转移涂布，剪切速率

… shear rate somehow regulates or controls coating flows (and its corollary that coating flows take place at certain characteristic shear rates … a given shear stress, the observed shear rate …

Polymer conductors that are solution-processable provide an opportunity to realize low-cost organic electronics. However, coating sequential layers can be hindered by poor surface wetting or dissolution of underlying layers. This has led to the use of transfer printing where solid film inks are transferred from a donor substrate to partially fabricated devices using a stamp. This approach typically requires favorable adhesion differences between the stamp, ink, and receiving substrate. Here, we present a shear-assisted organic printing (SHARP) technique that employs a shear load on a post-less polydimethylsiloxane (PDMS) elastomer stamp to print large-area polymer films that can overcome large unfavorable adhesion differences between the stamp and receiving substrate. We explore the limits of this process by transfer printing poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) films with varied formulation that tune the adhesive fracture energy. Using this platform, we show that the SHARP process is able to overcome a 10-fold unfavorable adhesion differential without the use of a patterned PDMS stamp, enabling large-area printing. The SHARP approach is then used to print PEDOT:PSS films in the fabrication of high-performance semitransparent organic solar cells.

… wet films made by SPBP, blade coating and spin coating are visualized by high speed … coating is irregular and random. The simplified flow model of SPBP suggests that the shear rate …

… arrangement of coatings was determined for coatings made … explained by variation of shear rate, which was controlled by … in a higher transfer rate and overall higher coating thickness …

… the impact of shear-thickening on the liquid transfer from an … shear and extensional thickening as verified by steady shear and … The amount liquid transfer from the cavity was studied with …

… when the shear rate crosses a threshold value. In other words, under the increasing shear rate, … in the weight fraction of solid component, the transfer of force by the agglomerates in the …

Coat-hanger die design aims for optimization of the die geometry of the body and the flow distribution manifold, such that through the exit at the die lip homogeneous distribution of the polymer melt is achieved. This paper proposes a novel methodology for deriving the design equations of the coat-hanger die geometry for some specific extrusion materials and provides fluid–solid interaction simulations for validations. The basis for the calculations is the Casson rheological model, analytic velocity profiles for the pseudoplastic flow through circular pipe and slit, and the constant shear rate coat-hanger die design methodology developed by Winter and Fritz. The geometry obtained was then evaluated using the fluid-structure interaction numerical simulation approach. The sensitivity of the outlet velocity uniformity and die body deformation due to the material and mass flow rate change were investigated using the finite element software, Ansys. It was found that the homogeneity of the outlet velocity is very sensitive to the extrusion materials. The structural analysis of the solid die body also resulted in higher deformations when using some other extrusion materials different from the initial design. Mass flow rate increase only resulted in large zones of stagnation, which occurred around the melt as it passes from the manifold to the slit region. Therefore, it is recommended to define the required range of mass flow rate to prevent the formation of stagnation zones.

… Because shear effects can be neglected when using rolls rotating at the same speed in forward mode, we propose to redefine the capillary number using the extensional viscosity (η E ) …

… -Newtonian shear behavior reduces the pressure distribution, and increases the coating … in polymer solutions makes only a minor contribution to the roll-separating (load-carrying) force. …

… Given the rather modest state-of-the-art of coating rheology … but limits itselfto reviewing basic rheological concepts and then … in rheological measurements, namely steady shear, transient …

… to the rheological properties of the coating fluids. … shear rate; at a shear rate of 7500s 1, no overshoot was observed. They concluded that in the roll coating process, where the shear …

… Within the nip between rotating rolls, the paint experiences high … rolls, and this occurs at low shear rates. Transientand steady-state rheological measurementsare performed using shear …

… st be~bre the start of le~oiling (fixed at t 0), the palnt fic~.,ving betw<-en the coater rolls is subjetted to high shear, whiN~ c~nK.~..~tel} ....... .,~,~+ c,,...y,' its stN~,c ture. Then for t>0, …

… 3-roll full roll coating is based on the reverse roll coating mode between the pick-up and metering rolls. … of considerable shear force to effectively align metallic flakes in roll coating flows. …

