The impact of solvent characteristics on performance and process stability of printed carbon resistive materials

Carbon conductive pastes deposited by screen printing are used in many commercial applications including sensors, PCB, batteries, and PV, and as such represent an important value-added coating. An experimental investigation was carried out into the role of the solvent on the drying characteristics, conductivity, and process consistency in screen printed carbon pastes. Four materials with solvent boiling points between 166 and 219°C were deposited at film thickness between 6 and 16 μm, and the sheet resistance and film thickness were measured after successive passes through an industrial dryer operating with an air temperature of 155°C. Sheet resistances of 14 Ω/sq. were obtained with the thicker films while thinner films produced a sheet resistance of 46 Ω/sq. Thinner films achieved a stable resistivity within a 2.5-min residence time, while the thicker films required a residence time in excess of 12.5 min to achieve a stable resistivity. As well as prolonging drying times, the higher boiling point increased the resistivity of the cured film. It is postulated that the lower resistance of the faster drying materials is a result of film stressing increasing inter particle contact. Process models indicate that multiple thin layers are a more efficient means of manufacture for the process parameters examined

Modeling of mechanical properties of macroporous hydrogel

The research is supported by the Grant Agency of the Czech Republic by project No GA17-08531S Computational design of hydrogel cell scaffolds.Macroporous hydrogels with controlled morphology are widely used in biomedical fields, as drug delivery, tissue engineering, analytical and technical separations or responsive constructs. Porosity can be achieved by several methods. In the preparation of physical experiments it is made by salt crystals which are extracted from the hydrogel after polymerization. The salt crystals have different sizes and shapes. The pore sizes and their distribution affects the final mechanical properties. Such polymer structure is designed by simulations. The simulated structure is than transfered into ANSYS environment and its mechanical properties are examined and compared with experiments

Modelling of swelling and deformations of homogeneous hydrogel

Grant agency of Czech Republic by project No 17-08531S Computationally designed hydrogel cell supports. Additional support provider is Student Grant Competition by project No SGS19/157/OHK2/3T/12 Modelling, control and design of mechanical system 201

Modeling of the mechanical behavior of polymer hydrogels

The research is supported by Grant Agency of the Czech Republic by project No 17-08531S Computationally designed hydrogel cell supports.The paper describes the possible procedure of FEM calculation of hydrogel materials. The basis of the calculation is to perform a calculation with a common material model. Only after the application of boundary conditions is the material model incrementally changed to the desired. This procedure reduces the risk of non-convergence. In addition, this allows you to choose a solution to which the model converges, if they exist

Multiple Network Hydrogels: A Study of Their Nanoindentation Hardness

Nanoindentation is employed to investigate at the nanoscale the mechanical properties of multiply-interpenetrated N,N-dimethylacrylamide hydrogels cross-linked using N,N′-methylenebis(acrylamide). The main result from these measurements is the determination of the hardness of the materials, that is, their resistance to penetration by the nanoindenter, which increases with network multiplicity, arising from the increase in network compactness with multiplicity. In addition to hardness, the nanoindentation elastic modulus and the percentage of recoverable energy are also determined, and both are found to increase with network multiplicity as well. A general conclusion from this study is that nanoindentation is a facile and fast method for the characterization of a number of mechanical properties of hydrogels, with the important advantage of small amount of sample required for the measurements