I am honored to introduce the readers of the Bulletin to Jan Vermant, the recipient of the 2021 Bingham Medal of The Society of Rheology. I have known Jan since he was a graduate student and was
his postdoc mentor. The two of us have collaborated over the years on problems related to interfacial rheology. I fondly recall one of my first meetings with Jan in 1994. He arrived at the
Brussels’ train station to collect me along with his wife, Karin, in a “European-appropriate-sized” car only to discover that I my luggage included a mountain bike. Jan is a problem solver and
quickly set things in motion to get me over to my hotel.
Jan is one of the finest rheologists worldwide and he is a leading figure in colloid and interfacial dynamics. His work includes important findings on dispersion rheology, and he is recognized for
his innovative and foundational contributions to interfacial rheology. Indeed, he has profoundly influenced this latter topic through the development of new experimental methods, morphological control
of model complex interfaces, and theoretical analysis of non-Newtonian interfacial flows. His outstanding accomplishments were recognized by the leadership of the ETH and he moved to that institution
to hold the first chair in soft materials. In 2019 Jan received the Weissenberg Award from the European Society of Rheology, one of the highest accolades of our profession.
What is most striking about Jan’s research accomplishments is the combination of the diversity of physical phenomena and the depth of these investigations. Jan’s experiments investigating the coupling
of particle shape and capillarity to drive remarkable pattern formations by colloidal particles are a wonderful example of his ability to recognize key physical variables controlling physical phenomena
in interfacial science. His 2011 paper in JACS is truly a tour de force on the discovery of new pathways to generate elaborate, chainlike structures.
Jan’s work on bacterial swarming is an impressive application of interfacial flow physics and optical microscopy that led to the recognition of a mechanism of colony transport through Marangoni stresses.
This work is beautifully captured in his 2011 Soft Matter paper on the subject, which is another example of Jan’s ability to couple experiment with theory.
Understanding and controlling the composition and dynamics of emulsions are formidable challenges in the field of liquid-liquid interfaces, with profound technological implications. Jan has contributed
significantly to the field and a jewel of the crown is undoubtedly where he been demonstrated, for the first time, that it is possible to control both surface coverage and composition of droplet interfaces
at will (Nature Comm. 2018).
Jan has made lasting contributions to instrument design in interfacial rheology. Most notable is the development of the “double-wall ring” interfacial shear rheometer, which allows one to convert conventional
rotational rheometers into highly sensitive devices for the measurement of surface rheometric material functions. This device, which is now commercially available, has been adopted by numerous laboratories
world-wide to address problems in emulsion, foam, and solution stability.
While a graduate student under the mentorship of Jan Mewis of KU Leuven, a part of Jan’s thesis concerned superposition rheometry, where steady shear and oscillatory shear are combined. The tools available
at that time made this application difficult. Jan is not one to let problems unfinished and, recently, he has taken advantage of the flexibility of modern rheometers to demonstrate the striking ability of
superposition rheometry to judiciously reveal flow-microstructure couplings (Phys. Rev. Lett. 2015).
Through targeted collaborations, Jan and his collaborators are also responsible for some of the finest measurements of interaction forces existing between particles trapped at oil/water interfaces. These
forces are fundamental to understanding mechanisms of particle stabilization in Pickering emulsions and have been the source of debate for over a decade. This body of work is an important demonstration of
Jan’s authoritative grasp of colloidal physics and judicious experiments coming from his collaboration with Eric Furst’s group. Another example is his collaboration with John Brady to experimentally test
the concept of “swimming pressure”. This was accomplished means of acoustic trapping of active matter with John’s student, Sho Takatori (Nature Comm. 2016). His collaboration with
Pier Luca Maffettone and Chris Macosko resulted in a very nice demonstration of using rheology to quantify dispersion stability in nanocomposite materials (JoR 2007).
Jan was raised in the Belgian village of Bonheiden by his father, who was an electrochemist and university professor, and his mother, who still operates a lace school and museum in town. I highly recommend
visiting this phenomenal museum. His mother has relayed many stories to Jan’s wife, Karin, about Jan’s earliest ventures in rheology. This one is especially revealing: “when he was about 10 years old, his
mom found strange little plastic bags in the freezer. They contained a weird suspension and, when she asked Jan what was in them, he mentioned that it was ‘snowball glue’. He had mixed snow with glue in
order for the snow to stick better together (and he was sure all of his friends would be super excited once it would work)!”
Jan is a student of Belgian literature – in the form of Tintin and Asterix comic books. Although there is no question that Tintin is (was) an adventurous Belgian boy, Jan is only too happy to rise in
defense of the assertion that the famous Gaullist warrior, Asterix, is of Belgian and not French origin. Jan’s father was an avid sailor and passed this passion onto Jan. Indeed, while a university
student, Jan was a world-class, competitive racer (he achieved a world ranking of 30!). Favorite vacations of the Vermant family are all-hands-on-deck expeditions off the shores of Belgium and throughout
the Mediterranean. Jan met his wife, Karin, while they were both chemical engineering undergraduates at KU Leuven. I have heard different stories about which person achieved the higher grades.
My wife, Mary, and I have enjoyed the company of Jan’s children, and both spent a summer in our home while carrying out research internships in my laboratory. Marie graduated from KU Leuven’s Faculty
of Medicine and Joannes is studying pure mathematics at the same university. They are both happy to regale you with stories of Jan – like the time he put his foot through the living room ceiling while
working in the attic. Joannes is also pleased to point out he is now taller than his father.
The community of rheologists is most fortunate to enjoy the leadership and scholarship of Jan Vermant. His work includes seminal discoveries that have brought understanding and fundamental insight to
problems at the forefront of rheology, and he represents the qualities one seeks in a Bingham Medalist.