Spiral Thermal Waves Generated by Self-Propelled Camphor Boats

TL;DR

This paper reports the observation of spiral thermal surface waves generated by self-propelled camphor boats, highlighting the roles of soluto-capillarity and thermo-capillarity in their formation and dynamics.

Contribution

It introduces the phenomenon of spiral thermal waves caused by self-propulsion of camphor boats and analyzes the underlying surface tension effects involved.

Findings

Spiral thermal waves are observed during dissolution and evaporation-guided self-propulsion.

Surface tension jumps due to soluto-capillarity are significantly larger than those from thermo-capillarity.

The spirals formed are Archimedean in shape.

Abstract

Spiral thermal surface waves arising from self-propulsion of the camphor-driven objects are reported. Spiral thermal waves were registered for the dissolution and evaporation-guided self-propulsion. Soluto-capillarity is accompanied by thermo-capillarity under self-propulsion of camphor boats. The jump in the surface tension due to the soluto-capillarity is much larger than that due to the thermo-capillarity. The observed thermal effect is related to the adsorption of camphor molecules at the water/vapor interface. The observed spirals are shaped as Archimedean ones.