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The purpose of this paper is to carry out a comprehensive experimental investigation into the role of screen and conductive carbon material formulation on line conductivity and printing capability in the screen printing process, to provide design knowledge and further understanding of the screen printing for printed carbon.

A full factorial experiment was carried out where six carbon materials were printed through ten screens to a polyester substrate under a set of standard conditions.

Material characterization showed that viscosity and the corresponding viscous and elastic material modulli increased with solids content and that the elastic properties at low shear are significant. The solids carbon content materials were unable to produce the minimum printable line features possible with the low carbon materials. Increasing the solids contents reduced the final cured line resistance, reduced the printed line width, increased the film thickness, increased the cross sectional area and reduced the material resistivity. Material resistivities were around 700 to 950 μΩcm were obtained in the printed lines.

Lower material resistivities were obtained with higher solids materials and it is postulated that the increased visco‐elastic nature of the solids content materials, play a role in determining the microscopic structure of the cured film through alignment of the carbon graphite platelets.

A dataset which allows material, screen and print characteristics has been created allowing process optimization and formulation development to be accelerated.

The work provides insight into the role of material properties and process settings on the electrical and physical characteristics of printed carbon.

The study focuses on the development of a numerical model to explore the impact of surface roughness in soft rolling nip contacts, including representation of a real surface. The solution of the governing equations required the application of a multigridding technique to capture the details of the fluid flow within the roughness wavelengths and a minimum number of fluid nodes per wavelength were established. In the case studies, two extreme roughness profiles were considered, longitudinal and circumferential. The longitudinal roughness had a significant impact on nip pressures and pumping capacity, the latter being determined by the minimum film thickness in the nip. The circumferential roughness was found to have a localised effect on film pressure, but only a very small impact on the film thickness profile. The consequent effect on pumping capacity was small.

The paper focuses on the solution of a numerical model to explore the sliding and non‐Newtonian fluid behaviour in soft elastohydrodynamic nip contacts. The solution required the coupling of the fluid and elastomer regimes, with the non‐Newtonian fluid properties being described using a power law relationship. The analysis showed that the fluid characteristics as defined by the power law relationship led to large differences in the film thickness and flow rate with a movement of the peak pressure within the nip contact. The viscosity coefficient, power law index and sliding ratio were shown to affect the nip performance in a non‐linear manner in terms of flow rate and film thickness. This was found to be controlled principally by the level of viscosity defined by the power law equation. The use of a speed differential to control nip pumping capacity was also explored and this was found to be most sensitive at lower entrainment speeds.

Printed flexible circuits that combined conventional silicon technology will enable the realisation of many value added products such as smart packaging for the fast moving consumer goods (FMCG) industry. This paper aims to describe an investigation into integrating silicon and printable circuits for the FMCG packaging industry and this would allow products with features such as brand protection, time temperature indicators, customer feedback and visual product enhancement. Responding to interest from the FMCG packaging industry, an investigation was carried out which investigated the printing conductive silver ink on common packaging substrates.

Standard IC mounting patterns were screen printed using two conductive silver materials (one high silver content traditional paste and one lower silver content gel polymer) to four plastic and three paper substrates which represent common FMCG substrates (HDPE, BOPP, PET and three paper substrates). Materials were characterised in terms of material rheology whereas prints were characterised through electrical performance and printed film topology.

There was a significant interaction between the substrate, silver ink formulation and the resultant line quality, line topology and conductivity. On paper substrates, the absorption of binder into the substrate resulted in denser silver packing and higher conductivity for the paste material. Higher conductivities were obtained on the substrates capable of withstanding higher curing temperatures. On the polymer substrates higher conductivity could be obtained by lower content silver materials due to the denser particle packing in the cured ink film as a result of its higher solvent/lower solids components.

Further work should examine the interactions for other printing processes commonly used in the FMCG industry such as rotogravure of flexography and should also examine nano particle materials. Further work should also address the mechanical adhesion of silicon logic on the substrates and bottlenecks in processing.

The lower silver content gel material potentially provides material cost reduction by a factor of between 4 and 7 for the same conductivity. The gel material also has potential for more uniform performance across all substrate types. Typically 3.1 Ω/cm resistance values are achieved on all substrates for 300 micron lines.

For those in the field of smart packaging the work has highlighted the interaction between silver materials and non PET/PEN substrates in flexible printed circuits. It has demonstrated the implications of rheology, substrate absorbency and materials processing temperature on circuit design. For those seeking printing process understanding it has provided further validation to support material transfer mechanisms in the screen printing process.

The influences of viscous shear stresses on the squeezing film behaviors in porous journal bearings with infinite length are analyzed. Based on the Brinkman model, two general coupled Reynolds‐type equations derived between two curved surfaces are applied to evaluate the bearing characteristics. According to the results obtained, the Brinkman model predicts quite different squeezing film performances to those obtained by using the slip‐flow model and the Darcy model. In addition, the quantitative effects of viscous shear stresses of the Brinkman model upon the porous squeezing film characteristics are more pronounced for porous journal bearings with moderate permeability parameters and higher eccentricity ratios.

