Many researchers are aware that hydrogels, even a single kind of hydrogel (polyacrylamide) can be designed to have properties that range from brittle to viscoelastic. It’s truly a versatile material! As hydrogels are being considered as replacements for cartilage in the body, they need to be able to take a beating: they can’t break under […]
We had the nice chance to collaborate with Kyle Schulze at Auburn University to put together a review. Check it out to get some good resources for your next paper or proposal! https://rdcu.be/b9jwq
Hydrogels are the next “engineering material” that we need new textbooks for, to teach the next generation of engineers to design with them. Shabnam’s work contributes directly to that, and over the past 4 years she has discovered that the material nature of the hydrogel determines how it wears away — sometimes it acts brittle, […]
We usually think of hydrogels as slippery and wet — that’s their definition! But if a probe pushes on them to a higher pressure before applying lateral slip, that high pressure causes unstable friction, or stick-slip (just like the elastomer in our prior post!). So even inherently low-friction materials relieve interfacial strain in extreme ways. […]
Last year I had the privilege of hosting the now Dr. Chao Wang in my lab to use our optical in situ microtribometer to study the stick-slip behavior of seal elastomers. He obtained a supporting fellowship from the Austrian Marshall Plan Foundation, and used this work toward his PhD in Polymer Tribology from Montanuniversität Leoben. […]
We describe the resistance to slip of an interface as friction, and the origin of that friction can vary widely: roughness, plasticity, lubrication, temperature, etc. Some of those originating mechanisms can also change with time: asperities flattening, lubricating migration, or other things. The way that people have tried to quantify those changing mechanisms is to […]
We’ve had a bit of a hiatus in publicizing our work, but we’re back! The first big congratulations goes to Jiho, who defended his dissertation in the middle of a raging worldwide pandemic. He successfully presented from his residence, his dissertation entitled “SOFT HYDRATED SLIDING INTERFACES AS COMPLEX FLUIDS.” Jiho moved very quickly to a […]
You might see stress when you look in the mirror, but in a material that is just flexing a little (elastically), you can’t see the stress. You have to go back to TAM 251 (Solid Mechanics) and ME 330 (Materials) to derive the definitions and apply with confidence. But in ME 472 this week, we’re […]
The more you learn about hydrogels, the weirder they become. They take their shape from water, but act as a brittle solid when you try to break them in your hands. However, they are also quite stretchy. These contradictions are sorted out a bit in Shab’s new paper “Brittle or Ductile? Abrasive Wear of Polyacrylamide […]
Microindentation is a useful technique for assessing the local properties of soft materials. But applying an appropriate contact model and extracting those properties is a more complex matter, especially for anisotropic biological tissues like tendon. Do not despair! Jiho worked with the Wagoner Johnson Lab to demonstrate the elliptical contact areas between a spherical probe […]