17:15 〜 18:45
[O07-P07] 樟脳船間の相互作用に起因した振動現象
★招待講演
キーワード：集団運動、樟脳、アクティブマター
There are many collective motions in our lives, such as schools of fish and birds, human crowds, and traffic jams. Collective motion has been studied in wide academic fields. Collective motions are also observed in chemical experiments. In the chemical experiments, a self-propelled particle, as a component of the collective motion, moves spontaneously due to the translation from a chemical energy to a kinetic energy. One of famous self-propelled particles is a camphor boat. Camphor has two characteristic properties. One is decreasing the surface tension. The other is that the camphor vapors in time development. Using these properties, camphor grains and camphor boats move spontaneously when the grains and the boats are placed on water. When the camphor grain is placed on water, the concentration of the camphor molecules around the camphor grain fluctuates. If the concentration is high, the surface tension decreases. Then, the force acts in the direction of the high surface tension (low concentration), and the camphor grain moves spontaneously.
The control of the concentration field allows the behavior of the camphor boat to be regulated. One way of controlling the concentration field is to design the camphor boat. For example, the camphor boat, where the camphor grain is attached with the plastic film, continues to move toward one direction (Fig. 1 (a)). The other example is a rotating camphor disk. An elliptical camphor disk is prepared, and the rotational axis is inserted into a hole in the center of the disk. The elliptical camphor disk continues to rotate on water, because the translational motion of the elliptical camphor disk is restricted by the axis. These camphor boats and disks, which demonstrate many movements, reproduce a variety of collective motions due to the interaction between the boats.
We proposed the experimental system to directly observe the collective motions resulting from the interaction between the boats. We designed the camphor boat in which two camphor grains were attached with the plastic film as shown in Fig. 1 (b). When we placed two kinds of camphor boats, as shown in Figs. 1 (a) and (b), on water in a one-dimensional container, the distance between two boats oscillated periodically due to the interaction between the two boats. The oscillation behavior bifurcated depending on the angle $\phi$ of the two camphor grains in Fig. 1 (b).
In this presentation, we showed our experimental results and discussed the mechanism of the oscillation behavior.
The control of the concentration field allows the behavior of the camphor boat to be regulated. One way of controlling the concentration field is to design the camphor boat. For example, the camphor boat, where the camphor grain is attached with the plastic film, continues to move toward one direction (Fig. 1 (a)). The other example is a rotating camphor disk. An elliptical camphor disk is prepared, and the rotational axis is inserted into a hole in the center of the disk. The elliptical camphor disk continues to rotate on water, because the translational motion of the elliptical camphor disk is restricted by the axis. These camphor boats and disks, which demonstrate many movements, reproduce a variety of collective motions due to the interaction between the boats.
We proposed the experimental system to directly observe the collective motions resulting from the interaction between the boats. We designed the camphor boat in which two camphor grains were attached with the plastic film as shown in Fig. 1 (b). When we placed two kinds of camphor boats, as shown in Figs. 1 (a) and (b), on water in a one-dimensional container, the distance between two boats oscillated periodically due to the interaction between the two boats. The oscillation behavior bifurcated depending on the angle $\phi$ of the two camphor grains in Fig. 1 (b).
In this presentation, we showed our experimental results and discussed the mechanism of the oscillation behavior.