When you’re small, liquids behave like slippery solids
We think we're pretty familiar with how ordinary liquids behave, but it turns out that some of the basic things we know are no longer true when we look at these liquids on short enough length scales and fast enough time scales. The liquids start to behave more like solids, pushing back when you push on them, and slipping across solid surfaces instead of being dragged along. Click to ride the tiny-but-mighty new wave of nanofluidics!
Use a laser pointer to measure the thickness of your hair!
Have you ever wondered how scientists can accurately measure the size of very small objects like molecules, nanoparticles, and parts of cells? Scientists are continually finding new ways to do this, and one powerful tool they use is light scattering. When an incoming beam of light hits an object, the light "scatters," or breaks into separate streams that form different patterns depending on the size of the object. This incoming light might be visible light, like the light we see from the sun, or it might be higher-energy light like X-rays. The light from commercial laser pointers, it turns out, is perfectly suited to measure the size of a human hair!
What is Viscosity?
The term may be unfamiliar, but we all have a sense for viscosity. We often think of it colloquially as the “thickness” of a fluid. It’s the property that makes honey pour so differently from water. Fluid dynamicists – scientists and engineers who study how liquids and gases move – tend to think of viscosity in terms of a fluid’s resistance to flowing or changing its shape.