Inkjet printing is a technique extensively used in large-scale industrial machines, which offers excellent image resolution and high printing speed. Modern inkjet printers use drop-on-demand systems, where an actuator is used to generate in just one second hundreds of thousands of micron-sized ink droplets moving at large speed.
Achieving excellent print quality is a challenging feat determined by complex physics, and several factors can negatively impact the print quality. For instance, inhomogeneous wetting or dried ink residues at the printer nozzle make the ink droplet deviate from its intended trajectory. Then, the printhead must be tuned and optimized to eject the correct volume of ink; the velocity of the ink droplet and the physical properties of the ink determine whether the droplet will break apart generating small satellite droplets, resulting in a blurred printed pattern.
At FLOW Matters, we combine physics and engineering expertise to create a digital twin of the jetting in the printing system, which is used in physics-aware design and optimization of the printhead. Our numerical simulations are based on the lattice Boltzmann color-gradient model, a method that has been extensively validated on microdroplets dynamics and jetting [1-7]. Using our in-house lattice Boltzmann simulation software, we generate a digital twin of an inkjet printing nozzle. We consider two different scenarios: a clean printing nozzle and a partially occluded printing nozzle. The latter scenario occurs for instance when a hardened ink residue is left on the nozzle wall. In the animation above, we can clearly see how a partial occlusion of the printing nozzle, colored in red, causes the ink droplet to deviate, negatively impacting the print quality; our lattice Boltzmann simulations are capable of accurately predicting the deflected trajectory, assessing the impact of nozzle occlusions on the prints.
[1] R. Benzi, L. Biferale, M. Sbragaglia, S. Succi, and F. Toschi, “Mesoscopic modeling of a two-phase flow in the presence of boundaries: the contact angle”, Phys. Rev. E—Statistical, Nonlinear, and Soft Matter Physics, vol. 74(2), p.021509, 2006.
[2] K.P.N. Datadien, G. Di Staso, H.M.A. Wijshoff, and F. Toschi, “A quantitative comparison of physical accuracy and numerical stability of lattice Boltzmann color gradient and pseudopotential multicomponent models for microfluidic applications”, Comm. Comput. Phys., vol. 32(2), pp. 450–489, 2022.
[3] K.P.N. Datadien, G. Di Staso, and F. Toschi, “Numerical stability analysis for a stationary and translating droplet at extremely low viscosity values using the lattice Boltzmann method color-gradient multi-component model with central moments formulation”, Comm. Comput. Phys., vol. 33(1), pp. 330–348, 2023.
[4] K.P.N. Datadien, G. Di Staso, C. Diddens, H.M.A. Wijshoff, and F. Toschi, “Comparison of lattice Boltzmann, finite element and volume of fluid multicomponent methods for microfluidic flow
problems and the jetting of microdroplets”, Comm. Comput. Phys., vol. 33, pp. 912–936, 2023.
[5] K.P.N. Datadien, “Directional instabilities in microdroplet jetting”, Ph.D. Thesis, Eindhoven University of Technology, 2024.
[6] F. Diotallevi, L. Biferale, S. Chibbaro, A. Lamura, G. Pontrelli, M. Sbragaglia, S. Succi, and F. Toschi, “Capillary filling using lattice Boltzmann equations: The case of multi-phase flows”, The European Physical Journal Special Topics, vol. 166, pp.111-116, 2009.
[7] P. Perlekar, L. Biferale, M. Sbragaglia, S. Srivastava, and F. Toschi, “Droplet size distribution in homogeneous isotropic turbulence”, Phys. Fluids, vol. 24(6), 2012.
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