The flow patterns of ink released by cuttlefish

Cuttlefish mix ink and water and release six ink patterns using the same funnel. Previous studies examine the chemical defense mechanisms of cuttlefish ink or intercommunication within the same species, which could benefit aquaculture. However, the physics of cuttlefish ink ejection remains poorly understood. Here we investigate how cuttlefish mix two liquids (water and ink) and jet various ink patterns with the same funnel. In this study, we observe live cuttlefish inking and mimic the process with a table-top. Cuttlefish's ink visualizes the flow field and demonstrates distinct characteristics. The rope-like ink could be laminar or transition flow, the ink blob is a vortex ring, and the puff ink is turbulent flow. The ejection velocity and the relative position between the ink and the involved water determine the patterns. The velocity of ink ejection determines how fast the pattern disperses. At low ejection velocities, the patterns remain for at least six seconds. At high velocities of ejection, the patterns disperse in one second. Our findings would advance liquid mixing methods applied in the pharmaceutical industry and inkjet technology.