Solidification and Ordering during Directional Drying of a Colloidal Dispersion

Goehring, Lucas; Clegg, William; Routh, Alexander F.

doi:10.1021/la100125v

Cited by 94 publications

(158 citation statements)

References 28 publications

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“…11). These changes were expressed as drying fronts, which propagated across the film at some speed v, as have been previously reported [3, 4,12,30,31]. Observing at one point, the transitions were seen as occurring at different times, as the fronts successively passed through the beam.…”

Section: Discussion Three Transitionsmentioning

confidence: 66%

“…The superficial fluid velocity should take a maximum, u 0 , at the aggregation front, and decrease slowly until stagnation at the pore opening front, over a distance, x d = vτ d . Assuming that x d is constant, then this mass balance is simply [12] …”

Section: The Solid Filmmentioning

confidence: 99%

“…Previous work has provided a robust description of the film formation processes during lateral drying [3, 4,9,12,13]. The general observation is that drying fronts sweep across the liquid film, starting from the edge and progressing toward the middle.…”

Section: Introductionmentioning

confidence: 99%

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Drying Dip-Coated Colloidal Films

Cabane

Sztucki

et al. 2011

Langmuir

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We present the results from a Small Angle X-ray Scattering (SAXS) study of lateral drying in thin films. The films, initially 10 µm thick, are cast by dip-coating a mica sheet in an aqueous silica dispersion (particle radius 8 nm, volume fraction φs = 0.14). During evaporation, a drying front sweeps across the film. An X-ray beam is focused on a selected spot of the film, and SAXS patterns are recorded at regular time intervals. As the film evaporates, SAXS spectra measure the ordering of particles, their volume fraction, the film thickness and the water content, and a video camera images the solid regions of the film, recognized through their scattering of light. We find that the colloidal dispersion is first concentrated to φs = 0.3, where the silica particles form a gel with repulsive interactions. Then the particles aggregate until they form a cohesive wet solid at φs = 0.68 ± 0.02. Further evaporation from the wet solid leads to evacuation of water from pores of the film, but leaves a residual water fraction φw = 0.16. The whole drying process is completed within three minutes. An important finding is that, in any spot (away from boundaries), the number of particles is conserved throughout this drying process, leading to the formation of a homogeneous deposit. This implies that no flow of particles occurs in our films during drying, a behavior distinct to that encountered in the iconic coffee-stain drying. It is argued that this type of evolution is associated with the formation of a transition region that propagates ahead of the drying front. In this region the gradient of osmotic pressure balances the drag force exerted on the particles by capillary flow toward the liquid-solid front. INTRODUCTIONCoatings are often made through deposition of liquid colloidal dispersions. Common examples are paints, anticorrosion coatings and ceramic coatings. In most cases, the dispersion is applied as a liquid film, and it changes into a solid film as a result of solvent evaporation. A variety of deposition patterns can be obtained, depending on the evaporation profile over the liquid film and on the flows taking place inside the deposit during drying [1][2][3][4][5][6][7]. The two extreme situations are as follows:(a) Homogeneous film formation: in the simplest case, there is no lateral flow through the liquid film, and all volatile components are evaporated locally. The number of particles at each point of the film is conserved throughout the drying process. Therefore the deposition of a uniform liquid colloidal film leads to a final solid film that has homogeneous composition, thickness and microstructure. Relatively homogeneous films can also be obtained through mechanisms where there is a moving liquid-solid boundary, and there is a flow of liquid phase near this boundary [8,9].(b) Coffee-ring: this process has also been extensively studied [1, 2]. In this situation a macroscopic flow throughout the liquid carries nearly all the particles to the fixed edges of the film, where they pack into a dense rim. At the end o...

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Section: Discussion Three Transitionsmentioning

confidence: 66%

Section: The Solid Filmmentioning

confidence: 99%

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Drying Dip-Coated Colloidal Films

Cabane

Sztucki

et al. 2011

Langmuir

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“…The lateral drying has been termed the coffee ring effect, after the original work by Deegan et al [5]. The lateral drying also results in pressure gradients and film cracking [6,7].…”

Section: Introductionmentioning

confidence: 99%

Autostratification in Drying Colloidal Dispersions: Experimental Investigations

et al. 2012

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In films cast from a colloidal dispersion comprised of two particle sizes, we experimentally examine the distribution of particles normal to the substrate. The particle concentrations at various positions in the film are determined through atomic force microscopy and NMR profiling. The results are compared to a previously derived diffusional model. Evidence for diffusional driven stratification is found, but the importance of other flows is also highlighted. The conditions that enhance particle stratification are found to be a colloidally stable dispersion, low initial volume fractions, a low concentration of the stratifying particle and for the Peclet numbers of the two components to straddle unity.

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“…In particular, the larger 1 mm trace widths were observed to yield a change in the colour shade at the trace edges ( Figure 9). Goehring et al [54] reported on such a phenomenon in the drying of colloidal dispersions. In particular, they observed a series of fronts when a colloidal suspension dries directionally, with distinct regions separating the liquid dispersion and the solid film [54].…”

Section: Printability and Measurable Resistancementioning

confidence: 98%

Surface modification of an ambient UV-cured dielectric to realise electrically conducting traces

Lim

Goh

Liu

et al. 2015

Surface and Coatings Technology

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Citation: LIM, Y.Y. ... et al, 2015. Surface modification of an ambient UVcured dielectric to realise electrically conducting traces. Surface and Coatings Technology, 266, Additional Information:• This article was accepted for publication in the journal, Surface and Coat- AbstractThere has been much interest in the printing of silver inks onto flexible substrates, for which intermediate dielectric layers are often required to achieve suitable wettability. This work seeks to realize continuous silver traces overprinted onto UV-curable dielectrics through surface modification techniques (thermal and UV-ozone post treatments), when the UV light source used for the curing is non-optimal. Two UV curable dielectric materials were deposited and the effects of curing time and curing atmosphere on the inkjet printability of a commercially available silver ink were investigated. Good wettability of the silver ink was obtained following ozone treatment of the dielectric layers, where the treatment required was found to be a function of the dielectric formulation and the curing atmosphere. Water droplet contact angle measurements were used to analyse the resulting changes in the surface conditions of the dielectric layers. The results provided an indication, but were not sufficient for predicting whether silver traces with measurable resistance could be subsequently obtained. Instead, measurable silver trace resistances were found to be influenced by the occurrence of cracks in the trace and possibly the degree of cross-linking present in the dielectric. Following these results, the authors demonstrate that electrically conductive traces can be achieved on ambient cured samples, which yields a more flexible solution compared to inert cured samples.

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Solidification and Ordering during Directional Drying of a Colloidal Dispersion

Cited by 94 publications

References 28 publications

Drying Dip-Coated Colloidal Films

Drying Dip-Coated Colloidal Films

Autostratification in Drying Colloidal Dispersions: Experimental Investigations

Surface modification of an ambient UV-cured dielectric to realise electrically conducting traces

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