Abstract
Drop motility at liquid surfaces is attracting growing interest because of its potential applications in microfluidics and artificial cell design. Here we report the unique highly ordered pattern that sets in when a millimeter-size drop of dichloromethane spreads on an aqueous substrate under the influence of surface tension, both phases containing a surfactant. Evaporation induces a Marangoni flow that forces the development of a marked rim at the periphery of the spreading film. At some point this rim breaks up, giving rise to a ring of droplets, which modifies the aqueous phase properties in such a way that the film recoils. The process repeats itself, yielding regular large-amplitude pulsations. Wrinkles form at the film surface due to an evaporative instability. During the dewetting stage, they emit equally spaced radial strings of droplets which, combined with those previously expelled from the rim, make the top view of the system resemble a flower.
Highlights
Drop motility at liquid surfaces is attracting growing interest because of its potential applications in microfluidics and artificial cell design
We consider a simple system made of a drop of dichloromethane (DCM) deposited on an aqueous substrate, with cetyltrimethylammonium bromide (CTAB), a common cationic surfactant[21], present in both phases with the same concentration
A 5.6 μl DCM drop is deposited onto a 25 ml aqueous phase filling a 7 cm Petri dish
Summary
Drop motility at liquid surfaces is attracting growing interest because of its potential applications in microfluidics and artificial cell design. The initial spreading results from the relative interfacial properties of the sub-phase and drop, the latter being either surface-active[13], or containing[14] or producing[15] (through a chemical reaction) a surfactant, which is transferred to the supporting phase This transfer modifies the surface properties in the drop surroundings, leading to its recoil. The expanding stage may sometimes repeat, provided that the drop environment has been regenerated, making it possible to restore the initial interfacial conditions Few examples of such a behavior have been reported so far, the very first mention being for a cetyl alcohol drop on water[16]. The drop and the film that surrounds it up to the rim exhibit the most regular large-amplitude pulsations ever reported This film undergoes a very rich succession of hydrodynamic events (spreading, rim and wrinkles formation, rim break-up, and droplets ejection) with a degree of organization culminating during film recoil. Specific measurements and theoretical analysis enable us to establish the main characteristics of several of these steps and reveal the underlying driving physical mechanisms
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
