Dual-Parallel-Channel Shape-Gradient Surfaces: Toward Oriented and Reversible Movement of Water Droplets

In this paper, we prepared dual-parallel-channel shape-gradient surfaces, on which water droplets can reversibly and orientedly move between two adjacent pools under the guidance of an external voltage. Furthermore, it is found that the motion speed is governed by several parameters, including bath condition, gradient angle, and the working voltage. In this self-transportation process of water droplets, the external voltage works like a traffic light, which can give moving, stopping, turning and straight-going signals to the Water droplets.