Figure 4

The opening and closing mechanism of the siphon model. (a) Five consecutive images of the siphon model moving near the water-air interface. (b) Schematic illustration of the force balance between hydrostatic pressure (P h ) and Laplace pressure (P l ) . (c) Wettability of the siphon, especially the lobes part, after dying with surfactant. The white dashed line represents a positive curvature of gas bubble released from the spiracle.