Convectional, sedimentation, and drying dissipative structures of black tea in the presence and absence of cream

Convectional, sedimentation, and drying dissipative structures of black tea with and without cream were studied in a tea cup, a cover glass, a watch glass and a glass dish on macroscopic and microscopic scales. The convectional patterns were vigorous and irregular at the initial stage but soon highly distorted Bernard cells grew. The global integrated flows of the tea particles coated with cream at the air–suspension interface were observed vaguely from the central area toward outside edge at the initial stage in a tea cup and a large watch glass, but the flow direction turned oppositely from the outside to the central area. At the similar time, the short and few spoke lines appeared at the outside edge and grew long toward the central area. Then, the cooperative formation of clusters and bundles of the spoke lines took place at the middle and final convectional stages, and then the dynamic sedimentation patterns appeared. The drying patterns of tea with and without cream were composed of the broad ring at the outside edge and a round hill accompanied sometimes with the bundles of spoke lines. These features are consistent with those of suspensions of non-spherical particles. The pinning effect is not always supported by this work, but importance of the gravitational and Marangoni convectional flows is proposed instead. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Convectional and sedimentation dissipative patterns of Miso soup

Convectional and sedimentation dissipative patterns of Miso soup, one of the traditional Japanese soups, were observed in a Miso soup bowl, a green tea Ochawan (cup), a glass cup, a large glass bowl, and a large watch glass. When Miso soup was set in the substrates, the distorted Benard cells were soon observed after the initial irregular circulations, and the holes grew large at the cross points of the neighboring three Benard cells. The global integrated flow direction of convections at the liquid surface was from the center area toward the outside edge during the periods of formation of the distorted Benard cells. Meanwhile, the reversal of the global flow direction, from outward to inward, at the liquid surface took place. Furthermore, the inward flow at the surface, i.e., the outward flow at the bottom, was accompanied with the broad ring-like sedimentation patterns. The most plausible kinetic scheme of the change in the convectional patterns is proposed in this work.     

Convectional, sedimentation, and drying dissipative structures of ethanol suspension of colloidal silica (110 nm in diameter) spheres

Convectional, sedimentation, and drying dissipative structural patterns formed in the course of drying ethanol suspensions of colloidal silica spheres (110 nm in diameter) were studied in a glass dish and a watch glass. Vigorous cell convectional flow was observed with the naked eye, and the patterns changed dynamically with time. Broad-ring-like sedimentation patterns were observed in the suspension state just before the suspension was dried up, and the principal macroscopic patterns of the drying patterns were also broad-ring, though the colorful and fine microscopic structures were observed from optical microscopy.     

Convectional,sedimentation, and drying dissipative patterns of colloidal crystals of poly (methyl methacrylate) spheres on a cover glass

Direct observation of the convectional dissipative patterns was successful during the course of dryness of colloidal crystals of poly (methyl methacrylate) spheres on a cover glass. Formation processes of the convectional patterns of spoke-like lines were observed as a function of sphere size and also sphere concentration. During dryness of the suspensions, the brilliant iridescent colors changed beautifully. Macro- and microscopic drying patterns and thickness profiles of the dried film were observed. Sharp broad rings were observed especially at low sphere concentrations. The water evaporation accompanied with the convectional flow of water and the colloidal spheres played an important role for these dissipative structure formation.     

Convectional,sedimentation and drying dissipative patterns of colloidal crystals of poly(methyl methacrylate) spheres on a watch glass

Direct observation of the convectional dissipative patterns at room temperature was successful on a cover glass during the course of dryness of colloidal crystals of poly(methyl methacrylate) colloidal spheres. Formation processes of the convectional patterns of spoke-like lines were observed as a function of sphere size and also sphere concentration. During dryness of the suspensions, the brilliant iridescent colors changed beautifully. Macroscopic and microscopic drying patterns of the dried film were observed. Multiple broad ring-like patterns were observed especially at low sphere concentrations. The water evaporation accompanied with the convectional flow of water and the colloidal spheres played an important role for the dissipative structure formation.     

Sedimentation and drying dissipative patterns of binary suspensions of colloidal silica spheres having different sizes

The sedimentation and drying dissipative structural patterns were formed during the course of drying binary mixtures among colloidal silica spheres of 183 nm, 305 nm, and 1.205 μm in diameter in aqueous suspension on a watch glass, a glass dish, and a cover glass, respectively. The broad ring-like sedimentation patterns were formed within several hours in suspension state for all the substrates used. Colorful macroscopic broad ring-like drying patterns were formed for the three substrates. In a watch glass, macroscopic drying patterns were composed of the outer and inner layers of small and large spheres, respectively. The two colored layers were ascribed to the Bragg diffractions of light by the dried colloidal crystals of the corresponding spheres. The width ratio of the layers changed in proportion to the mixing ratio of each spheres. In a glass dish, wave-like macroscopic drying patterns were observed in the intermediate areas between the outside edges of the broad ring and the inner wall of the cell. On a cover glass, the sphere mixing ratios were analyzed from the widths of the drying broad rings of the small spheres at the outside edge. High and distinct broad rings of small spheres and the low and vague broad one formed at the outer edges and in the inner area, respectively. Drying dissipative pattern was clarified to be one of the novel analysis techniques of colloidal size in binary colloidal mixtures.     

Sedimentation and drying dissipative patterns of colloidal crystals of poly(methyl methacrylate) spheres in a glass dish

In a series of our studies on the dissipative structure formation, this work focused on the sedimentation and drying patterns of colloidal crystals of poly(methyl methacrylate) colloidal spheres with different sizes (100, 200, 300, and 1,000 nm in diameter) in a glass dish. During the course of dryness, the brilliant iridescent colors changed. Drying frontier grew from the central area of the cell toward the outside edge. Macroscopic and microscopic drying patterns of the resulting film from dried colloidal suspensions showed outer and inner broad rings. Size of the outer rings increased with increasing sphere concentration but did not altered sphere size, while these factors affected the inner ring size. These observations do not support the pinning effect proposed by Deegan et al.     

Sedimentation and drying dissipative patterns of colloidal silica (305 nm in diameter) suspensions in a glass dish and a watch glass

Sedimentation and drying dissipative structural patterns formed in the course of drying colloidal silica spheres (305 nm in diameter) in aqueous suspension have been studied in a glass dish and a watch glass. The broad ring sedimentation patterns formed within several tenth minutes in suspension state by the convectional flow of water and colloidal spheres. The sedimentary spheres always moved by the convectional flow of water, and the broad ring patterns became sharp with time. The width of the broad rings was sensitive to the change in the room temperature and/or humidity. In other words, the patterns became sharp or vague when the room parameters decreased or increased. Colorful macroscopic drying structures were composed of a broad ring and the wave-formed patterns. Iridescent colored fine patterns formed in the solidification processes on the bases of the sedimentation patterns. Beautiful drying patterns were observed for the suspension mixtures of CS300 and NaCl, and were different from the structures of CS300 or NaCl individuals, which support the synchronous cooperative interactions between the colloidal spheres and the salt.     

Sedimentation and drying dissipative structures of green tea

Sedimentation and drying dissipative patterns formed in the course of drying green tea (Ocha) have been studied in tea cup (Ochawan), glass dish, polystyrene dish, and watch glass. The broad-ring patterns are formed within several tens of minutes in suspension state by the convectional flow of water and colloidal particles of green tea (7 μm in mean size and 5 μm in its dispersion from the mean size). Formation of the broad-ring patterns is retarded when a tea cup is covered with a watch glass, which demonstrates the important role of the convectional flow of tea particles and water induced by the evaporation of water at the air-suspension interface under the gravity. The sedimentary particles are suspended above the substrate plate and always move by the convectional flow of water. The broad-ring patterns become sharp just before the solidification occurs. The broad rings are formed even in an inclined glass dish, though the rings are transformed slightly, which demonstrates the strong convectional flow of the particles. The drying broad rings and the microscopic fine structures are formed in the solidification processes on the bases of the convectional and sedimentation patterns in suspension state.     

Sedimentation and drying dissipative patterns of colloidal silica (560 nm in diameter) suspensions in a glass dish and a watch glass

The sedimentation and drying dissipative structural patterns formed during the course of drying colloidal silica spheres (CS550, 560 nm in diameter) in an aqueous suspension have been studied in a glass dish and a watch glass. Broad ring patterns were formed within 20 min in the suspension state by the convectional flow of the colloidal spheres and water. The sedimentary spheres always moved by the convectional flow of water, and the broad ring patterns became sharp with time. The sharpness of the broad rings was sensitive to the change in the room temperature and/or humidity. Colorful macroscopic structures were composed of the broad ring and wave-like patterns, and further colorful and beautiful microscopic fine patterns formed during the solidification processes based on the convectional and sedimentation structures. The drying patterns of the colloidal suspensions containing sodium chloride were different from the structures of CS550 or sodium chloride individuals, which support the synchronous cooperative interactions between the colloidal spheres and the salts.     

