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I was kind of shocked and amazed by a recent publication in NanoLetters. It seems that viscosity measurements are still difficult. In my ignorance, I had assumed that this was a solved problem. And, just to show the depths of my ignorance, it turns out that you can learn something about a person’s health by measuring the viscosity of their blood. This process is time consuming, as I’ll explain in a moment. Now, thanks to the power of our ability to build little gold-iron alloy helices, these measurements just got a whole lot easier.

Stick around and I’ll tell you about viscosity

Viscosity is a measure of how well things flow. So, for instance, water flows quite easily and rapidly, while some oils flow more slowly—we say that oil is more viscous than water. The study of fluid flow is a very complicated business so, to simplify the problem, you have to ask yourself what is important. For instance, water flowing down a river is probably dominated by the sheer mass of moving fluid. That means you can probably ignore any influence of viscosity and just worry about mass.

On the other hand, when blood reaches the extremities of the body, it is flowing in very fine channels. There is not a lot of mass to the fluid, but the viscous forces between the channel wall and the fluid are enormous. Here, it might be appropriate to ignore anything to do with mass and focus on viscosity. By examining relationships like this, you can build reasonably accurate models of fluid flows without enduring the pain of the full complexity of fluid dynamics equations. But you can only choose what to include in your models if you know the viscosity reasonably accurately.