A Lagrangian finite element algorithm is described for solving two‐dimensional, time‐dependent free surface fluid flows such as those that occur in industrial printing processes. The algorithm is applied using a problem specific structured meshing strategy, implemented with periodic remeshing to control element distortion. The method is benchmarked on the problem of a stretching filament of viscous liquid, which clearly demonstrates the applicability of the approach to flows involving substantial free surface deformation. The model printing problem of the transfer of Newtonian liquid from an upturned trapezoidal trench (3‐D cavity with a large transverse aspect ratio) to a horizontal substrate, which is pulled perpendicularly downwards from the cavity, is solved computationally using the Lagrangian scheme. The idealized 2‐D liquid motion is tracked from start‐up to the point where a thin sheet forms – connecting the liquid remaining in the cavity to a “sessile” drop on the moving substrate. The effect of varying substrate separation speed is briefly discussed and predictions are made for approximate drop volumes and “limiting” domain lengths.

The purpose of this paper is to optimize the key parameters (mesh count, paper type and ink type) in screen printing, which are affecting the printed ink volume. The objective of the optimization was to maximize the color reliability by decreasing the color difference (ΔE value) of the prints while minimizing the ink consumption. Screen printing is still dominating the printing industry to make cost-effective production when high volumes are needed.

The experiment was designed using the Taguchi method, and the samples were prepared with screen-printing by using the standard squeegee angle and pressure. The effect of mesh count, ink type and paper type on ink consumption was evaluated with using analysis of variances and main effects plots of S/N ratio and standard deviation.

The factors ink type, paper type and mesh count were found significant for ink consumption due to their Probability (P) values which were lower than 0.05. It was determined that the mesh count was the most critical variable with the analysis of variance. The analysis showed that the selection of an optimum mesh count was the key to controlling the amount of the deposited ink. Although mesh counts were inversely proportional with the ink consumptions, they did not affect the color differences as expected.

The optimization of process parameters, that are most effective on the print quality, is necessary to minimize the ink usage and lower the costs and environmental impact without exceeding the desired ΔE value limits.

The resistivity of cured conductive ink films are dependent on a wide range of process parameters. An early indication of the resistivity that is likely to result following curing can enable these parameters to be optimised and, therefore, improve product quality. This paper aims to report on the use of alternating current (AC) impedance measurement techniques on curing printed ink films as a means of assessing the resistivity likely to be attained following the curing process.

Impedance measurements (100 Hz-10 MHz) were performed on curing conductive carbon ink films printed on polyethylene terephthalate substrates during convective heat curing. A jig was designed to incorporate the test structure in an convection oven such that the effect of cure on the structure impedance could be investigated.

The initial impedance was found to decrease with an increase in the measurement frequency. As the ink films were cured, the impedance magnitude across the 100 Hz-10 MHz range converged with the direct current (DC) resistance value. For a given ink, the ratio of initial AC impedance at 10 MHz to final cured resistance was found to be consistent, thus giving a method where final conductivity can be estimated before cure.

Data from printed ink resistance measurements are required to ensure the optimal conductivity of printed devices. However, after the printed structures are fabricated and cured, it is too late to optimise process parameters, leading to significant wastage. AC impedance measurement can give an indication of the final cured resistivity whilst the structure is freshly printed and still in its curing phase, enabling the printing process parameters to be adjusted to improve the resistivity of subsequently printed devices. Measuring AC impedance of printed ink structures in a production environment can, therefore, improve output.

The purpose of this paper is to present a parametric study of the effects of permeability and surface roughness on the hydrodynamic force and the leakage flow rate in an oscillating squeeze film between a rigid surface and a rubber surface.

The study is conducted numerically using a squeeze film model that incorporates the effects of viscoelasticity, permeability and surface roughness.

It is seen that with increasing permeability of the porous rubber block, both the hydrodynamic force and the leakage flow rate decrease. Increasing center line average (CLA) of surface roughness height distribution decreases the leakage flow rate slightly but increases the hydrodynamic force. The decrease in the hydrodynamic force due to using permeable material in squeeze film may be compensated for by deliberately increasing the surface roughness. The effect of variation in frequency of system vibration may be minimized by using optimally selected permeable materials with rough surface.

The paper reports the extension of previous work of the authors and the results of this portion were never published. The findings of this paper are based on original work and have practical value.

There are very few individuals who have studied the question of weights and measures who do not most strongly favour the decimal system. The disadvantages of the weights and measures at present in use in the United Kingdom are indeed manifold. At the very commencement of life the schoolboy is expected to commit to memory the conglomerate mass of facts and figures which he usually refers to as “Tables,” and in this way the greater part of twelve months is absorbed. And when he has so learned them, what is the result? Immediately he leaves school he forgets the whole of them, unless he happens to enter a business‐house in which some of them are still in use; and it ought to be plain that the case would be very different were all our weights and measures divided or multiplied decimally. Instead of wasting twelve months, the pupil would almost be taught to understand the decimal system in two or three lessons, and so simple is the explanation that he would never be likely to forget it. There is perhaps no more interesting, ingenious and useful example of the decimal system than that in use in France. There the standard of length is the metre, the standard of capacity the cubic decimetre or the litre, while one cubic centimetre of distilled water weighs exactly one gramme, the standard of weight. Thus the measures of length, capacity and weight are most closely and usefully related. In the present English system there is absolutely no relationship between these weights and measures. Frequently a weight or measure bearing the same name has a different value for different bodies. Take, for instance, the stone; for dead meat its value is 8 pounds, for live meat 14 pounds; and other instances will occur to anyone who happens to remember his “Tables.” How much simpler for the business man to reckon in multiples of ten for everything than in the present confusing jumble. Mental arithmetic in matters of buying and selling would become much easier, undoubtedly more accurate, and the possibility of petty fraud be far more remote, because even the most dense could rapidly calculate by using the decimal system.