Advances in the modeling of the liquid transfer between a cavity and a rotating roll

RAFAEL DÍAZ ARIAS; SEBASTIÁN UBAL; DIEGO M. CAMPANA

Córdoba

Congreso; II Brazil-Argentine Microfluidics Congress / V Congreso de Microfluídica Argentina; 2019

FAMAFC, UNC / IFEG, UNC-CONICET

The development of new polymeric materials, like those used in the manufacture of OLED screens and similar devices, enabled the use of traditional printing technologies in the production process: inkjet/drop-on-demand printing, direct-write, gravure printing, among others. The latter one in particular is a continuous, high-resolution and high-throughput production process, with working fluids in a wide range of viscosity values. In order to model this process at the scale of a single cavity ?whose size is in the order of ten microns? the dynamics of viscous flows must be solved, considering the presence of liquid?solid and liquid?gas interfaces, as well as dynamic contact lines. The flow domain deforms continuously between two solid surfaces ?the cavity and the printing substrate? in relative motion. Important advances in the modeling of the process have been achieved in recent years. The complexity of the problem, however, demands further improvements in the modeling. Previous publications have shown that 2D models can adequately capture the general dynamics of the process, demanding far less computational resources than costly 3D simulations. Thus, this work presents our most recent advances in the modeling and simulation of the 2D liquid transfer between a micron-sized cavity and a substrate in relative motion. Specific contributions are a detailed inclusion of inertial effects and an enhanced description of the dynamic contact angle. The former allowed us to show that inertial effects can be important, in spite of the small size of the flow domain. The latter proved to be key in achieving a better description of the wettability and roughness of different substrates used in applications The results obtained in this work enabled the computation of different quantities of great importance in this process, as the fraction of liquid transferred to the substrate, or the fidelity of transfer of the pattern, as a function of the parameters that characterize the process.