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 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.     

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.     

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 silica (183 nm in diameter) suspensions in a glass dish and a watch glass

Convectional, sedimentation, and drying dissipative structural patterns formed during the course of drying aqueous colloidal crystals of silica spheres (183 nm in diameter) have been studied in a glass dish and a watch glass. Spoke-like convectional patterns were observed in a watch glass. The broad ring sedimentation patterns formed especially in a glass dish within 30–40 min in suspension state by the convectional flow of water and colloidal spheres. The macroscopic broad ring drying patterns formed both in a glass dish and a watch glass. The ratio of the broad ring size in a glass dish against the initial size of suspension, i.e., inner diameter of the glass dish, d _f/d _i, in this work, were compared with previous work of other silica spheres having sizes of 305 and 560 nm and 1.2 μm in diameter. The d _f/d _i values in a glass dish increased as sphere concentration increased, but were rather insensitive to colloidal size. The d _f/d _i values on a watch glass also increased as sphere concentration increased, and further increased as sphere size decreased. Segregation effect by sphere size in a watch glass takes place by the balancing between the upward convectional flow of spheres in the lower layers of the liquid and the downward sedimentation of spheres. Colorful microscopic drying patterns formed both in a glass dish and a watch glass.     

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.     

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 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 ternary mixtures of colloidal silica spheres having different sizes

The sedimentation and drying dissipative structural patterns were formed during the course of drying ternary mixtures of 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. The patterns were observed by closed-up pictures, metallurgical optical microscopy, 3D profile microscopy, reflection spectroscopy and AFM images. The concentrations of the three spheres ranged from 0.0023 to 0.0128 keeping the same concentrations for each spheres. Broad ring-like sedimentation patterns were formed within a short time in suspension state especially in a glass dish. In a watch glass, colorful three layered ring-like drying patterns were observed and composed of the outer, middle and inner layers of small, medium, and large spheres, respectively. The three colored segregated layers were formed by the balancing between the outward convectional flow and the inward sedimentation of spheres. In a glass dish, wave-like macroscopic drying patterns were observed in the intermediate areas between the outside edge of the broad ring at the central area and the inner wall of the cell especially at low sphere concentrations. The size of the broad ring at the central area increased as sphere concentration increased. On a cover glass, size segregation also took place, i.e., small, medium, and large spheres located at the outer, medium, and central areas, though these segregations were not so complete compared with those on a watch glass.     

Drying dissipative structures of spindle-shaped hematite particles coated with polymer brush

Macroscopic and microscopic drying patterns were observed on a cover glass, a watch glass, and a Petri glass dish during dryness of aqueous suspensions of spindle-shaped particles of hematite coated with polymer brush (SHB). Outer and inner broad rings formed and the spoke-lines appeared especially on a watch glass at the intermediate initial concentration of SHB. Cooperative drying processes of the convection, sedimentation, and solidification were supported also for the anisotropic particles. Most of the long axes of SHB particles distributed parallel to the substrate plane. There appeared the microscopic alignment of the several ten micrometers similar-sized aggregates composed of the SHB particles. The parallel and/or flower-like (or spoke-like) arrangements of SHB particles were observed in the scanning electron microscopy. Effective shape of SHB particles including the electrical double layers during the convection flow processes are deduced to be near spherical. However, the effective shape came to be spindle-like during the sedimentary and solidification processes by the thinning of the double layers. The distorted paralleled and/or flower-like alignments of SHB particles were observed in the dried film.     

Drying dissipative structures of Chinese black ink on a cover glass and in a dish

Macroscopic and microscopic dissipative structural patterns are formed in the course of drying a suspension of Chinese black ink on a cover glass and in a dish. The time for the drying and the pattern area increased as the particle concentration increased. The broad ring patterns of the hills accumulated with the particles formed around the outside edges on a macroscopic scale. The height and the width of the broad ring increased as the particle concentration increased. The spokelike patterns of the rims accumulated with particles were also formed on a macroscopic scale. Microscopic patterns of colloidal accumulation were observed over the whole region of the pattern area. Various types of convection cells were observed on a cover glass and in a dish at 25–80 °C. A time-resolved observation of the drying process was also made. The convections of water and the colloidal particles at different rates under gravity and the translational and rotational Brownian movement of the particles were important for the macroscopic pattern formation. Microscopic patterns were determined by the translational Brownian diffusion of the particles and the electrostatic and the hydrophobic interactions between the particles and/or between the particles and the cell wall in the course of the solidification of the particles.     

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.     

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.     

Drying dissipative structure of similar sized aggregates (1.5 μm in diameter) of nano-sized diamond particles (4 nm in diameter)

Macroscopic and microscopic drying patterns were observed on a cover glass, a watch glass, and a Petri glass dish during the course of dryness of aqueous suspensions of similar sized aggregates of diamonds (CD1), which formed from the deionization of the pre-particles of diamond 4 nm in diameter. Two kinds of macroscopic patterns, i.e., outer and inner broad rings, and spoke lines were formed. Cooperative drying processes of the convection, sedimentation, and solidification were clarified. Microscopic drying patterns showing the formation of very large dendritic aggregates from the CD1 particles were observed only when the excess amount of sodium chloride higher than 2 mM coexisted in the initial suspensions before dryness and further initial CD1 concentration is lower than 0.17 wt%.     

