Camphor Disk Research Articles

Synchronized motion of the water surfaces around two fixed camphor disks

The synchronized motion of the water surfaces in contact with two fixed camphor disks was investigated. When the distance between the two camphor disks was greater than 8 mm, the shapes of the water surfaces at the bottoms of the disks oscillated independently. In contrast, synchronized oscillation was observed when the distance was shorter than 7 mm. Depending on the distance, the nature of the Marangoni convection and the difference in the shape of the meniscus changed. The convection was numerically simulated based on the Navier–Stokes equation. The mechanism of synchronization is discussed in relation to the rolling structure of the Marangoni convection.

Mode-Switching of the Self-Motion of a Camphor Boat Depending on the Diffusion Distance of Camphor Molecules

We demonstrated mode-switching of self-motion coupled with diffusion of molecules at a solid/liquid interface. A camphor boat moved spontaneously on water and the mode of self-motion depended on the setup of the boat. When a camphor disk was connected to the center of a larger plastic plate, intermittent motion (alternating between rest and rapid motion) was observed. When the position of the camphor disk was changed from the center to one of its edges, the period of intermittent motion decreased, and intermittent motion changed to continuous motion. The features of this self-motion and mode-switching were qualitatively reproduced by a numerical calculation using a mathematical model that incorporates the distribution of camphor molecules at the solid/liquid interface.

Self-Motion of a Camphor Disk on an Aqueous Phase Depending on the Alkyl Chain Length of Sulfate Surfactants

A change in the mode of self-motion was investigated for a camphor disk on water upon the addition of sulfate surfactants with alkyl chains of different lengths as a simple autonomous system. With an increase in the concentration of surfactant with a longer alkyl chain (number of hydrocarbons: 14 or 16), two mode changes (continuous --> intermittent (alternating between motion and rest) --> no motion) were observed. With an increase in the concentration of surfactant with a shorter alkyl chain (number of hydrocarbon: 10 or 12), four mode changes (continuous --> intermittent --> continuous --> intermittent --> no motion) were observed. These two types of mode changes are discussed in relation to the solubility of the surfactant and camphor in the water phase and the surface tension of the surfactant, camphor, and a mixture of surfactant and camphor as the driving force of motion.

Intermittent motion of a camphor float depending on the nature of the float surface on water

The periodic motion of a camphor float on water was investigated as a simple example of an autonomous motor. When a camphor disk that was connected to the center of a larger plastic disk was floated on water, intermittent motion (alternating between rest and rapid motion) was observed. The period of intermittent motion decreased with an increase in the hydrophobicity of the plastic film, which depended on the density of carbon powder that had been adhered to the plastic film with a laser printer. When a square plastic film with half-hydrophobic and half-hydrophilic surfaces was used as the camphor float, the direction of intermittent motion was mostly toward the hydrophilic side. These phenomena are discussed in relation to the diffusion of camphor molecules at the film/water interface and the surface tension around the film as the driving force.

Oscillation of a water surface in contact with a fixed camphor disk

The oscillatory motion of a water surface in contact with a fixed camphor disk was investigated. A periodic change in the contact length of the upheld water was synchronized with the changes in the force working on the disk. The period of the oscillation changed depending on the surface tension and the surface area of the water phase. The mechanism of oscillation is discussed in relation to the kinetics of the camphor molecular layer on the water surface and the change in the driving force working on the contact line due to the surface tension and the Marangoni flow.

Chemo-mechanical energy transduction through interfacial instability

Clarifying the mechanism of chemo-mechanical energy transduction under isothermal conditions has been an important goal in nonlinear science. We have approached this problem by creating experimental model systems and proposing a new hypothesis. In this article, we describe some chemically nonequilibrium systems such as the Belousov–Zhabotinsky (BZ) reaction, a camphor disk on water, a mixture of water and alcohol, and a reactive droplet on a glass plate. In these systems, various kinds of mechanical motion are driven by nonequilibricity. These results stress the importance of the boundary condition.

A theoretical and experimental study on the unidirectional motion of a camphor disk

The self-sustaining motion of a camphor disk in an annular water channel was investigated. Unidirectional motion along the water channel is maintained after a local perturbation is applied to the system. Introduction of a partition into the channel changes the unidirectional motion into back-and-forth motion. To clarify the nature of the driving force that moves the settling camphor disk, the dependence of the velocity of the disk on the viscosity of the aqueous phase was measured. The experimental results are discussed in relation to the distribution of the camphor layer around the disk as the driving force. The nature of the self-motion is qualitatively reproduced by numerical computations using a mathematical model that incorporates the distribution of the camphor layer around the disk and the viscosity of the aqueous phase. Furthermore, the existence and stability of the unidirectional motion of the camphor disk depending on the viscosity of the aqueous phase are analyzed numerically.

Self-motion of a camphor disk coupled with convection

The self-motion of a camphor disk on water was investigated both experimentally and theoretically. When the camphor disk moved along a one-dimensional water chamber, a convective flow was observed around the disk and the magnitude of convection decreased with an increase in the velocity of camphor motion. The camphor disk exhibited a characteristic motion that depended on the shape of the base of the chamber. The nature of the self-motion was reproduced by a numerical simulation that included the surface tension of the camphor layer as the driving force and Marangoni convection induced by the difference in surface tension around the camphor disk.

Intermittent motion of a camphor float

Abstract The periodic motion of a camphor float on water was investigated as a simple example of an autonomous motor. When a camphor disk was placed on a water surface, a periodic change in the surface tension at the camphor solid/water interface was observed which was synchronized with a change in the meniscus. When a camphor disk that was connected to a larger plastic disk was floated on a water surface, intermittent motion (alternating between rest and rapid motion) was observed. The duration of the rest period increased with an increase in the diameter of the plastic disk. When the resting camphor started to move, a camphor layer developed on the side opposite the direction of the motion. The nature of this intermittent motion is discussed in relation to the state of the camphor disk with the surface tension of the camphor layer as the driving force.

The unification of quantum gravity

The spontaneous motion of an elliptic camphor particle floating on water is studied theoretically and experimentally. Considering a mathematical model for the motion of an elliptic camphor particle in a two-dimensional space, we first investigate the asymptotic solutions with numerical computation. We then introduce a small parameter ε into the definition of the particle shape, which represents an elliptic deformation from a circular shape and, by means of perturbation theory, we analytically calculate the travelling solution to within O(ε). The results show that short-axis-directed travelling solutions primarily bifurcate from stationary solutions and that long-axis-directed ones are secondary which means that elliptic camphor particles are easier to move in the short-axis direction. Furthermore, we show that rotating solutions bifurcate from stationary solutions and that the bifurcation point changes with O(ε2), which suggests that elliptic camphor disks easily exhibit translational motion, rather than rotational, within the small deformation. Finally, our theoretical suggestions are confirmed by an experiment.

ChemInform Abstract: A Method for Preparation of Unsupported Sol‐Gel Thin Films

Abstractis developed which involves the spin‐coating of a polished camphor disk with a viscous colloidal sol.