I am delighted to celebrate the awarding of the 2024 Arthur B. Metzner Early Career Award of the Society of Rheology to Lilian C.
Hsiao, whose citation is shown above.
Lilian was born in Hong Kong and moved with her family to Singapore while she was in elementary school. There she gained an
interest in science, in particular chemistry and physics. Initially planning to do a Bachelor’s degree in Biochemistry at the
University of Wisconsin-Madison, she was cajoled by her friends into Chemical Engineering instead. There she encountered Dan
Klingenberg in her undergraduate transport class, who taught from the famous text by Bird, Stewart and Lightfoot. Finding transport
her favorite subject, she took on an undergraduate research project with Dan on electrorheological fluids. This sparked an interest
in experimental rheology, which was fanned into a passion during her Ph.D. work at the University of Michigan with Mike Solomon on
colloidal suspensions.
At Michigan, Lilian worked with Solomon and Glotzer to combine confocal microscopy and computational simulations to determine
the microstructural basis of stress relaxation in colloidal gels. In this work, Lilian determined the load-bearing portion of
the colloidal gel structure by capturing the position and motion of individual particles in the 3D network, and connecting them
to linear and nonlinear rheological properties. The resulting highly influential work was published in the Proceedings of the
National Academy of Sciences in 2012 and in subsequent papers, including one with Solomon and Furst in the Journal of Rheology
(JoR) in 2014. She also examined the structure of assemblies of anisotropic discoidal particles for which both orientation and
position need to be mapped, and thereby discovered a preferred orientational order in such assemblies, a result published in
Nature Communications.
While still completing her Ph.D., Lilian’s adventurous spirit led her into even more novel territory when she introduced
controlled roughness into particle-particle interactions. Lilian developed a technique for synthesizing poly(methyl methacrylate)
colloids of controllable roughness. Initially frustrated at her inability to find major changes produced in gelation, she raised
the particle concentration, and discovered the profound effect that roughness has on shear thickening and the jamming transition.
Using both confocal imaging and rheological measurements she found the first truly quantitative relationship between rheology of
dense suspensions and particle roughness.
Lilian continued to use microscopy to study the phase behavior of nanoemulsions while she was a postdoctoral scholar with Pat
Doyle at MIT. There she met Safa Jamali, with whom she collaborated to illustrate how frictional contacts affect suspension
rheology. They used confocal rheology and computer simulations to lay a strong, experimentally-grounded basis for how rotational
jamming affects the contact networks found in shear thickening suspensions, which was published in Physical Review Letters and
JoR. Like her earlier work on gels, this work broke new ground in the synthesis and characterization of particles of controlled
roughness, the imaging of these particles at rest and under flow, and the correlation of these structures with rheological properties.
In particular, her 2022 JoR publication reported that rough colloids display unexpected solid-like properties after shear and can
retain memory of their previous state, similar to entangled polymer solutions. This memory is highly dependent on the pre-shear
protocol and microstructural state of the suspension. While most scientific studies have focused on ideally smooth particles,
rough particles are common in industrial practice and are important in jamming, shear thickening, and other problems of great
current interest.
Her keen interest in frictional contacts then led Lilian to initiate an experimental program on tribology. This led her into
contact with Yon Visell at the University of California Santa Barbara, whose interest in haptic technology led Lilian into the
area of tactile materials. This work involves a combination of rheology and tribology to investigate how self-organization of
molecules and fluid flow patterns at the interface alters haptic perception. Her group recently developed and validated a theory
that predicts the lubricated friction of many patterned polymers, including that of robotic and human hands. Such work has many
applications, such as wearable devices, which have gained immense popularity in technologies including augmented reality, electronic
skin, and energy harvesting. Another application is hydrogel dressings tailored for pain and healing management, a technology
being developed by an NC State startup company for which she is the founding scientist.
In her current work, Lilian and collaborators discovered that amphiphilic molecules migrate to the surface of polymers and form
different configurations under shear. This phenomenon provided distinctive changes in the tactile feel as well as the triboelectric
performance of polymeric devices coated with these self-assembled amphiphiles. This is the first study that shows how tactile
perception and energy harvesting performance can both be tuned by a single C = C bond on a small molecule that self-assembles at
the interface, and provides an original and universal physical model for how friction is reduced by changes in the mesostructure
of small organic molecules under pressure. Other active areas of research in her group includes the use of external stimuli to
study gelation, speeding up and slowing down material dynamics, using interfacial mechanics and ionotronic systems for haptic
sensors, and applying her understanding of colloidal self-assembly to create materials that can be used in capturing contaminants
from the environment.
Lilian has a high level of creativity and productivity, with 36 publications in print or accepted for publication, many of which
deal with rheology at the microscopic or macroscopic level. Her research has been featured in >80 invited talks and highlighted
by multiple awards, including the Camille Dreyfus Teacher-Scholar Award, a Sloan Research Fellowship in Chemistry, the ACS
Unilever Award for Outstanding Young Investigator, an NSF CAREER award, and the AAAS Marion Milligan Mason Award.
In addition to her scholarly work, Lilian is actively involved in leadership and planning roles in multiple technical communities
including the American Physical Society (APS) Division of Soft Matter, the American Institute of Chemical Engineers (AIChE), the
American Chemical Society (ACS) Colloid and Surface Science group, and of course The Society of Rheology (SoR). She has
co-organized two national scientific meetings in Raleigh (Society of Rheology 2019 and ACS Colloids 2022), and has contributed
significantly to diversity by enhancing the Wikipedia profiles of underrepresented women and minorities in science. Lilian is a
vibrant and fun-loving colleague, serious about her science, but gregarious and generous in her friendships. Her cute dog, Tora,
can be seen often in her office happily providing companionship to her students and colleagues over rheology discussions.
I and many of my rheological colleagues are proud to have helped in some way Lilian’s development into an outstanding rheologist,
well deserving of the Arthur B. Metzner Early Career Award of The Society of Rheology.