Unidirectional motion of a camphor disk on water forced by interactions between surface camphor concentration and dynamically changing boundaries

Abstract

We study the motion of a camphor disk on the water surface in a system with flexible boundaries.The boundaries can be dynamically modified by non-uniform surface tension resulting from the nonhomogeneous surface concentration of the camphor molecules dissipated by the disk. We investigate the geometry of the boundaries that forces unidirectional motion of the disk. The studied system can be regarded as a signal diode if the presence or absence of a camphor disk at a specific point is interpreted as the binary TRUE and FALSE variables. The diode can be incorporated into more complex devices, like a ring that imposes unidirectional rotation of camphor disks.

Spreading dynamics of reactive surfactants driven by Marangoni convection

“…Self-propulsion of Marangoni surfers is accompanied by a flow in the aqueous phase. The flow contributes to the interactions between particles [18][19][20][21] or with the boundaries of the system [22][23][24][25]. Both the individual and collective dynamics that emerge are extremely rich and have not been fully elucidated yet [26][27][28].…”

Rotational motion of a camphor disk in a circular region

“…In other words, a camphor particle releases its repellants (camphor molecules) and moves to the region with less repellent concentration. The camphor-water system is so simple that various geometries can be realized [21][22][23][24][25][26][27][28][29][30][31][32][33]. For example, the size of the water chamber can be one of the parameters which can affect the motion of the camphor disk [21,22].…”