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April 29th 2017

Evaporating drops
During her doctoral research, Gelderblom investigated the flow of liquid in evaporating drops. In the initial chapters of her thesis she studied the dynamics of drying drops using theoretical models and gave an answer to the question: what limits the lifetime of an evaporating drop? In close collaboration with Álvaro Gomez Marín (at the time an experimental postdoc at the University of Twente) Gelderblom demonstrated how the theory of evaporating drops can be used to make crystalline structures in both two and three dimensions.

Coffee stains
The highlight of Gelderblom's thesis is the chapter in which she shows how small particles accumulate at the edge of a coffee stain and how this effect can be used to make ordered patterns of particles during the drying of liquid drops. With this research she reached the pages of several Dutch newspapers including the NRC. "Coffee stains develop if drops dry on a somewhat rough surface", says Gelderblom. "As the edge of the drop is fixed, a flow arises within the drop during the evaporation that transports particles in the liquid to the edge." As this flow is not constant the typical pattern of particles from a dried up drop is created: ordered at the edge but more chaotic towards the middle.

Since June 2013 Gelderblom has been employed by FOM as a group leader in the Industrial Partnership Programme 'Fundamental fluid dynamics challenges in extreme ultraviolet lithography', a collaboration between the Physics of Fluids group at the Universiy of Twente and ASML. She is searching for the mechanism behind the fragmentation of falling drops. "" We are observing what happens if such a drop is hit by a laser beam and we are trying to unravel under which conditions a drop will fragment if it hits a surface," says Gelderblom. "What I like about the physics of fluids is that you can scale problems so well. Using a model of water droplets and the correct limiting conditions we can simulate and investigate real situations.

Contact information
Dr Hanneke Gelderblom, +31 (0)53 489 59 55

Hanneke Gelderblom's thesis can be found on the website of the University of Twente.

On YouTube you can listen to a fragment (in Dutch) of the interview with Hanneke Gelderblom from the FOM Year Book 2013.

You can also view a video about the coffee strain research.