Abstract
In this paper, we propose a new buoyancy control device utilizing the phase change of material between liquid and solid states. In general, when solid material is heated above its melting point, the material melts and changes to a liquid state having a larger volume. This causes an increase in buoyancy. One hypothesis claims that sperm whales change their buoyancy based on the same principle. We have already developed a buoyancy control device utilizing rubber stretch to change a volume. In this paper, we build another device based on the same principle with a two step piston mechanism. First, we investigated which material is suitable for this device and find that lard oil is more suitable than paraffin wax, which was used in the previous version of the buoyancy control device. Then, we build a buoyancy control device with the mechanism and confirm its usefulness through experimental results
