Non-stick droplets

Recently, many ways (sometimes inspired by nature) for achieving super-hydrophobic surfaces have been proposed in the literature. On such surfaces, water makes a contact angle close to 180°, which produces spectacular properties: droplets do not stick and the surfaces repel water, which bounces when thrown on them. Here, we describe a way to reach the maximum possible contact angle, namely 180°, by texturing the liquid surface instead of the solid one, as it is done for super-hydrophobic solids. It is shown that the contact between such a marble and the solid on which it is deposited is very small, which dramatically reduces the friction when these marbles move. High speeds are thus observed. Together with the fact that the marbles roll as they move, this produces spectacular changes in shape. But the marbles resist to these changes, which can be of interest for practical applications in microfluidics.