Researchers at the National Institute of Standards and Technology (NIST) have demonstrated a microminiaturized device that can make complex viscosity measurementscritical data for a wide variety of fields dealing with things that have to flowon sample sizes as small as a few nanoliters. Currently a table-top prototype, the NIST rheometer could be a particularly valuable tool for biotechnologists studying minute quantities of complex materials that must function in confined spaces.
Viscosity, elasticity and how materials flow when subject to a force is the subject of rheology, and the measurements tell a lot about a complicated material like a gel. Is it more like a liquid or a solid? By how much and under what conditions? The popular toy Silly Putty is a classic example of complex viscoelasticity, bouncing better than a rubber ball under a sharp, sudden force but slumping into a puddle when left alone.
One common way to make dynamic rheology measurements (how behavior changes with the speed or frequency of the applied force) is with a sizeable lab instrument that traps a test sample between a fixed plate and one that moves, and measures how much the thin layer of test material resists being deformed. Typical sample sizes are around a couple of milliliters, which doesn't sound like much, but, says polymer scientist Gordon Christopher, for some researchers it's a whole bunch.
"A lot of people in the biosciences are making very complex designer fluids based on proteins where you might make only 10 milliliters at a time. Polypeptide hydrogels for drug delivery or tissue replacement, for example," Christopher explains. "Their flow behaviors are very complicated and you really need to understand them, but in a traditional rheometer your sample for a single test is a large percentage of what you just spent two months making."
Inspired by a talk by a NIST scientist working on the design of novel nano positioning microelectrom
|Contact: Michael Baum|
National Institute of Standards and Technology (NIST)