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PhD Defence Michiel Hack | Wetting and coalescence: beyond single-phase flows

Wetting and coalescence: beyond single-phase flows

Due to the COVID-19 crisis the PhD defence of Michiel Hack will take place (partly) online.

The PhD defence can be followed by a live stream.

Michiel Hack is a PhD student in the research group Physics of Fluids (POF). His supervisor is prof.dr. J.H. Snoeijer from the Faculty of Science and Technology (S&T).

Multi-phase wetting and coalescence are ubiquitous in nature and technology alike. In particular, a good understanding of wetting and coalescence is crucial for the successful application of inkjet printing technology and for its future development towards, e.g., additive manufacturing. Inspired by phenomena encountered in inkjet printing, this thesis presents several fundamental studies of wetting and coalescence problems. In particular, we focus on the role of liquid substrates and physico-chemical interactions between components in multi-phase systems.

In part I of this thesis we investigate various wetting phenomena. We reveal the mechanism responsible for the interaction between neighbouring drops on a thin liquid substrate. Next, we show that colloidal drops can lead to intricate patterns when deposited on a destabilising liquid substrate. Finally, we show that the contact angle of mixtures of vicinal alkanediols and water is determined by two physico-chemical mechanisms of completely different nature.

Part II of this thesis is concerned with coalescence. We investigate the coalescence of floating oil drops, where the liquid substrate plays a large role in determining the dynamics. Next, we turn our attention to the coalescence of multi-component drops. We reveal the emergence of an elastic singularity in the coalescence of viscoelastic drops. We study the collision between and subsequent coalescence of water drops with ethanol drops, where it turns out that capillary waves play an important role for the shape of the drops during coalescence.

Finally, we present our overall conclusions and suggest several areas that might be of interest for future research and inkjet printing developers.