Radiative Striations of Spin-Coating Films: Surface Roughness Measurement and in-situ Observation

Kozuka, Hiromitsu; Ishikawa, Yuta; Ashibe, Naoki

doi:10.1023/b:jsst.0000047996.53649.3d

Cited by 21 publications

(26 citation statements)

References 4 publications

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“…Sol-gel coating processes are widely used for preparing inorganic and organic-inorganic hybrid films, where micrometersized patterns such as unevenness in thickness or ridges are formed on the surface of the films under certain conditions. [22][23][24][25][26][27][28][29][30][31] We previously prepared sol-gel-derived silica and titania dipcoating films at extremely low substrate withdrawal speeds below 1.0 cm min À1 , and found the spontaneous formation of stripe patterns based on the ''coffee-ring effect'' during the dipcoating. 29 The stripe patterns were arranged perpendicular to the withdrawal direction, and the height and width increased with decreasing withdrawal speeds.…”

Section: Introductionmentioning

confidence: 99%

Spontaneous pattern formation based on the coffee-ring effect for organic–inorganic hybrid films prepared by dip-coating: effects of temperature during deposition

2012

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We prepared silica-poly(vinylpyrrolidone) (PVP) hybrid films via a temperature-controlled dip-coating process and investigated the influence of the coating temperature (i.e., the temperature of substrates, solutions and atmosphere) on the spontaneous pattern formation based on the ''coffee-ring effect''. Micron-scale stripe patterns were spontaneously formed on the surface of the films at high coating temperatures over 40 C during dip-coating. The stripe patterns were arranged perpendicular to the withdrawal direction, and the height and width of the patterns increased with increasing coating temperature. Such spontaneous pattern formation is attributed to the evaporation-driven capillary flow of coating solutions at the meniscus, and the stripe patterns with larger heights and widths are thought to be achieved by the capillary flow activated at higher coating temperatures.

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Section: Introductionmentioning

confidence: 99%

Spontaneous pattern formation based on the coffee-ring effect for organic–inorganic hybrid films prepared by dip-coating: effects of temperature during deposition

2012

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“…A comparative study on the effects of various polymer additives will provide valuable insight into the crack suppression mechanism. Striped patterns (also called striations [17,18]) were noticeable in thick films of d > 100 nm as seen in the right half of the image in Fig. 4.…”

Section: Resultsmentioning

confidence: 99%

Sol-Gel Preparation of Thick TiO<sub>2</sub> Films for Structural Coloration

Yasuda

Kojima

Mori

2018

Trans. Mat. Res. Soc. Japan

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We studied sol-gel processing of thick and crack-free TiO 2 films to synthesize structural color materials. The viscosity of the alkoxide-based precursor sols was stabilized by the addition of acetyl acetone, which improved control of the spin coating thickness. We used a TiO 2 /SiO 2 /TiO 2 triple-layer structure and second-order reflection conditions to produce structural coloration. This design yielded a sharp spectral peak and bright coloration; however, a TiO 2 layer with a thickness greater than 200 nm was required, which is much thicker than that required for the first-order of reflection. Crack formation in the thick films was suppressed by the addition of ethyl cellulose to the precursor sols. As a consequence, color-tuned TiO 2 /SiO 2 /TiO 2 films were successfully prepared and exhibited various bright colors in the visible light wavelength range, including two primary colors of light, namely blue and green. Green coloration from flake-shaped particles was also demonstrated.

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“…The other is a log scale sampling, where the time points are evenly spaced on a logarithmic scale as in Eq. (10). The examples of the collocation points are shown in Fig.…”

Section: Density Distribution Of Collocation Pointsmentioning

confidence: 99%

“…Striation is another typical thickness undulation, which appears as radial spoke-like patterns all over the film (see, e.g., [4,5]). The mechanism of striation has been investigated and, Marangoni-Bénard instability is considered to play a fundamental role [4][5][6][7][8][9][10][11][12]. Shiratori et al investigated the formation process of striations by measuring spatio-temporal thickness variations during a spin coating for mixtures of epoxy resin and xylene solvent [13].…”

Section: Introductionmentioning

confidence: 99%

Physics-informed neural network applied to surface-tension-driven liquid film flows

Nakamura,

Shiratori,

Takagi

et al. 2021

Preprint

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A physics-informed neural network (PINN), which has been recently proposed by Raissi et al. [J. Comp. Phys. 378, pp. 686-707 (2019)], is applied to the partial differential equation (PDE) of liquid film flows. The PDE considered is the time evolution of the thickness distribution h(x, t) owing to the Laplace pressure, which involves 4th-order spatial derivative and 4th-order nonlinear term. Even for such a PDE, it is confirmed that the PINN can predict the solutions with sufficient accuracy. Nevertheless, some improvements are needed in training convergence and accuracy of the solutions. The precision of floating-point numbers is a critical issue for the present PDE. When the calculation is executed with a single precision floating-point number, the optimization is terminated due to the loss of significant digits. Calculation of the automatic differentiation (AD) dominates the computational time required for training, and becomes exponentially longer with increasing order of derivatives. By splitting the original 4th-order one-variable PDE into 2nd-order two-variable PDEs, the computational time for each training iteration is greatly reduced. The sampling density of training data also significantly affects training convergence. For the problem considered in this study, improved convergence was obtained by allowing the sampling density of training data to be greater in earlier time ranges, where the rapid diffusion of the thickness occurs.

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Radiative Striations of Spin-Coating Films: Surface Roughness Measurement and in-situ Observation

Cited by 21 publications

References 4 publications

Spontaneous pattern formation based on the coffee-ring effect for organic–inorganic hybrid films prepared by dip-coating: effects of temperature during deposition

Spontaneous pattern formation based on the coffee-ring effect for organic–inorganic hybrid films prepared by dip-coating: effects of temperature during deposition

Sol-Gel Preparation of Thick TiO<sub>2</sub> Films for Structural Coloration

Physics-informed neural network applied to surface-tension-driven liquid film flows

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