… present rheological data on four coating colors with substantially different runnability. Apart from the high shear viscosity, viscoelasticity as well as apparent wall slip effects at high shear …

… of describing the fluid-film rheology in appropriate detail (shear-thinning, tension-thinning/thickening, elasticity). The findings of this research are applicable across a wide range of …

In this study an incompressible flow with non-Newtonian fluids in the reverse roll coating process was investigated. Non-Newtonian behavior of the coating fluid was accounted by using power law model with power index, n, ranging from 0.8 to 1.2. Effect of roll speed ratio (V2/V1) of the panel roll to the applicator roll and gap distance on the coating film thickness were also investigated. Numerical results were in good agreement with those of experimental data within 15%-20%. Results indicated that the film thickness ratios are function of power-law index, roll speed ration and ratio of roll radius to gap distance. The equations for film thickness ratio were obtained from numerical results as shown below: t2 t1 =0.89n ( V2 V1 −0.83 H0 Rm 0.0025 , t3 t1 =65.6n ( V2 V1 −0.043 H0 Rm 0.624 , where t1, t2 and t3 are inlet film, transferred film and leakage film thickness, respectively, n is power-law index, V1 and V2 are roll speed of applicator roll and panel roll, Rm is average radius of two rolls and H0 is gap distance. The correlations are accurate within 10% for 0.8≤n≤1.2, 0.5≤V2/V1 ≤2, and 7.7×10 ≤H0/Rm ≤1.54×10 −4. AMS subject classifications: 76A05

… The essence of reverse roll coating is the rapid high-shear flow … Non·Newtonian rheological behavior can stronlly afect both … the viscosity at the appropriate shear rate. Experiments with …

… coating bead. The thin metered film remaining on the applicator roll is subsequently transferred to the web (the substrate to be coated)… The initial film application and the final film transfer …

The blade coating is an essential industrial technique that involves applying a protective liquid layer to a moving surface with a smoothing blade. In this article we demonstrated the non‐isothermal analysis of blade coating using viscoelastic fluid model numerically. The flow equations are made simplify using lubrication approximation theory (LAT). The resulting dimensionless flow and energy equations are simulated using a robust fourth‐order Runge–Kutta and Newton–Raphson methods to calculate the coating thickness (), stream function, velocity pressure, temperature profile, pressure gradient and blade load. The impact of the slip and involved parameters on these quantities are deliberated through various graphs and tables. The temperature distribution increases as the Brinkman number rises, with the maximum temperature occurring in the nip region of the flow. The mechanical quantities such as coating thickness increases while the blade load decreases with increasing the values of the slip parameter as compared with Newtonian model for both plane and exponential coater. The temperature distribution increases as the Brinkman number increases. The coating thickness increases as the slip parameter value increases, while the blade load decreases. The pressure profile shows an increasing trend with increasing the values of the blade height ratio (K). The pressure profile increases with increasing the values of α1 while its shows decreasing trend with increases the value of the α2.

▪ Abstract Coating is the process of applying thin liquid layers to a substrate, often a moving web. Complex coating processes can be approached through examination of their fluid mechanical components. The flow elements reviewed in this article include the boundary layer along a moving wall, the dynamic wetting line, withdrawal from a pool, flow metered by a narrow channel, die flow, flow on an incline, the freely falling liquid curtain, premetered coating with a small gap, and flow after coating. Although some flow elements are well studied and understood, others require additional investigation. Genuinely predictive modeling of complex coating processes is not yet possible and coating practice remains largely empirical. Nonetheless, coating science is sufficiently advanced that physical insights and mathematical models greatly benefit design and practice.

… coated, is quite different. A relatively simple prototype flow incorporating a dynamic wetting line is fluid … that flows down an inclined plane for transfer to a moving web. Various designs of …

… and to avoid roll damage, a deformable cover on the transfer roll is … coating by means of computer fluid dynamic simulations of the metering nip flow. Newtonian fluids and paper coating …

… limited to Newtonian fluids. In this study, new computational fluid dynamics (CFD) and analytical models to study the penetration of fluid into porous media during slot die coating were …

The steady‐state laminar nonisothermal, incompressible viscoelastic fluid flows with the Jeffrey model between two counterrotating (same direction) rolls are studied analytically. The Jeffrey model is reduced to the Newtonian model after some appropriate modifications. The new dimensionless governing equations are acquired through suitable nondimensional values. The lubrication approximation theory is employed for the simplification of emerging equations. The exact expressions for pressure gradient, velocity, temperature, and flow rate are accomplished whereas some quantities of interest such as pressure, coating thickness, power transmitted by rolls to the fluid, and roll separation force are computed numerically by using a numerical method. The influence of emerging parameters such as the ratio of relaxation time to the retardation time λ 1 ${\lambda }_{1}$ , magnetohydrodynamic (MHD) parameter M $M$ and Brinkman number B r $Br$ on velocity profile, temperature profile, pressure gradient, pressure distribution, coating thickness, power input, and force of roll separation are presented numerically in a tabular way and specific outcomes are demonstrated graphically. The MHD acts as a regulatory parameter for various quantities of important interest, such as velocity, coating thickness, and temperature. It is worth noting that the coating thickness decreases as modified capillaries number is increased.

… The action of viscous lifting results in fluid entering the conjunction … A coating “bead” is formed and fluid exits downstream of the nip as two films – one which returns to the coating pan, …

The drivers in the development of large area micro-and nanostructuring roll-to-roll (R2R) methods have been hologram security stickers, flexible electronics, graphene electrodes

… Roll-to-roll (R2R) coating technologies, with their advantages in terms of high … dip coating, knife-over-edge coating, slot-die coating, direct- and micro-gravure coating, and spray coating. …

The shear-rolling process is a promising directed self-assembly method that can produce high-quality sub−10 nm block copolymer line-space patterns cost-effectively and straightforwardly over a large area. This study presents a high temperature (280 °C) and rapid (~0.1 s) shear-rolling process that can achieve a high degree of orientation in a single process while effectively preventing film delamination, that can be applied to large-area continuous processes. By minimizing adhesion, normal forces, and ultimate shear strain of the polydimethylsiloxane pad, shearing was successfully performed without peeling up to 280 °C at which the chain mobility significantly increases. This method can be utilized for various high-χ block copolymers and surface neutralization processes. It enables the creation of block copolymer patterns with a half-pitch as small as 8 nm in a unidirectional way. Moreover, the 0.1-second rapid shear-rolling was successfully performed on long, 3-inch width polyimide flexible films to validate its potential for the roll-to-roll process.

… coating thickness is inversely proportional to the line speed. To the best of our knowledge, continuous, roll-to-roll coating of … Shear flow measurements were performed with a shear rate …

… roll-to-roll reverse gravure process for controlled anisotropy in PVA/CNC nanocomposite coatings … The setting of shear rate measurement for different coating formulations can be found …

The integration of platelet-shaped montmorillonite particles to improve the oxygen barrier of polyvinyl-alcohol-based barrier layers is state-of-the-art, but research on roll-to-roll coatings of such composite barrier lacquers has not been widely published. In this study, two different coating techniques, slot-die and reverse gravure, were used on a roll-to-roll scale to apply barrier lacquers comprising polyvinyl alcohol and montmorillonite. The lacquers were analyzed regarding viscosity at certain shear rates and surface energy and the dried coating layers regarding oxygen barrier, surface morphology, and particle orientation. Low permeability coefficients delivering a high oxygen barrier of 0.14 and 0.12 cm3 (STP) 1 μmm2 d bar were achieved for the coating layers with slot-die and reverse gravure coating, respectively. It turned out that the properties of the barrier lacquer need to be adjusted to the coating technique to achieve high oxygen barrier performance. By tailoring the barrier lacquer formulation, the orientation of the platelet-shaped montmorillonite particles can be achieved using both techniques. A low solid content of down to 3 wt% is preferable for the premetered slot-die coating, because it results in low agglomeration quantity in the coating layer. A high solid content of up to 9 wt% is preferable for the self-metered reverse gravure coating to assure a homogeneously coated layer.

