Featured Research

from universities, journals, and other organizations

Depth charge: Using atomic force microscopy to study subsurface structures

Date:
June 28, 2010
Source:
National Institute of Standards and Technology (NIST)
Summary:
Researchers have shown that under the right circumstances, surface science instruments such as the atomic force microscope can deliver valuable data about sub-surface conditions.

Electric force microscopy can be used to detail structures well below the surface. Left, AFM height image showing the surface of a polyimide/carbon nanotube composite. Right, EFM image revealing the curved lines of subsurface nanotubes.
Credit: NIST

Over the past couple of decades, atomic force microscopy (AFM) has emerged as a powerful tool for imaging surfaces at astonishing resolutions -- fractions of a nanometer in some cases. But suppose you're more concerned with what lies below the surface? Researchers at the National Institute of Standards and Technology (NIST) have shown that under the right circumstances, surface science instruments such as the AFM can deliver valuable data about sub-surface conditions.

Their recently published work with colleagues from the National Aeronautics and Space Administration (NASA), National Institute of Aerospace, University of Virginia and University of Missouri could be particularly useful in the design and manufacture of nanostructured composite materials. Engineers are studying advanced materials that mix carbon nanotubes in a polymer base for a wide variety of high-performance applications because of the unique properties, such as superior strength and electrical conductance, added by the nanotubes. The material chosen by the research team as their test case, for example, is being studied by NASA for use in spacecraft actuators because it may outperform the heavier ceramics now used.

But, says NIST materials scientist Minhua Zhao, "one of the critical issues to study is how the carbon nanotubes are distributed within the composite without actually breaking the part. There are very few techniques available for this kind of non-destructive study." Zhao and his colleagues decided to try an unusual application of atomic force microscopy.

The AFM is actually a family of instruments working on the same basic principal: a delicate needle-like point hovers just above the surface to be profiled and responds to weak, atomic-level forces. A typical AFM senses so-called "van der Waals forces," very short-range forces exerted by molecules or atoms. This restricts the instrument to the surface of samples.

Instead, the team used an AFM designed to use the stronger, longer-range electrostatic force (technically an EFM), measuring the interaction between the probe tip and a charged plate beneath the composite sample. What makes it work, says Zhao, is that the nanotubes are electrical conductors with high dielectric constant (a measure of how the material affects an electric field), but the polymer is a low dielectric constant material. Such huge dielectric constant differences between nanotubes and the polymer is the key to the success of this technique, and with properly chosen voltages the nanotubes show up as finely detailed fibers dispersed below the composite's surface.

The goal, according to Zhao, is to control the process well enough to allow quantitative measurements. At present the group can discriminate different concentrations of carbon nanotubes in the polymer, determine conductive networks of the nanotubes and map electric potential distribution of the nanotubes below the surface. But the measurement is quite tricky, many factors, including probe shape and even humidity affect the electrostatic force.

The team used a specially designed probe tip and a patented, NIST-designed AFM humidity chamber. An interesting, not yet fully understood effect, says Zhao, is that increasing the voltage between the probe and the sample at some point causes the image contrast to invert, dark regions becoming light and vice versa. The team is studying the mechanism of such contrast inversion.

"We are still optimizing this EFM technique for subsurface imaging," says Zhao. "If the depth of nanostructures located from the film surface can be determined quantitatively, this technique will be a powerful tool for nondestructive subsurface imaging of high dielectric nanostructures in a low dielectric matrix, with a broad range of applications in nanotechnology."


Story Source:

The above story is based on materials provided by National Institute of Standards and Technology (NIST). Note: Materials may be edited for content and length.


Journal Reference:

  1. Minhua Zhao, Xiaohong Gu, Sharon E Lowther, Cheol Park, Y C Jean, Tinh Nguyen. Subsurface characterization of carbon nanotubes in polymer composites via quantitative electric force microscopy. Nanotechnology, 2010; 21 (22): 225702 DOI: 10.1088/0957-4484/21/22/225702

Cite This Page:

National Institute of Standards and Technology (NIST). "Depth charge: Using atomic force microscopy to study subsurface structures." ScienceDaily. ScienceDaily, 28 June 2010. <www.sciencedaily.com/releases/2010/06/100624092530.htm>.
National Institute of Standards and Technology (NIST). (2010, June 28). Depth charge: Using atomic force microscopy to study subsurface structures. ScienceDaily. Retrieved April 19, 2014 from www.sciencedaily.com/releases/2010/06/100624092530.htm
National Institute of Standards and Technology (NIST). "Depth charge: Using atomic force microscopy to study subsurface structures." ScienceDaily. www.sciencedaily.com/releases/2010/06/100624092530.htm (accessed April 19, 2014).

Share This



More Matter & Energy News

Saturday, April 19, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Small Reactors Could Be Future of Nuclear Energy

Small Reactors Could Be Future of Nuclear Energy

AP (Apr. 17, 2014) After the Fukushima nuclear disaster, the industry fell under intense scrutiny. Now, small underground nuclear power plants are being considered as the possible future of the nuclear energy. (April 17) Video provided by AP
Powered by NewsLook.com
Horseless Carriage Introduced at NY Auto Show

Horseless Carriage Introduced at NY Auto Show

AP (Apr. 17, 2014) An electric car that proponents hope will replace horse-drawn carriages in New York City has also been revealed at the auto show. (Apr. 17) Video provided by AP
Powered by NewsLook.com
Honda's New ASIMO Robot, More Human-Like Than Ever

Honda's New ASIMO Robot, More Human-Like Than Ever

AFP (Apr. 17, 2014) It walks and runs, even up and down stairs. It can open a bottle and serve a drink, and politely tries to shake hands with a stranger. Meet the latest ASIMO, Honda's humanoid robot. Duration: 00:54 Video provided by AFP
Powered by NewsLook.com
German Researchers Crack Samsung's Fingerprint Scanner

German Researchers Crack Samsung's Fingerprint Scanner

Newsy (Apr. 16, 2014) German researchers have used a fake fingerprint made from glue to bypass the fingerprint security system on Samsung's new Galaxy S5 smartphone. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins