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

Metal–Organic Framework “Swimmers” with Energy-Efficient Autonomous Motility

“…This trend can be ascribed to the fact that while the mass of the particles increases as L 2 , the flux of the fuel emitted onto the interface from the sides of the particles scales only as L . At the same time, the larger particles propel themselves continuously for longer times; for instance, 3 mm squares start exhibiting intermittent motions at ∼300 s, whereas 11 mm squares move continuously for >900 s. This effect, observed previously for camphor boats, , can be explained by smaller particles running out of chemical fuel earlier than larger ones: When the fuel is delivered onto the interface very slowly, the particle stops moving, “waits” until accumulation of fresh fuel reaches a certain critical value, and then expands this fuel rapidly during intermittent motion until the next stop point, after which the above scenario repeats (for more thorough discussion of this mechanism, see refs and ).…”

“…Examples include droplets (sometimes tactic − ) driven by interfacial reactions, segmented nanorods , powered by the catalytic decomposition of H 2 O 2 , micromotors fueled by catalytic reactions, − light, , electric, , and magnetic , fields, polymer capsules, , exfoliating particles, as well as numerous forms of the so-called camphor boats based on gels − or polymers . In particular, camphor boats spread surface-active chemicals onto the interface at which they rest, thus establishing surface tension gradients, which, in turn, set up convective Marangoni flows in the surrounding fluid. − These flows then power the boats to perform different types of motion (continuous, oscillatory, or intermittent , ) and, if many boats are present, can drive formation of dynamic structures, including open-lattice arrays or swarms in which smaller particles assemble behind and follow larger “leaders” . Recent progress in the synthesis of metal–organic framework, NOF, crystals and films of appreciable dimensions ( i.e.…”

“…24 In particular, camphor boats spread surface-active chemicals onto the interface at which they rest, thus establishing surface tension gradients, which, in turn, set up convective Marangoni flows in the surrounding fluid. 25−27 These flows then power the boats to perform different types of motion (continuous, 28 oscillatory, 21 or intermittent 29,30 ) and, if many boats are present, can drive formation of dynamic structures, including open-lattice arrays 31 or swarms in which smaller particles assemble behind and follow larger "leaders". 32 Recent progress in the synthesis of metal−organic framework, NOF, crystals 33 and films 34 of appreciable dimensions (i.e., larger than microscopic crystallites) has prompted interest in these materials also acting as autonomous moversthis idea rests on the assumption that MOFs' highly ordered porous structures could regulate release of surface-active molecules and thus control the ensuing motion.…”

Autonomously Moving Colloidal Objects that Resemble Living Matter

“…Nakata et al successfully extracted many dynamical modes from autonomous motions of camphor and camphor floats on a water surface [73][74][75][76]. This principle of camphor motion is illustrated in Figure 16 and is undoubtedly driven by a surface tension gradient.…”

Quasi-elastic Laser Scattering for Measuring Inhomogeneous Interfacial Tension in Non-equilibrium Phenomena with Convective Flows

“…Such systems, called dissipative dynamic systems, occur, for example, under macroscopic agitation, during the flip-motion of a liquid/liquid interface, [3][4][5][6][7][8] or when objects display various modes of motion. [9][10][11][12][13][14][15][16][17][18] The BelousovZhabotinsky (BZ) reaction, which generates chemical oscillations in a bulk material, also produces sophisticated spatio-temporal patterns in an unstirred system. [19][20][21][22][23][24][25] Interfacial tension and its spatial distribution are key properties in these non-equilibrium and non-linear phenomena, since they govern molecular transport.…”