Here, we report a printing mechanism that utilizes mechanical stress for dry transfer of chemically reduced graphene oxide (r-GO) thin film. We discover that shear stress induced on the elastomeric stamp surface facilitates delamination of the deposited r-GO thin film from the stamp. Shear stress is introduced in a roll-to-roll printing system by rotating the stamp roller faster than the substrate roller. Energy-balance theory for thin film transfer is suggested to analyze the film delamination behavior with induced shear stress. Facile dry transfer of r-GO thin film onto flexible substrates is demonstrated in a roll-to-roll printing system at a printing rate of 5 mm/min with calculated shear stress of 325.43 kPa.

A simple, scalable, non-lithographic, technique for fabricating durable superhydrophobic (SH) surfaces, based on the fingering instabilities associated with non-Newtonian flow and shear tearing, has been developed. The high viscosity of the nanotube/elastomer paste has been exploited for the fabrication. The fabricated SH surfaces had the appearance of bristled shark skin and were robust with respect to mechanical forces. While flow instability is regarded as adverse to roll-coating processes for fabricating uniform films, we especially use the effect to create the SH surface. Along with their durability and self-cleaning capabilities, we have demonstrated drag reduction effects of the fabricated films through dynamic flow measurements.

… of roll-to-roll manufacturing of PSC (eg, references 4–10) with a record efficiency of 3.5%,8 developing a stable process for large area coating … values for concentration, shear rate, and …

… The following chapter is a nonexhaustive review of roll-to-roll deposition techniques that are of interest for high-throughput, cheap preparation of flexible electronics. The chapter will …

… Roll-to-roll technical parameters. The effects of changing shear rate and coating speed on the … In this work, the transmittance is controlled by coating speed for film thickness (Figure 3b). …

The interplay between non-Newtonian effects, gravity, and substrate topography is examined in this theoretical study for the transient two-dimensional flow of a thin non-Newtonian film. The study is a continuation of the previous work by Khayat and Welke [Phys. Fluids 13, 355 (2001)], which focused on the influence of inertia on a Newtonian film. The fluid emerges from a channel and is driven by a pressure gradient maintained inside the channel. The substrate is assumed to be stationary and of arbitrary shape. The flow is dictated by the thin-film equations of the “boundary layer” type, which are solved by expanding the flow field in terms of orthonormal modes in the transverse direction and using the Galerkin projection, combined with a time-stepping implicit scheme, and integration along the flow direction. Gravity and substrate topography can have a significant effect on transient behavior, but this effect varies significantly, depending on whether the fluid is Newtonian, shear thinning or shear thickening. Wave formation and propagation, as well as steady film flow are examined. It is found that shear-thickening fluids tend to accumulate near the channel exit, exhibiting a standing wave that grows with time. This behavior clearly illustrates the difficulty faced with coating shear-thickening fluids at any level of inertia. The influence of the substrate topography has been explored in the case of undulated substrate.

… fluids, one which is weakly viscoelastic but exhibits a strongly shear-thinning viscosity, and another fluid with strong viscoelastic characteristics, are presented in Sect. 4. Using the …

… centrifugal forces cannot deform or shear it. Thus,the … shear rates and show no spikes at the origin. The power-law model of non-Newtonian fluids in a free surface axisymmetric shear …

… the same non-Newtonian behavior at high shear rates. As a … for modeling the nonNewtonian flow was an extension of the … With the non-Newtonian flows of this paper the fourth-order …

… where Q is the flow rate of the coating sample and ∆P is the pressure drop … non-Newtonian fluids; the shear stress-dependent viscosity of these materials can lead to nonparabolic flow in …

