Novel approach to measuring surface properties
25 Jul 2013
A study led by technology institute NIST has demonstrated an instrument capable of making sensitive measurements.
The instrument, which measures the mechanical properties of thin films, has been designed by the National Institute of Standards and Technology (NIST) and the University of North Carolina.
A unique feature of the instrument is its ability to gauge the depth of an indentation in a test surface with no contact of the surface other than the probe itself.
The team wanted to create a tool that measured material hardness without forcing an indenter into the test specimen.
The nanoindenter is capable of applying forces up to 150 millinewtons
NIST researcher Douglas Smith
NIST researcher Douglas Smith said: “We are trying to get the most accurate measurement possible of how far the indenter tip penetrates into the surface of the specimen, and how much force it took to push it in that far.We record this continuously. It’s called ’instrumented indentation testing’.”
At the nanoscale you need to know exactly where the surface of the test specimen is relative to the indenter’s tip.
“For example, if you want to look at creep in polymer that reference point itself is going to be creeping into the polymer just under its own contact force. That’s an error you don’t know and can’t correct for,” added Smith.
The nanoindenter is capable of applying forces up to 150 millinewtons, taking readings a thousand times a second, with an uncertainty lower than 2 micronewtons, and while measuring tip penetration up to 10 micrometres to within about 0.4 nanometres.
Its primary use, said Smith, will be in the development of reference materials that can be used to calibrate other instrumented indenters.
