Pavlik Lettinga

Soft matter \ Biophysicist

“Break it down as a physicist, build it up as a scientist.”

Research interest

Material properties depend on their building blocks, as well as the environment. Human blood will gel when it is not pumped through the veins, while one can only eat a jelly pudding when it is properly cooled.

In my work, I use building blocks with tuneable features from nature (filamentous virus, F-actin, …) and the lab (colloidal platelets) to study their behaviour in and out of equilibrium. I apply experimental techniques like in situ ultra-fast confocal microscopy and Small Angle neutron and X-ray scattering mainly in combination with shear flow to access information on a single particle as well as ensemble level, thus facilitating direct comparison with theory and computer simulations. With this approach, I aim to expand the field of directed material design, for example aligned hydrogels for cell growth, as well as to understand complex problems such as the break up process of blood aggregates in complex flow. To elucidate the interplay between structure and mechanical response for these complex systems it is not only a prerequisite to break the problem down to understandable pieces, as physicists like me do, but also to build up complexity in a multidisciplinary scientific surrounding.

Research projects

Flow of complex fluids

Bottom up understanding of flowing complex fluids.

Biophysics of the Extracellular Environment

Mimicking and probing properties of extracellular matrices.

With C. Bartic @ KU Leuven

Diffusion in complex landschapes

Understanding the dynamics underlying the plethora of phase transitions in liquid crystals.

Publications and lecture notes


Lectures (mainly in Dutch)


  • Blood news! Margot Belleguez started in fall 2023 her PhD under the title “Investigation of the blood flow in 3D channels that mimic the brain vasculature”. We wish her a lot of fun with the SLE excavated channels in the coming years.
  • Soap news! Manuela Walteros León started in fall 2023 her PhD on “Understanding of microstructure of vesicles for sustainable fabric softness” with Christian Clasen from KU Leuven and Vincenzo Guida from Proctor&Gamble. We wish her a lot of fun with the many methods needed to gain this understanding. 
  • Mehrnaz Babaki graduated the September 11th 2023 @KU Leuven. Congrats and thanks a lot for all the hard work! 
  • Mehrnaz has her first paper published in Biophysical journal : “Competition between deformation and free volume quantified by 3D image analysis of red blood cell”.


  • Winter 2024: talks in Santa Barbara, Ljubljana and Grenoble on the rheology and structure of complex systems using in situ scattering and microscopy.