Candle Soot is a Low-cost Alternative for Water Repelling Surfaces?

The ubiquitous phenomenon of superhydrophobic surfaces repelling water droplets is exploited in numerous industrial processes which include self-cleaning and thermal management. However, the longer fabrication time and higher cost of the robust and stable superhydrophobic surfaces have remained their Achilles heel. Interestingly, candle soot-based superhydrophobic surfaces can be an economical alternative to tackle the earlier issue, even when produced using the simplest methods like manual flame deposition. We have evaluated the non-wetting behavior of such carbon-based fractal surfaces using a wide range of droplet impact phenomena, which remain scarcely reported to date. The critical limit of the key events namely, rebounding, contact time, impalement transition and splashing dynamics in different impact conditions have been plotted in a working regime map. The most remarkable observation is the absence of the partial rebound regime during the impact of water droplets, unlike several existing superhydrophobic surfaces. Similarly, the contact time of impacting water droplets even shows a similar scale to that of Leidenfrost droplets for a wide range of conditions. There is a need for further investigation of the non-wetting behavior of carbon soot-based surfaces in the future.