Manuka Honey & Thixotropy
February 28th, 2021
I hope everyone had a happy Lunar New Year! It has been about a year since I started the Soft Matter Kitchen and so I wanted to kick off a new style of video presentation that I’ll be including more of going forward. The video below is actually something that has existed in various unfinished forms since near the end of my PhD at the University of Illinois. With the support of the Society of Rheology, I’m happy to finally be able to present a demonstration of the rheological concept of thixotropy, featuring Professor Gerry Fuller from Stanford University.
Thixotropy refers to a time-dependent decrease in viscosity as stress is applied to a fluid, followed by recovery of the viscosity after the stress is removed. The presence of thixotropy or a “thixotropic recovery time” is therefore dependent on the material being shear-thinning. Ideal shear-thinning materials instantaneously decrease or recover their viscosity in response to different levels of shear stress. As the video shows, however, materials like the manuka honey which have significant thixotropic recovery times can have their material structure gradually broken down by flow and then remain at a low viscosity long after the shear stress has been removed.