Abstract:

A liquid jet can stably bounce off a sufficiently soft gel by following the contour of the dimple created upon impact. This new phenomenon is insensitive to the wetting properties of the gels and was observed for different liquids over a wide range of surface tensions, γ = 24 − 72 mN/m. In contrast, other jet rebound phenomena are typically sensitive to γ: only a high γ jet rebounds off a hard solid (e.g. superhydrophobic surface) and only a low γ jet bounces off a liquid bath. This is because an air layer must be stabilized between the two interfaces. For a soft gel, no air layer is necessary and the jet rebound remains stable even when there is direct liquid-gel contact.

Notes:

We would like to thank Prof. Michael Brenner, Prof. L. Mahadevan, and Prof. Kyoo-Chul Park for useful discussions. The work was supported partially by the ONR MURI Grant No. N00014-12-1-0875 (fluid dynamics studies) and the U.S. Department of Energy Award No. DE-SC0005247 (materials synthesis). We acknowledge support from the Harvard Materials Research Science and Engineering Center (MRSEC) through Grant No. DMR-1420570.

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