‘Lab on a chip’ micro rheometer to improve viscosity tests dramatically

WASHINGTON - Researchers at the National Institute of Standards and Technology (NIST) have created a miniature device that can make complex viscosity measurements on sample sizes as small as a few nanoliters.

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.

“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,” polymer scientist Gordon Christopher said.

“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,” he added.

Kalman Migler and his colleagues created the rheometer that is about one-twentieth the size of a postage stamp.

“With our device, if you gave me a milliliter of sample, I could give you back hundreds of tests,” Christopher said.

Plus, when the material is meant to be used in a confined region like a blood vessel or the interior of a cell-or must be injected through a thin needle-understanding the flow characteristics of small amounts in a small space is more important than knowing how it behaves in bulk.

In a more polished version, according to the research team, the necessary sensors could be included on the chip and the entire instrument reduced to a handheld device for, e.g., quality control measurements on a plant floor.

The NIST MEMS dynamic rheometer is described in a new paper in Lab on a Chip. (ANI)