Sedimentation and drying dissipative structures of colloidal silica (1.2 μm in diameter) suspensions in a watch glass

Sedimentation and drying dissipative structural patterns formed in the course of drying aqueous suspensions of colloidal silica spheres (1.2 μm in diameter) were observed in the various sizes of watch glasses. The macroscopic broad ring patterns were formed on the inner inclined watch glass in suspension state within a short time after suspension was set. The important role of the convectional flow of water and colloidal spheres for the pattern formation is supported. The influence of sodium chloride was also studied. It was clarified that the sedimentary spheres move toward upper and outer edges along the inclined cell wall by the cell convection and hence the patterns are formed by the balancing between the outside movement and the downward sedimentation of the spheres. Beautiful microscopic drying patterns were also observed from the optical microscopy.     

Sedimentation and drying dissipative structures of colloidal silica (1.2 μm in diameter) suspensions in a glass dish and a polystyrene dish

Sedimentation and drying dissipative structural patterns formed in the course of drying colloidal silica spheres (1.2 μm in diameter) in aqueous suspension have been studied in a glass dish and a polystyrene dish. The broad ring patterns are formed within a short time in suspension state by the convection flow of water and colloidal spheres. The broad ring patterns are not formed when a dish is covered with a cap, which demonstrates the important role of the convectional flow of silica spheres and water accompanied with the evaporation of water on the air-suspension interface. The sedimentary spheres always move by the convectional flow of water, and the broad ring patterns became sharp with time. Broad ring and microscopic fine structures are formed in the solidification processes on the bases of the convectional and sedimentation patterns. Drying patterns of the colloidal suspensions containing sodium chloride are star-like ones, which strongly supports the synchronous cooperative interactions between the salt and colloidal spheres.     

Kinetic aspects in the drying dissipative crack patterns of colloidal crystals

Kinetics of the dissipative structure formation in the course of drying the colloidal crystals of silica spheres (103 nm in diameter) in aqueous deionized suspension on a rinsed cover glass has been studied by the close-up video observation. The patterns of the broad ring of the hill accumulated with the spheres coexisted with the many spoke-like cracks. The characteristic convection flow of the spheres and the interactions between the spheres and substrate were important for the pattern formation. Cracks formed suddenly in the course of drying along the outside edge first, then toward the center, and stopped around the middle point between the outside edges and the frontier of suspension area. The further growth of the cracks took place at the adjacent place of the previous crack side by side and cooperatively. After the fast formation of these cooperative spoke-like cracks was completed, then all the crack lines further developed very slowly and simultaneously toward the center with the similar rate as that of the movement of the drying frontier of the suspension area toward center. Rates of the fast and slow modes of crack formation were 6.2 mm/s and 0.0098 mm/s, respectively, at the sphere concentration of 0.033 in volume fraction.     

Dissipative structures formed in the course of drying the colloidal crystals of silica spheres on a cover glass

Macroscopic and microscopic dissipative structural patterns formed in the course of drying the deionized aqueous colloidal crystal suspensions of silica spheres (diameter: 103 nm) on a cover glass have been observed. Spoke-like and ring-like patterns are formed in the macroscopic scale; the former is the crack in the sphere film and the latter is the hill accumulated with spheres formed around the outside edge. The neighbored inter-spoke angle, thickness of the film, and other morphological parameters have been discussed as a function of sphere concentration, concentration of sodium chloride, and the inclined angle of the cover glass. Fractal patterns of the mud cracks are observed in the microscopic scale. Capillary forces between spheres at the air-liquid surface and the relative rates between the water flow at the drying front and the convection flow of spheres are important for the pattern formation. Electronic Publication     

Drying dissipative patterns of dyes in ethyl alcohol on a cover glass

Drying dissipative structural patterns formed in the course of drying ethyl alcohol solutions of rhodamine 6G, uranine, 7-hydroxy coumarin, and 7-amino-4-(trifluoro methyl)-coumarin are studied on a cover glass. The macroscopic broad ring patterns form for all the solutions examined, which supported importance of the convectional flow of ethyl alcohol and dye solutes. Dried area increases as dye concentration increases above the critical dye concentration. Microscopic fine patterns including street-like, needle-like, and flower-like crystal structures are formed in the solidification processes. Change in the functional side group moieties of the dyes gives the strong effect on the microscopic drying patterns; even the main chemical structures are same. Kinetic aspect of the drying patterns is studied.     

