New paper: “Similarity of internal and external friction: Soft matter frictional instabilities obey mean field dissipation through slip avalanches”

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. […]

New Paper: “Precise Correlation of Contact Area and Forces in the Unstable Friction between a Rough Fluoroelastomer Surface and Borosilicate Glass”

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 Montanuniversit√§t Leoben. […]

Congratulations to Jiho on earning his PhD!

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 […]

Brittle or ductile? Wear reveals the nature of hydrogel damage

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 […]

Local properties of oriented tissues – you can still use indentation!

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 […]

Multifunctionality of insect cuticle: friction and optics

Insects did it first! Inspired by beetle iridescence and a scientist who has studied them (Ainsley Seago), the ABC Lab, the INHS Insect Collection, and the Materials Tribology Lab teamed up to study the multifunctionality of insect cuticle. Back down the evolutionary tree of beetles, some species developed iridescent cuticle, and others did not. This […]

Robust soft robots – use your feet wisely!

As soft robots are the new normal, polydimethylsiloxane, or PDMS, is becoming ubiquitious in labs. You know it as the material that makes “sticky hands” you throw against the wall, and it can be a clear, or slightly cloudy (turbid) soft solid. It can be molded into any shape conceivable, especially shapes with more than […]