Droplets at the air-liquid interface of immiscible liquids usually formpartially-submerged lens shapes (e.g. water on oil). In addition to thisstructure, we showed that droplets released from critical heights above thetarget liquid can sustain the impact and at the end maintain a sphericalball-shape configuration above the surface, despite undergoing largedeformation. Spherical drops are unstable and will transform into the lens modedue to slight disturbances. Precision dispensing needles with various tipdiameter sizes were used to release pendant drops of deionized water onto thesurface of fluorocarbon liquid (FC-43, 3M). A cubic relationship was foundbetween the nozzle tip diameter and the released droplet diameter. Drop impactwas recorded by a high speed camera at a rate of 2000 frames per second. Inorder for the water drops to sustain the impact and retain a sphericalconfiguration at the surface of the target liquid pool, it is required thatthey be of a critical size and be released from a certain height; otherwise thecommonly observed lens shape droplets will form at the surface.
展开▼
