An aerodynamic Leidenfrost droplet is faster than a cold Leidenfrost droplet

Place your bets! Which surface do you think will win in a race between two droplets down an incline, a Leidenfrost, or a superhydrophobic surface? Come find out as we examine the friction forces encountered by droplets moving on non-wetting surfaces, with a specific focus on droplets of varying viscosity traversing a heated superhydrophobic surface. We highlight and contrast the differences by comparing the observed dynamics with that of a droplet moving on a Glaco-coated superhydrophobic surface at room temperature (T = 22 ^oC) and Leidenfrost temperature (T = 300 ^oC). Spoiler alert, the droplet moving on a heated Glaco-coated surface, which exhibits a cold Leidenfrost effect, moves slower than the droplet moving on non-heated superhydrophobic surface, which exhibits an aerodynamic Leidenfrost effect. High-speed interferometric visualization shows that the droplet on a heated Glaco-coated superhydrophobic surface can develop instabilities within the vapor layer, resembling a Taylor-Saffmann instability and indicating additional viscous dissipation. Furthermore, these results uncover previously unexplored droplet dynamics and offer valuable insights into the dissipative mechanism at play for a droplet traversing a heated superhydrophobic surface