Evaporation-induced freezing dynamics of droplets levitated in acoustic field

TL;DR

This study investigates how evaporation causes freezing in levitated cyclohexane droplets, combining experimental visualization with theoretical modeling to understand phase transition dynamics in a containerless system.

Contribution

The paper introduces a new experimental and theoretical framework for analyzing evaporation-induced freezing of droplets in acoustic levitation.

Findings

Evaporation initiates surface freezing of levitated cyclohexane droplets.

A heat transfer coefficient model predicts the onset of freezing.

Experimental data validate the theoretical prediction method.

Abstract

This paper presents the evaporation-induced freezing dynamics of pure cyclohexane droplets levitated via acoustic levitation. Acoustic levitation has attracted considerable attention across various fields owing to its potential to create lab-in-a-drop systems. While droplet evaporation is a fundamental physicochemical process in such a platform, the freezing of droplets induced by evaporation has been sparsely explored experimentally. For pure cyclohexane, the rapid evaporation of levitated droplets initiated freezing at the droplet surface. To better understand this evaporation-induced freezing process, the evaporation behavior of the levitated cyclohexane droplets was visualized and quantified using a high-speed camera and an infrared camera. According to the obtained experimental data, the evaporative heat transfer characteristics of the droplets were identified with theoretical models. Using the derived heat transfer coefficient, a mathematical prediction method for the onset of freezing was proposed and validated with the experimental data. These experimental findings offer valuable insights into the phase transition process and its potential physicochemical applications in a containerless environment.