In piezo-acoustic ink-jet print heads, a voltage pulse, applied to the piezoelectric element, induces a deformation of the print head channel creating a pressure wave in the ink, ultimately responsible for the ejection of ink droplets out of the nozzle [1]. Given the extreme accuracy achieved by modern inkjet printers, technological advancement requires a thorough physical understanding of the droplet generation mechanisms and of the subsequent droplet formation process. This project will investigate key physical aspects beyond the formation of inkjet droplets and the influence of physical effects that may interfere with this process [2]. The project will be conducted in close collaboration with Canon Production Printing Netherlands B.V. and in the framework of a larger network of PhD students investigating -with different techniques- several aspects at the basis of ink-jet printing technologies. 

Project description
The selected candidate will perform numerical and theoretical research in order to investigate the fundamental physics beyond the dynamics of droplets formation in ink-jet print-heads. He/she will employ, extend and optimize existing numerical codes in order to perform high-fidelity, fully-3d numerical simulations of droplet jetting, will develop new codes to analyse the data produced, will develop novel, or improve upon existing, theoretical model also on the basis of the numerical investigations. The numerical methods that will be employed will include fully parallelized multiphase Lattice Boltzmann codes, developed in our group [3], as well as open-source codes based on volume of fluid method, like e.g. Gerris or Basilisk. The candidate will investigate full 3d effects, like the breaking of axial-symmetry during the jetting process cause by bubbles entrained in the nozzle. The candidate is expected to be familiar with theoretical methods for the description of multiphase, multicomponent fluids, in particular vapor bubbles, and their numerical implementation in the Lattice Boltzmann method. The candidate is expected to closely interact with Canon Production Printing Netherlands B.V., as well as with other PhD students performing theoretical/experimental studies.

References

[1] Wijshoff, H. (2010). The dynamics of the piezo inkjet printhead operation. Physics Reports, 491(4), 77-177. doi.org/10.1063/1.4990082

[2] Detlef Lohse (2022). Fundamental Fluid Dynamics Challenges in Inkjet Printing. Annual Review of Fluid Mechanics 54(1), 349-382. 10.1146/annurev-fluid-022321-114001

[3] Karun P.N. Datadien, Gianluca Di Staso, Herman M.A. Wijshoff, Federico Toschi (2021). A quantitative comparison of physical accuracy and numerical stability of Lattice Boltzmann color gradient and pseudopotential multicomponent models for microfluidic applications. https://arxiv.org/pdf/2110.05197.pdf

Location 

These projects will be carried out within the Fluids and Flows group at the Department of Applied Physics (https://www.tue.nl/en/research/research-groups/fluids-and-flows/ ) of Eindhoven University of Technology. The PhD candidates will be supervised by prof. F. Toschi.

• We are looking for enthusiastic PhD-students with an excellent background in fluid dynamics and computational physics.
• You have a MSc in (applied) physics or mechanical engineering.
• Knowledge of multiphase fluid dynamics and parallel programming are an asset.
• Close affinity with computational physics is a must.
• As an ideal candidate you should be able to work in a team.
• You also have good written and oral communication skills in English.

A meaningful job in a dynamic and ambitious university, in an interdisciplinary setting and within an international network. You will work on a beautiful, green campus within walking distance of the central train station. In addition, we offer you:

• Full-time employment for four years, with an intermediate evaluation (go/no-go) after nine months. You will spend 10% of your employment on teaching tasks.
• Salary and benefits (such as a pension scheme, paid pregnancy and maternity leave, partially paid parental leave) in accordance with the Collective Labour Agreement for Dutch Universities, scale P (min. €2,770 max. €3,539).
• A year-end bonus of 8.3% and annual vacation pay of 8%.
• High-quality training programs and other support to grow into a self-aware, autonomous scientific researcher. At TU/e we challenge you to take charge of your own learning process.
• An excellent technical infrastructure, on-campus children's day care and sports facilities.
• An allowance for commuting, working from home and internet costs.
• A Staff Immigration Team and a tax compensation scheme (the 30% facility) for international candidates.