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Roel Dullens: ‘Cooking, Looking and Tweezing’

Interview with Roel Dullens (Physical Chemistry of Soft Matter group, IMM)

In August 2021, Roel Dullens was appointed Professor in Physical Chemistry of SoftRoel Dullens Matter at the Institute for Molecules and Materials (IMM) at Radboud University. The newly established research group has an interest in the broad field of soft matter, at the interface of chemistry, physics and materials science. The team particularly focuses on the behaviour of so-called colloidal suspensions, which they use to study a wide range of fundamental problems in condensed matter science.

We interviewed Roel Dullens about his scientific background, research focus and goals within the IMM.

What has been your career path so far?

“I studied chemistry in Utrecht, and from my third year onwards I really focused on physical chemistry, mathematics, and physics. In that year I also started my minor project in colloid science, which turned into my main research project. I think my passion for colloids started there and then. After my PhD in Utrecht, during which I studied the structure and dynamics of colloidal hard spheres, I was a Humboldt Fellow in Stuttgart. Then, in 2007, I started my own research group in Oxford, UK. Being an independent group leader, I certainly learned a lot and I enjoyed my time in Oxford and the UK very much.”

What makes it fun for you to go the lab every day?

“I have always had an interest in addressing fundamental and longstanding problems. Also, I really like working with my group members who are creating and uncovering cool things. This process is fantastic.”

How did you end up at Radboud University?

“We have been keeping an eye out for a place closer to our family, and some years ago I already experienced a positive atmosphere in Nijmegen when discussing with some now-IMM colleagues. So, when this position became vacant, I enquired and eventually decided to apply, which resulting in me getting the opportunity to continue my work here in Nijmegen. To this end, we moved our whole lab, including 4 group members - PhD’s and technicians - from Oxford to Nijmegen.”

What is your research focus?

“We study soft condensed matter systems with a particular focus on colloidal suspensions, which we use to study a wide range of fundamental condensed matter science questions. A few examples include: ‘How does a crystal melt into in liquid?’, ‘How do defects in crystals move?’ and ‘How does friction emerge at the particle scale?’”

What exactly are colloidal suspensions?

“In colloidal suspensions, particles with dimensions ranging from a few nanometres to a few micrometres are suspended in a solvent. Daily life examples include mud, milk or blood. These colloidal particles can be used as a versatile model system for atoms and molecules, as their phase behaviour is analogous. However, the typical colloidal length (micrometre) and time (second) scales make it possible to directly ‘look’ at colloidal particles in real space and time with relatively simple optical microscopes. Also, we use chemistry to ‘cook’ these particles and lasers (optical tweezers) to manipulate them.”COLLOIDAL LIQUID CRYSTALS

Colloidal liquid crystals

What projects/topics are you currently working on?

“Currently, we are very interested in the rotational dynamics in dense suspensions of spherical particles, with a particular interest in the emergence of frictional interactions. Also, we are working on the dynamics of grain boundaries in (poly)crystalline materials, on liquid crystals formed by colloidal rods and banana-shaped particles and on the behaviour of driven colloidal systems.”

Teaching, what course will you give?

“I teach the first year Thermodynamics course for bachelor students in the molecular sciences. In this course I can use the experience I gained in Oxford where I was teaching a wide range of topics in physical chemistry. I like teaching and working with students, and I really enjoyed teaching the Thermodynamics course for the first time in the previous quarter.”

What is the societal relevance of your research?

“Whilst in the group we are really focusing on the fundamental side of things, colloidal suspensions find numerous uses in everyday life, as well as many technological and industrial applications. Examples include the food, personal healthcare, paints, and coatings industry.”

What are your future plans in terms of research?

“Currently, we are working hard to get our lab fully up-and-running again so that we can continue our ‘cooking, looking and tweezing’ work on colloidal suspensions. In the future, I also hope to reach out to my colleagues within the IMM and HFML-FELIX and widen our research into directions like biomimetic materials and structural colour, geophysical soft matter, statistical and computational physics of mesoscopic systems, and nano-sized and functionalised soft matter.”

Group website: www.dullenslab.com

Or via the RU website: Physical Chemistry of Soft Matter: Welcome at Physical Chemistry of Soft Matter - Faculty of Science - Institute for Molecules and Materials (ru.nl)

Text: Miriam Heijmerink