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.     

Drying dissipative structures of the thermosensitive gels of poly(N-isopropyl acrylamide) on a cover glass

Drying dissipative structural patterns of the thermosensitive gels of poly(N-isopropyl acrylamide) were studied on a cover glass. As the temperature of suspension and room rose from 25 to 50 °C, the small size of drying pattern area extended to the beautiful flickering spoke-like ones transitionally at the critical temperature ca. 35 °C. The principal patterns at 25 °C were the single or multiple broad rings of the hill accumulated with the gels. At 50 °C, on the other hand, the flickering spoke-like patterns were observed at the inner area of the broad ring especially at the gel concentrations higher than 1 × 10⁻³ g/ml. These observations support that the extended gels at low temperatures apt to associate weakly to each other, whereas the gels at high temperatures shrink and move rather freely with the convectional flow of water, though the very weak intergel attractions still remain. In the presence of sodium chloride at high temperatures, the cooperative patterns formed between the gel spheres and the salt. The gravitational and Marangoni convectional flow of the gels and the very weak interactions between the gels and substrate (cover glass) are important for the flickering spoke-like pattern formation.     

Inclusional association as studied by the drying dissipative structure. Part 1. Drying patterns of α-, β- and γ-cyclodextrin

Macroscopic and microscopic drying patterns were observed on a cover glass, a watch glass, and a Petri glass dish during the course of dryness of aqueous solutions of α-cyclodextrin (αCD), β-cyclodextrin (βCD), and γ-cyclodextrin (γCD), i.e., cone shape oligomers of polysaccharide. For all CD molecules, two kinds of macroscopic patterns, outside and inner broad rings and spoke lines formed. Multi-broad rings were formed for βCD in the inner region of the main broad ring at the outside edge especially at the high concentrations. Cooperative drying processes of the convection, sedimentation, and solidification were clarified. Microscopic drying patterns showing the formation of rod-like and/or sward-like crystals were observed mainly in the direction along the spoke lines. The microscopic patterns of βCD were similar to those of some of polysaccharides and polynucleotides the authors studied previously. α- and γ-cyclodextrins were slightly hygroscopic, and clear-cut drying patterns were not observed.     

Drying dissipative structures of thermo-sensitive gel spheres of poly(<Emphasis Type="Italic">N</Emphasis>-isopropylacrylamide) with low degree of cross-linking

Drying dissipative patterns of deionized suspensions (colloidal crystal state at high concentrations) of the thermo-sensitive gels of poly(N-isopropylacrylamide) with low degree of cross-linking of 0.5% (318 nm and 116 nm in the hydrodynamic diameter at 25 °C and 45 °C) were observed at 20 °C and 45 °C on a cover glass, a watch glass and a Petri glass dish. The broad rings were observed and their size decreased as micro-gel concentration decreased. Formation of the monodispersed agglomerated particles and their ordered arrays were observed. This work clarified the formation of the drying microscopic structures of (a) flickering ordered spoke-lines, (b) ordered rings, (c) net structure, and finally (d) lattice-like ordered structures of the agglomerated particles. The net and lattice structures formed more favorably at higher temperatures and/or higher degree of cross-linking of the gels. Importance of the convectional flow of the agglomerated particles during the drying processes is supported for the ordered array formation. The role of the electrical double layers around the agglomerated particles and the interaction of the particles with the substrate surfaces during dryness are also important for the ordering. The microscopic drying patterns of gel spheres were quite different from those of linear-type polymers and also from typical colloidal spheres, though the macroscopic patterns such as broad ring formation at the edges of the dried film were similar to each other.     

Drying dissipative structures of thermo-sensitive gel spheres of poly(<Emphasis Type="Italic">N</Emphasis>-isopropylacrylamide)

Drying dissipative patterns were observed at 25 °C, 33 °C, and 45 °C on a cover glass, a watch glass, and a Petri glass dish during the course of dryness of colloidal crystals of the thermo-sensitive gels of poly(N-isopropylacrylamide) (PNIPA). Two kinds of broad rings, i.e., transparent ring at the outside edge and the ring in the inner area from the edge, were observed. Sizes of the former were the same as those of the initial liquids irrespective of gel concentration, whereas sizes of the latter decreased as gel concentration decreased. These broad rings were composed mainly of the monomeric and the agglomerated gel particles, respectively. Formation of the monodispersed agglomerated particles and their ordered arrays in the inner area of the dried film were observed especially on a Petri glass dish and a watch glass. The important role of the electrical double layers formed around the agglomerated particles is supported for the ordering of the agglomerated particles. The essential differences in the drying patterns between PNIPA gel spheres and the typical colloidal particles did not appear.