A theme shared by all the experiments in my lab is that images contain information about the physical properties of materials. One of my students gave a talk on Monday about his work exploring the fluid environment experienced by swimming microbes (see my earlier post on the microbiome). Planning it beforehand, we were thinking of examples to show illustrating this theme — simple examples not related to zebrafish, lipid membranes, or any of our real research topics — and we decided to use the bottle of Orbitz that I keep on display in my office.
Orbitz is a remarkable “texturally enhanced alternative beverage [1]” sold briefly in the mid 1990’s — consisting of beautiful colored orbs suspended in a clear liquid. What kind of clear liquid? Watch!
Notice that, as the spinning of the bottle ceases, the orange orbs slow down. But: rather than just coming to rest, they move backwards briefly before stopping. Normal liquids (like water) don’t do this. The clear Orbitz liquid has an elastic component that springs back, like a bungee cord! The key point: we can deduce this physical property of the liquid by watching the motion of the orbs. Many polymer gels, and many biological fluids, have this property of “viscoelasticity.” The gel in Orbitz is probably gellan gum and / or xanthan gum — long chains of sugars. I can’t say that I’m tempted to drink it. I’m not alone — it wasn’t a very popular beverage, and didn’t remain on the market for long.
[1] Everything was “alternative” in the mid 1990s. Us kids back then would alternate all night long.
The Eighteenth Elephant 