The model, which uses kinematic closure, correctly estimates the maximum spread for different liquid combinations and temperature settings.

To create the compound drops, a suction technique is used. A needle filled with the shell fluid is dipped into a vial of the core liquid; the core liquid is drawn into the needle and the compound drop is ejected. The same method is used to produce drops with either water in oil or oil in water, enabling systematic testing of viscosity and surface tension effects.

Experiments show that the outer shell of the drop spreads in line with the Laan‑et‑al. (2014) scaling law (Figure 13a). Measurements of the maximum spread diameter match the model’s predictions closely for a range of viscosities and interfacial tensions.

The model treats the inner drop’s viscosity as an effective value that blends the core and shell viscosities. However, it deliberately leaves out secondary influences such as rim drag, transient boundary‑layer growth, and contact‑line friction. These simplifications mean that the model captures the dominant bulk dissipation but does not account for all boundary‑layer nuances.

The work also explores freezing behaviour on cold surfaces. By using liquids with different freezing points—e.g., water and hexadecane—researchers can freeze either one or both phases, producing distinct frozen patterns. The study illustrates how temperature and fluid composition together dictate the final droplet structure after impact.