News

Prof. Ewoldt delivered a plenary lecture on “Design of Yield-Stress Fluids” at the 8th International Symposium on Food Rheology and Structure in Zürich, Switzerland, on June 18, 2019.

This especially highlights the work of lab alum Dr. Arif Nelson, and our upcoming paper in Current Opinion in Solid State and Materials Science which was written in collaboration with Ken Schweizer (MatSE, UIUC), Brittany Rauzan (Chemistry, UIUC), Ralph Nuzzo (Chemistry, UIUC), and Jan Vermant (Materials, ETH-Zürich).

PDF of lecture slides available here.

 

Congratulations, Dr. Chaudhary!

Our paper “Thermoresponsive stiffening with microgel particles in a semiflexible fibrin network” in collaboration with Schweizer and Braun groups (Material Science, Illinois) is now published in Macromolecules.

We introduce a new paradigm for designing soft materials with large changes of reversibly triggerable stiffness by combining semiflexible polymers that stiffen in tension with microgel polymer particles that massively deswell with heating.

Microgel colloidal particles of poly(N-isopropylacrylamide) (pNIPAM) are embedded in semiflexible biopolymer networks of fibrin. Individual components soften with temperature. When combined, the composite material modulus reversibly stiffens up to 10x in some cases. The developed micromechanical model quantifies the hypothesis of microgel-induced polymer network deformation and is consistent with experimental trends.

Join us at an upcoming rheology short course in Palo Alto, CA June 11-13.

Prof. Ewoldt with join Profs. Macosko (Minnesota), Fuller (Stanford), McKinley (MIT), and Zia (Stanford) to deliver this 3-day introductory course on rheology on Stanford University’s campus.

Great for practicing engineers, scientists, and technicians. Faculty and student attendance is also encouraged with an academic discount.

Congratulations, Dr. Singh!

Our recently published work in Physics of Fluids, “Time-strain separability in medium-amplitude oscillatory shear”, is chosen as an Editor’s Pick.

This study resolves the questions about what is meant by a time-strain separable (TSS) response in medium-amplitude oscillatory shear (MAOS), and how the linear viscoelastic (LVE) relaxation spectrum affects the frequency-dependent behavior of the TSS MAOS material functions. The results show that weakly-nonlinear oscillatory perturbations from the material equilibrium state are substantially more sensitive than the LVE response to the distribution of terminal relaxation times.

The article, dedicated to Prof. Robert Byron Bird on the occasion of his 95th birthday, is available here: DOI link  Accepted PDF

Nature posted a Research Highlight of our collaborative work with Chemistry @ Illinois Prof. Steve Zimmerman and others.

Our work in JACS reports a new class of polymeric materials that rapidly degrade with an acid trigger.

The Ewoldt group contributions involved rheological measurement of degrading mechanical properties and mathematical modeling to infer molecular reaction rates from rheology.

The rapid self-degradation was found to be governed by an autocatalytic reaction, resulting in a governing differential equation known as the “logistic equation” (interestingly, this is also used for some human population growth models).

Miller et al., “Acid-triggered, acid-generating, and self-amplifying degradable polymers,”
Journal of the American Chemical Society (2019).
http://doi.org/10.1021/jacs.8b07705

 

 

Science Magazine highlights our work with Prof. Jean-Luc Thiffeault (UW Madison) on “Unraveling hagfish slime”.

We calculate how the thread components can unravel in a fraction of a second during an attack due to viscous drag of the surrounding flow. The article in the Journal of The Royal Society is here.

Other press reports can be found here: New Scientist, Popular Science, Newsweek, Phys.org, UW Madison, ScienceDaily, arsTechnica

Enjoy the following demonstration of the force-induced unraveling of a hagfish skein (~ 100 micron)

 

Samya Sen lead the making of our video entry to the 2018 Gallery of Fluid Motion, part of the APS Division of Fluid Dynamics Annual Meeting, to be held in Atlanta in November 2018.

We’ve posted it to our YouTube channel, shown here:

Congratulations to Rebecca! Our paper “Mechanically active materials in three-dimensional mesostructures,” in collaboration with Xin Ning, John Rogers, et al., is now online in Science Advances, and highlighted as a featured article.

The paper is available here: https://doi.org/10.1126/sciadv.aat8313

The key idea is to combine advanced manufacturing and mechanics to integrate multiple, independently addressable piezoelectric thin-film actuators into complex, 3D mesostructures. Among the many possible uses, in this work we demonstrate the ability to measure viscosity and density of  surrounding fluids.