Core release dynamics of double-emulsion droplets induced by temperature gradient

Abstract

The thermocapillary-driven core release of double-emulsion droplets offers advantages such as simplicity in implementation and a broad range of applications, providing unique strengths in the field of core component release. However, the characteristics and mechanisms related to thermocapillary-driven core release were still unknown. This article employed the Volume of Fluid method to investigate the core release characteristics of double-emulsion droplets driven by thermocapillary. The range of Marangoni (Ma) numbers is from 10 to 500. The results indicate that effective control of the migration and release dynamics of double-emulsion droplets can be achieved through viscosity regulation, which induces the obvious difference between the two types of double-emulsion droplets. The regulation of both viscosity and surface tension is efficient in controlling the release type of the core. A phase diagram distinguishing between one-off and two-off release types is presented. Additionally, by characterizing dimensionless numbers, a formula for the characteristic release time of double-emulsion droplets is derived. The current study contributes to achieving precise control of double-emulsion droplets, expanding the scope of applications for double-emulsion droplets and establishing a fundamental groundwork for subsequent investigations into the release methods of double-emulsion droplets driven by thermocapillary.