Abstract The functionality of several coated products, such as anti-reflection films and flexible electronics, depends on the complex microstructure of the deposited liquid layer. In many of these applications, the coating liquid is a particle suspension composed by small, solid particles suspended in a viscous liquid medium. Particle suspensions are classified as non-Newtonian fluids, especially at high concentrations. The non-Newtonian behavior of the coating liquid strongly affects the inner structure of the deposited liquid layer and the operability limits of slot coating processes. In this work, we study particle migration and the low-flow limit in slot coating flows of particle suspensions. Both shear rate sensitive and non shear rate sensitive suspensions are considered, and shear-induced particle migration is described by the Diffusive Flux Model. The conservation equations are solved together with the elliptic mesh-generation method to compute the position of the free surfaces using a stabilized Finite Element Method. The results show how particle migration and the rheology of the coating liquid affect the final particle distribution on the deposited liquid film and the process limits in a typical slot coating flow.

… increases with increasing power law index n, whereas the limit of coating speed decreases due to a shear thickening effect. We can understand the reason for the high limit of …

Roll coating (RC) is a fundamental process in both industrial and decorative applications, including the production of wallpapers, plastic and photographic films, adhesive tapes, magnetic recording media, and packaging materials. In this study, we develop a mathematical model for the flow of Powell–Eyring fluid confined within a narrow gap formed between a moving roll and a fixed substrate. An analytical framework based on the perturbation method is constructed to obtain approximate solutions for the velocity field, temperature distribution, pressure gradient, and pressure profile. A comprehensive comparison between numerical and analytical results is presented, validating the accuracy and reliability of the proposed formulations. Parametric analysis highlights the impact of key material and flow properties on coating thickness, velocity, pressure distribution, temperature variation, separation force, power input, and Nusselt number. The maximum coating thickness attains 0.7233 at W e = 0.9 , while the minimum value is 0.5810 at F = 0.09 . Nusselt number increases with higher Brinkman number, signifying stronger heat transfer effects. A mechanism for controlling the coating thickness, power input, separation force, Nusselt number, and pressure distribution is provided by the material properties involved, offering practical insights for optimizing RC operations across diverse industrial applications.

… to assure the uniform coating flow distribution of various non-Newtonian shear-thinning liquids at the die exit in a slot coating system. Flow patterns of non-Newtonian liquids inside the …

… We are concerned here with the coating thickness and the question of how sensitive the … viscous effects by incorporating a simple shear dependent viscosity function into the analysis. …

Multilayer sol-gel optical high reflectors with greater than 99% reflection have been prepared on substrates up to 20 cm in diameter by spin coating silica/alumina colloidal suspensions. These coatings are radially nonuniform, owing to the extensive shear-thinning rheology of the high-index alumina suspension. To a large degree the film thickness nonuniformity can be compensated for by the reflection bandwidth. The rheological properties of the alumina suspension under steady shear have been measured. The low-shear reduced viscosity and the shear-thinning time constant are shown to vary exponentially with φ2, where φ is the solids volume fraction. At φ=0.1 the sol has effectively gelled. A model for spincoating with a non-Newtonian fluid has been developed that uses the Carreau rheology model to fit the measured viscometric data. Modeling and experimental results show that as long as these non-Newtonian effects are sufficiently large (as in this case) the radial film uniformity is determined only by these parameters and cannot be significantly influenced by spin rate, initial solids fraction, or any other parameters under the control of the operator. However, most of the film thickness variation occurs in the first 1–2 cm from the substrate center, leaving the remainder almost uniform. Therefore the degree of nonuniformity does not appreciably increase with increasing substrate size.

… thickness of wet films. The polymethylphenylsilane homopolymer has shear ratedependent flow … ior and evaporation, both determining the final coating thickness. So, the mathematical …

… , leading to enhanced secondary minima and the potential for shear dependent alignment. We speculate that the shear dependent aggregation of TiO 2 particles into string-like …

