Numerical simulation of complex fluid drying in a Hele-Shaw cell

Hsueh, Ching; Doumenc, F.; Guerrier, B.

doi:10.1140/epjst/e2013-01780-8

Cited by 5 publications

(3 citation statements)

References 7 publications

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“…The rationale is detailed below. According to previous studies, strong extensional flow exists at the top surface due to increasing solvent evaporation rate moving toward the contact line. , Going from the free surface toward the bottom substrate, the flow type transitions from extension dominant to shear dominant, bound by the nonslip boundary condition at the bottom interface in contrast to the zero shear boundary condition at the free surface (Figure a). , This flow type transition can result in distinct anisotropic particle alignment in the two different zones. For instance, Trebbin and co-workers observed, in a flow passing through an expanding channel, different orientation of fibrillary micelles in a shear dominant zone near the channel wall compared to an extension dominant zone at the channel center .…”

Section: Discussionmentioning

confidence: 68%

“…According to previous studies, strong extensional flow exists at the top surface due to increasing solvent evaporation rate moving toward the contact line. 45,46 Going from the free surface toward the bottom substrate, the flow type transitions from extension dominant to shear dominant, bound by the nonslip boundary condition at the bottom interface in contrast to the zero shear boundary condition at the free surface (Figure 6a). 47,48 This flow type transition can result in distinct anisotropic particle alignment in the two different zones.…”

Section: ■ Discussionmentioning

confidence: 99%

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Understanding Interfacial Alignment in Solution Coated Conjugated Polymer Thin Films

Zhao

Newbloom

et al. 2017

ACS Appl. Mater. Interfaces

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Domain alignment in conjugated polymer thin films can significantly enhance charge carrier mobility. However, the alignment mechanism during meniscus-guided solution coating remains unclear. Furthermore, interfacial alignment has been rarely studied despite its direct relevance and critical importance to charge transport. In this study, we uncover a significantly higher degree of alignment at the top interface of solution coated thin films, using a donor-acceptor conjugated polymer, poly(diketopyrrolopyrrole-co-thiophene-co-thieno[3,2-b]thiophene-co-thiophene) (DPP2T-TT), as the model system. At the molecular level, we observe in-plane π-π stacking anisotropy of up to 4.8 near the top interface with the polymer backbone aligned parallel to the coating direction. The bulk of the film is only weakly aligned with the backbone oriented transverse to coating. At the mesoscale, we observe a well-defined fibril-like morphology at the top interface with the fibril long axis pointing toward the coating direction. Significantly smaller fibrils with poor orientational order are found on the bottom interface, weakly aligned orthogonal to the fibrils on the top interface. The high degree of alignment at the top interface leads to a charge transport anisotropy of up to 5.4 compared to an anisotropy close to 1 on the bottom interface. We attribute the formation of distinct interfacial morphology to the skin-layer formation associated with high Peclet number, which promotes crystallization on the top interface while suppressing it in the bulk. We further infer that the interfacial fibril alignment is driven by the extensional flow on the top interface arisen from increasing solvent evaporation rate closer to the meniscus front.

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Section: Discussionmentioning

confidence: 68%

Section: ■ Discussionmentioning

confidence: 99%

Understanding Interfacial Alignment in Solution Coated Conjugated Polymer Thin Films

Zhao

Newbloom

et al. 2017

ACS Appl. Mater. Interfaces

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“…During ADDC, the fluid flows involve capillary flow induced by non-uniform solvent evaporation, Marangoni flow caused by a surface tension gradient, and Couette flow driven by substrate movement. 29,36,37 A fundamental feature is the presence of a stagnation point, where the streamline is perpendicular to the solution surface, separating the fluid into the ''upward flow region'' and ''recirculation flow region'' (Fig. 3a).…”

Section: Fluid Flow Simulationmentioning

confidence: 99%

Key role of the meniscus shape in crystallization of organic semiconductors during meniscus-guided coating

et al. 2020

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Optimized Charge Transport in Molecular Semiconductors by Control of Fluid Dynamics and Crystallization in Meniscus‐Guided Coating

Yildiz

Wang

Borkowski

et al. 2021

Adv Funct Materials

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The effects of the casting speed and solute concentration on the crystallization of 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT) during meniscus-guided coating (MGC) are investigated, and three morphological subregimes with increasing casting speed are identified: I) an isotropic domain-like structure; II) unidirectionally aligned crystalline bands; and III) a corrugated dendritic morphology. Interestingly, increasing the solute concentration does not affect these morphologies but merely the associated transition velocities. Numerical simulation of both the fluid dynamics in the coating bead and the crystallization itself not only explains these morphological trends but also the decrease in the width of the crystalline bands of morphology II with the casting speed. They demonstrate that the latter provides an optimal processing window for organic field-effect transistors, with minimized charge trapping, maximized on/off ratio, and reliability factor.

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Numerical simulation of complex fluid drying in a Hele-Shaw cell

Cited by 5 publications

References 7 publications

Understanding Interfacial Alignment in Solution Coated Conjugated Polymer Thin Films

Understanding Interfacial Alignment in Solution Coated Conjugated Polymer Thin Films

Key role of the meniscus shape in crystallization of organic semiconductors during meniscus-guided coating

Optimized Charge Transport in Molecular Semiconductors by Control of Fluid Dynamics and Crystallization in Meniscus‐Guided Coating

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