Scaling Friction Down to the Nano/Micro Realm

May 28, 2004
3D computer image of a eliptical tip used to make friction measurements

An improved method for correcting nano- and micro-scale friction measurements has been developed by researchers at the National Institute of Standards and Technology (NIST). The new technique should help designers produce more durable micro- and nano-devices with moving parts, such as tiny motors, positioning devices or encoders.

Friction measurements made at the micro- and nano-scale can differ substantially due to changes in applied load. In a series of experiments described by nanotribologist Stephen Hsu at a technical meeting held May 17-20 in Toronto,* NIST scientists confirmed that many of the measured differences appear to be caused by unintended scratching of the surface by the sharp tips used in making the measurements themselves.

The NIST team used a specially designed friction tester developed jointly by NIST and Hysitron Inc. of Minneapolis. A carefully calibrated force was applied to diamond tips having a range of sizes. Friction forces were then measured as each tip was slid across a very smooth surface of silicon. Friction at the macroscopic scale is usually straightforward—doubling the force between two objects produces twice the friction. However, work at NIST and elsewhere has shown that friction at the microscale does not always obey this scaling rule. Forces greater than about 2 milliNewton** produced substantially greater friction values than expected.

Images of the test surface made with an atomic force microscope confirmed that unintentional scratching produced the extra friction. To correct for this effect, NIST researchers developed a way to measure precisely the size, shape and orientation of the diamond tips so that friction forces caused by "plowing" can be subtracted to produce a more accurate final measurement.

Find the original press release on NIST web-site.

______________________

*The work was presented at the Society of Tribology and Lubrication Engineers annual meeting.
** For comparison, a penny held against Earth's gravity produces a force of about 25 milliNewtons.

Explore further: A stretchy mesh heater for sore muscles

Related Stories

JILA's short, flexible, reusable AFM probe

Apr 09, 2014

(Phys.org) —JILA researchers have engineered a short, flexible, reusable probe for the atomic force microscope (AFM) that enables state-of-the-art precision and stability in picoscale force measurements. ...

At the nanoscale, graphite can turn friction upside down

Oct 17, 2012

(Phys.org)—If you ease up on a pencil, does it slide more easily? Sure. But maybe not if the tip is sharpened down to nanoscale dimensions. A team of researchers at the National Institute of Standards and Technology (NIST) ...

Recommended for you

A stretchy mesh heater for sore muscles

Jul 03, 2015

If you suffer from chronic muscle pain a doctor will likely recommend for you to apply heat to the injury. But how do you effectively wrap that heat around a joint? Korean Scientists at the Center for Nanoparticle ...

Polymer mold makes perfect silicon nanostructures

Jul 03, 2015

Using molds to shape things is as old as humanity. In the Bronze Age, the copper-tin alloy was melted and cast into weapons in ceramic molds. Today, injection and extrusion molding shape hot liquids into ...

Better memory with faster lasers

Jul 02, 2015

DVDs and Blu-ray disks contain so-called phase-change materials that morph from one atomic state to another after being struck with pulses of laser light, with data "recorded" in those two atomic states. ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.