In industrial continuous galvanising lines (CGL) impinging gas jets are often employed to remove excess coating material from the steel strip. The majority of the coating fluid dragged up from the molten metallic alloy bath is removed by this process-and returned to the bath-leaving a very thin film of the metallic alloy coating to remain on the strip. As the strip exits upwards out of the bath the drag-out thickness of the coating is of mm-order and after the strip passes through the active region of jet-impingement the coating thickness is reduced to μm-order. Achieving a target average final (i.e. post-jet impingement region) coating thickness requires an appropriate combination of the set of control parameters of the process: the strip speed U, mean velocity of the gas exiting the jet lip gap Uo (i.e. jet plenum pressure) the offset of the jet opening from the strip H, the size of the jet lip gap d and the angle the jet centreline makes with the horizontal θ. These settings Coating Film Profiles Generated by Fluctuating Location of the Wiping Pressure and Shear Stress

… and the development of high-uniformity coating processes. … thickness uniformity of photoresist films fabricated by blade coating. … flow behavior and interfacial mass transfer mechanisms. …

… the coating speed. Interesting is the question about the uniformity of the nominal film thickness, … This chapter shows that the film thickness uniformity in the machine direction is controlled …

Angular color uniformity (ACU) is one of the most important optical parameters of white lighting emitting diodes (LEDs). In this paper, we proposed a kind of phosphor coating method to enhance ACU of phosphor-converted white LEDs with conventional chips by the combination of substrate structure design and phosphor dip-transfer coating. Through this method, compact and optimal phosphor layer arrangements for high ACU can be realized. Optical simulations and experiments were conducted to examine its ACU performance. Compared with conventional phosphor dispensing coating, the present method shows very high ACU performance. Extremely small angular correlated color temperature (CCT) deviations were obtained, which are less than 200K at average CCTs ranging from 4000 K to 6000 K.

This article examines a wire coating technique using a viscoelastic Eyring–Powell fluid in which magnetohydrodynamic (MHD) flow, thermal transfer, and Joule heating effects are studied. Temperature-dependent, variable-viscosity models are used. Flexible-viscosity models which are temperature dependent are also considered. The interface of the thermal boundary layer which describe the flux and thermal convection phenomena, are evaluated by using a dominant numerical technique known as the fourth-order Runge–Kutta method. In particular, this article takes into account the impact of a permeable matrix which behaves like a dielectric in order to avoid heat dissipation. The effect of thermal generation is also explained, since it controls power. The novel effects for the numerous parameters which affect the velocity and temperature profiles on the wire coating process are investigated through graphs explained in detail. These include non-Newtonian, hydromagnetic, permeability, and heat source/sink effects. For validation purposes, the numerical scheme is also compared with a semi-numerical technique HAM and BVPh2 software, and found a closed agreement with the numerical results.

… The viscosities of the coating colors were measured in the low shear-rate region (58-1465 s -… The viscosity of the coating colors at shear rates exceeding 104s -1 was determined using a …

… to measure the viscosity of fluids at high shear rates and, … viscosity of the plastisols is extremely dependent on plasticizer amount, even at the high shear rates typical of the coating …

… coating was re duced by increasing extensional viscosity. … that the extensional viscosity can be used to predict the coating … extension rate which prevails in the specific coating process. …

… rates is relevant in many processes involving coating, spraying… to obtain true shear rates and true viscosities from the … affect the viscous response at high shear rates; centrifugal …

The roll coating method is of considerable significance in several industries, as it is applied practically in the production of paint, the manufacturing of PVC-coated cloth, and the plastic industry. The current study theoretically and computationally analyses the Powell–Eyring fluids with variable viscosity during the non-isothermal roll-over web phenomenon. Based on the lubrication approximation theory (LAT), the problem was formulated. The system of partial differential equations (PDEs) obtained from the mathematical modeling was further simplified to a set of ordinary differential equations (ODEs) using suitable transformations. A regular perturbation method was implemented to obtain the solution in terms of velocity, pressure gradient, pressure, and flow rate per unit width. This study also captures important engineering characteristics such as coating thickness, Nusselt number, shear stress, roll/sheet separating force, and roll-transmitted power to the fluid. Along with a comparison between the present work and published work, both graphical and tabular representations wer made to study the effects of various factors. It was observed that the velocity profile is the decreasing function of non-Newtonian and Reynold viscosity parameters. In addition, the response surface methodology (RSM) was employed to investigate the sensitivity of the shear stress and the Nusselt number.