Different Transportations Of Water Droplets By Adjusting The Wetting Of The Path

The directional transportation of droplet on solid surfaces is essential in a wide range of engineering applications.It is convenient to guide liquid droplets in a given direction utilizing the gradient of wettability,by which the binding forces can be produced.In this paper,the experimental methods were used to study the transportation characteristics of droplets on surfaces with different surface energy.The main research results and innovations are as follows:(1)The droplet moving along the hydrophilic glass path on the horizontal superhydrophobic surface is barrier-free transportation,for droplets cannot derail from the track.Wind tunnel experimental system was used to test the influence of different track widths and different volumes of droplets on the critical velocity of droplet initiation.(2)The droplet moving along the V-shaped hydrophilic PMMA path is also called as recessive transportation.However,only on the deeper V-shaped hydrophilic PMMA path can the droplet be transported,and the depth of the V-shaped PMMA path strongly impact on many aspects of such transportation.(3)Compared with the mass-loss transportation of a droplet moving along hydrophilic paths on the horizontal superhydrophobic surface,the no-loss transportation by fabricating a hydrophobic path on the same surface was presented under the tangential wind.Through experimental exploration and theoretical analysis,the conditions of no-loss transportation of a droplet are mainly considered.We demonstrate that the lower(or upper)critical wind velocity,under which the droplet will start up on the path(or derail from the path),is determined by the width of the path,the length of the contact area in the direction parallel to the path,the drift angle between the path and wind direction as well as surface wettability of the pattern.Meanwhile,the no-loss transportation of water droplets along the desired path zigzagging on a superhydrophobic surface can be achieved steadily under an appropriate condition.(4)The droplet moving along the V-shaped superhydrophobic path is named as high-speed transportation,for the speed of movement is 1 to 2 orders of magnitude faster than other guidance methods,but it is not stable,only suiting for smaller droplets.Through experimental exploration and theoretical analysis,the conditions of no-loss transportation of a droplet are mainly considered.Gravity test system was used to test that how the different trajectory width and volume of droplets,as well as different pitch angle and yaw angle impact the lower(or upper)critical angle.