Green self-propelling swimmer driven by rain droplets

Abstract

The existing self-propelling methods have the limitations of chemical reaction, emission of toxics and additional auxiliary devices, high cost, low durability, and low propelling force and velocity, making them difficult for apply in practice. To overcome these limitations, we develop a green self-propelling swimmer composed of a superhydrophobic plate with a superhydrophilic slit on its sidewall. Water droplet touched with the slit easily and quickly pass through the slit and generate a water jet to propel the swimmer to spontaneously move. The propelling velocity, propelling time, propelling distance, and movement direction of the swimmer are programmable by adjusting the slit width, water droplet volume and the shape of the swimmer. Since the developed swimmer can easily capture the water droplet from rain as the fuel, our self-propelling method can also make full use of rain energy, effectively transfer the surface energy of rain droplets into mechanical energy, and easily realize the continuous movement in the rainy environment, showing remarkable application prospect in the collection and application of rain energy.