Drying dissipative patterns of the colloidal crystals of silica spheres in an dc-electric field

Drying dissipative structural patterns of the colloidal crystals of silica spheres were studied under an dc-electric field. Platinum plate electrodes of anode and cathode were set on a cover glass. The broad hills accumulated with the spheres were observed at the outer edges of the dried film without and also with the electric fields. The column-like structures were formed by the electric flux, and movement of the spheres took place toward anode. The dried film kept colloidal crystal structure, where the nearest-neighbored spheres contact each other more compactly in the areas closer to the anode. Drying times needed for the complete dryness of the suspensions decreased as the strength of the electric field increased. Addition of sodium chloride to the suspensions retarded the movement of spheres toward the anode substantially.     

Drying dissipative patterns of colloidal crystals of silica spheres in organic solvents

Drying dissipative structural patterns formed in the course of drying colloidal crystals of silica spheres (110 nm in diameter) in water, methyl alcohol, ethyl alcohol, 1-propyl alcohol, diethyl ether, and in the mixtures of ethyl alcohol with the other solvents above have been studied on a cover glass. The macroscopic broad rings were formed in the outside edges of the dried film for all the solvents examined. Furthermore, much distinct broad rings appeared in the inner area when the solvents were ethyl alcohol, methyl alcohol, and their mixtures. Profiles of the thickness of the dried films were sensitive to the organic solvents and explained well with changes in the surface tensions, boiling points, and viscosities of the solvents. The macroscopic and microscopic spoke-like crack patterns formed. The drying area (or the drying time) increased (or decreased) as the surface tension of the solvent decreased. However, the absolute values of these drying parameters are determined also by the boiling points of the solvents. Importance of the fundamental properties of the solvents is supported in addition to the characteristics of colloidal particles in the drying dissipative pattern formation.     

Drying dissipative structures of aqueous solution of poly(ethylene glycol) on a cover glass, a watch glass, and a glass dish

Drying dissipative structures of aqueous solution of poly(ethylene glycol) (PEG) of molecular weights ranging from 200 to 3,500,000 were studied on a cover glass, a watch glass, and a glass dish on macroscopic and microscopic scales. Any convectional and sedimentation patterns did not appear during the course of drying the PEG solutions. Several important findings on the drying patterns are reported. Firstly, the crystalline structures of the dried film changed from hedrites to spherulites as the molecular weight and/or concentration of PEG increased. Secondly, lamellae were formed along the ring patterns especially at high concentrations and high molecular weights. The coupled crystalline patterns of the spherulites and the lamellae were observed in a watch glass along the ring structures, supporting the important role of the convection by the gravity during the course of dryness. The coupled patterns were difficult to be formed on a cover glass and a glass dish, except at the outside edge of the dried film. Thirdly, the size of the broad ring at the outside edge of the dried film especially on a cover glass and a watch glass increased sharply as the molecular weight increased and also as the polymer concentration increased. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Dissipative structures formed in the course of drying an aqueous solution of poly(allylamine hydrochloride) on a cover glass

Macroscopic and microscopic dissipative structural patterns formed in the course of drying a deionized aqueous solution of cationic polyelectrolyte, poly(allylamine hydrochloride) on a cover glass have been observed. Drying times range from 40 min at 45 °C to 450 min at 5 °C, and are insensitive to the polymer concentration. Pattern area shrinks toward the center at the low polymer concentrations, and increases as the concentration increases. A macroscopic broad ring pattern, where the polymer accumulates densely, forms in many cases. Beautiful fractal patterns are observed at the microscopic scale. The fractal dimension increases from 1.2 to 1.6 as polymer concentration increases from 10^-6 monoM to 10^-2 monoM. The relative rates between the water flow at the drying front and the convection flow of water accompanying the movement of polymer are important for the macroscopic and microscopic pattern formation.     

Drying dissipative patterns of aqueous solutions of simple electrolytes and their binary mixtures on a cover glass

The drying dissipative patterns of aqueous solutions of simple electrolytes, KCl, NaCl, CaCl₂, and LaCl₃, were observed on a cover glass. The macroscopic broad rings were formed at the outside edge of the drying film area, which shrunk from the initial solution area especially at low salt concentrations. The drying area and the broad ring size decreased as the salt concentration decreased. The microscopic block-like and dendritic cross-like patterns were observed for all the salts. Size of single crystals dried on a cover glass increased as salt concentration increased. The drying patterns of the binary mixtures of the salts were also observed. Size of the broad ring increased sharply by mixing. The microscopic patterns were, on the other hand, insensitive to the mixing.