes. The molecule movements are demonstrated to include flow-down, surface migration and fill-in processes. Especially, single functional molecule movement is tracked to reveal the detailed microscopic mechanism. The molecule movement is demonstrated to be significantly hindered by the hydrogen bonds among functional end groups. During flow-down process, the single molecule partly breaks the hydrogen bonds. As one end group of the molecule has arrived at the substrates, the other drags other molecules in droplets to flow-down. During surface migration process, the single molecule moves on the substrates combined with other molecules through the hydrogen bonds.