Topography for enhancing droplet levitation on a heated surface

The levitation of a droplet occurs when there is sufficient gas cushion beneath the liquid surface. Previous studies have demonstrated that the combination of surface superhydrophobicity and heating can significantly reduce the temperature required for achieving a non-wetting state droplet, which is referred to as the cold Leidenfrost regime. In this study, we report observations of the non-wetting cold Leidenfrost regime of ethanol droplets on a micro-conical structured surface. We demonstrate an improvement in the levitation ability of a combined conical pillar and hole structure compared to a conical structure without pillar-hole topography. The unique topography of the conical pillar-hole structure induces a lower wetting force but a higher non-wetting force, resulting in better non-wetting properties. The increased ratio of the non-wetting force to the wetting force not only allows for the levitation of ethanol droplets but also results in the spontaneous jumping of a millimeter-scale pinned droplet. These findings provide valuable insights into the non-wetting properties of conical structures and contribute to the development of methods for maintaining a non-wetting state at lower temperatures.