Temperature-induced switchable interfacial interactions on slippery surfaces for controllable liquid manipulation

Recently, responsive slippery surfaces with controllable liquid droplet sliding have attracted interest due to their promise for applications in liquid transportation, microfluidics, microreactors, biomedicine and beyond. Controllable liquid sliding is closely related to regulatable interfacial interactions. However, investigations on the interfacial interactions that occur as a droplet slides on a responsive slippery surface are lacking. Herein, we directly detect the interfacial friction forces and adhesion forces between a liquid droplet and a temperature-responsive slippery surface by using atomic force microscopy and analyze the changes of intermolecular hydrogen bonds between droplet and lubricant by using molecular dynamics simulation. The results show that (i) the liquid sliding behavior on the slippery surface can be smartly controlled by increasing/decreasing the temperature; (ii) the interfacial friction forces and adhesion forces reversibly switch at high and low temperatures, which is the reason for controllable liquid sliding; and (iii) the nature of the switchable interfacial forces and controllable liquid sliding on the temperature-responsive slippery surface is attributed to changes in intermolecular interactions. This work would provide a way to understand the nature of controllable liquid motion on smart-responsive slippery surfaces in terms of intermolecular interactions between a droplet and the surface.