“Properties matter, not the molecules.” – E.L. Cussler.
Our paper on droplet impact with yield-stress fluids on coated substrates is now online:
Sen, S., A. G. Morales, and R. H. Ewoldt, “Viscoplastic drop impact on thin films,” Journal of Fluid Mechanics, 891, A27 (2020). DOI link
We have demonstrated that, as long as the macroscopic rheological flow properties are the same, the microstructural route to those properties itself does not matter. This experimental work demonstrates the generality of a simple dimensionless scaling idea based on forces during drop impact, and its material agnosticity across two vastly different viscoplastic fluids: Laponite clay and Carbopol microgel.
Below is the supplementary video to the paper, showing the various types of impact behaviors observed in the study.
Dr. Chai Saengow will be joining us at Illinois in January 2021 as a Beckman Institute Postdoctoral Fellow.
Read more about Dr. Saengow (Google Scholar here) and the postdoc fellow program via the Beckman Institute and MechSE Department news articles.
Dr. Saengow will collaborate with the research groups of Professor Randy Ewoldt and Professor Amy Wagoner Johnson.
A big vision of our research is to bring design and rheology together.
We’ve just published a collaborative review of this for yield-stress fluids.
- Nelson, A. Z., K. S. Schweizer, B. M. Rauzan, R. G. Nuzzo, J. Vermant, and R. H. Ewoldt, “Designing and transforming yield-stress fluids,” Current Opinion in Solid State and Materials Science, 23 (5), 100758 (2019). DOI link Accepted PDF
Yield-stress fluids are perhaps the most utilized rheologically-complex soft materials in our world today. Designing with this behavior enables applications ranging from the everyday to the extraordinary including drug delivery, food products, batteries, painting, surface coatings, biomaterials, concrete, and other scenarios.
The lead author is lab alum Dr. Arif Nelson, written in collaboration with Ken Schweizer (MatSE, UIUC), Brittany Rauzan (Chemistry, UIUC), Ralph Nuzzo (Chemistry, UIUC), and Jan Vermant (Materials, ETH-Zürich).
From Fig. 3: Materials design encompasses design with a material (performance-to-properties), and design of a material (properties-to-structure).
From Fig. 4: Materials design process illustrated using some of our work in direct-write 3D printing.
“All models are wrong, and some are useful.” -George Box.
Our new collaborative study with colleague Prof. Jon Freund explores how useful the most common non-Newtonian fluid model really is:
Kim, J., P. K. Singh, J. B. Freund, and R. H. Ewoldt, “Uncertainty propagation in simulation predictions of generalized Newtonian fluid flows,” Journal of Non-Newtonian Fluid Mechanics, (2019). DOI link
Free access until Oct 8, 2019 at this link: https://authors.elsevier.com/a/1Zb0c1LkSa4V98
Prof. Ewoldt will visit KU Leuven (Belgium) to lecture at The 17th European School on Rheology 2019 from Sept 1-6.
More information here: https://cit.kuleuven.be/smart/rheoschool
Congratulations to Gaurav Chaudhary for winning an Acta Student Award for his first-author publication:
Chaudhary, G., D. S. Fudge, B. Macias-Rodriguez, and R. H. Ewoldt, “Concentration-independent mechanics and structure of hagfish slime,” Acta Biomaterialia, 79, 123–134 (2018). DOI link
See the MechSE news article for more details.
Gaurav will officially be presented the award at the Acta Symposium during the TMS conference in San Diego in February 2020.
Congratulations, Dr. Corman!
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.