Modulating Leidenfrost-like Prompt Jumping of Sessile Droplets on Microstructured Surfaces NPformat

TL;DR

This study demonstrates low-temperature modulation of Leidenfrost-like droplet jumping on microstructured surfaces by controlling vapor bubble growth modes, enabling rapid droplet removal at temperatures much lower than traditional Leidenfrost conditions.

Contribution

It introduces a novel method to induce and control droplet jumping at significantly lower temperatures using micropillar structures to manipulate vapor bubble dynamics.

Findings

Droplets jump within 1.33 ms at 130°C, much lower than traditional Leidenfrost temperatures.

Droplet jumping behavior can be tuned by adjusting pillar heights and thermal boundary layers.

Distinct bubble growth modes lead to different droplet jumping behaviors, enabling controlled droplet removal.

Abstract

The Leidenfrost effect, namely the levitation and hovering of liquid drops on hot solid surfaces, generally requires a sufficiently high substrate temperature to activate the intense liquid vaporization. Here we report the agile modulations of Leidenfrost-like prompt jumping of sessile water microdroplets on micropillared surfaces at a remarkably mitigated temperature. Compared to traditional Leidenfrost effect occurring above 230 {\deg}C, the fin-array-like micropillars enables Wenzel-state water microdroplets to levitate and jump off within 1.33 ms at an unprecedently low temperature of 130 {\deg}C by triggering the inertia-controlled growth of individual vapor bubbles at the droplet base. We demonstrate that droplet jumping, resulting from the momentum interactions between the expanding vapor bubble and the droplet, can be deftly modulated by simply tailoring the thermal boundary layer thickness via pillar heights, which acts to regulate the bubble expansion between the inertia-controlled mode and the heat-transfer-limited mode. Intriguingly, the two bubble growth modes give rise to distinct droplet jumping behaviors characterized by constant velocity and constant energy schemes, respectively. This strategy allows the facile purging of wetting liquid drops on rough or structured surfaces in a controlled manner, inspiring promising applications in rapid removal of fouling even settled in surface cavities.