# Dynamics of a Camphoric Acid boat at the air-water interface

## TL;DR

This study investigates the self-propulsion behaviors of a camphoric acid-loaded gel boat at the air-water interface, revealing three distinct motion modes driven by surface tension differences, unified under a common framework.

## Contribution

It demonstrates that the harmonic, steady, and relaxation oscillation modes of the camphoric acid boat are interconnected and can be controlled via surface tension manipulation.

## Key findings

- Identified three distinct motion modes of the c-boat.
- Showed all modes originate from surface tension differences.
- Controlled modes using SDS to alter surface tension.

## Abstract

We report experiments on an agarose gel tablet loaded with camphoric acid (c-boat) set into self-motion by interfacial tension gradients at the air-water interface. We observe three distinct modes of c-boat motion: harmonic mode where the c-boat speed oscillates sinusoidally in time, a steady mode where the c-boat maintains constant speed, and a relaxation oscillation mode where the c-boat maintains near-zero speed between sudden jumps in speed and position at regular time intervals. Whereas all three modes have been separately reported before in different systems, we show they belong to a common description. Through control of the air-water surface tension with Sodium Dodecyl Sulfate (SDS), we experimentally deduce the three self-propulsive modes result from surface tension difference between Camphoric Acid (CA) and the ambient surroundings.