Leidenfrost point and droplet dynamics on heated micropillar array surface

We studied the Leidenfrost Point (LFP) of a falling liquid droplet on various surfaces that were covered by micropillars. We used a Micro Electric Mechanical System to fabricate a bare smooth surface, and surfaces that had eight kinds of micropillar array. The pillar density was controlled by manipulating the distance between the micropillars. First, evaporation time of droplets of deionized water was measured under overheated condition (100-350 degrees C) to evaluate the LFP of the test samples. To analyze the LFP trend, the droplet dynamics were recorded at high speed, and their spreading diameter on impact, and the time that they took to rebound from the surface were measured. We then modelled the interaction between droplet and test samples and discussed the physical mechanism of the LFP change. We detected an optimal micropillar density at which the LFP was highest in this study. This study provides insights into the droplet impact and rebounding process on an overheated textured surface, and the resulting heat transfer. (C) 2019 Elsevier Ltd. All rights reserved.