Featured Research

from universities, journals, and other organizations

"Smart" Material Grows Dumber With Shrinking Size, Scientist Says

Date:
June 7, 2000
Source:
University Of Illinois At Urbana-Champaign
Summary:
As active materials become increasingly smaller for the next generation of smart materials systems, the need to understand and predict material response becomes critical. At the University of Illinois, an experimental investigation into how the properties and responses of smart materials -- such as piezoelectric ceramics -- change as a function of size has yielded a few surprises.

CHAMPAIGN, Ill. -- As active materials become increasingly smaller for the next generation of smart materials systems, the need to understand and predict material response becomes critical. At the University of Illinois, an experimental investigation into how the properties and responses of smart materials -- such as piezoelectric ceramics -- change as a function of size has yielded a few surprises.

Related Articles


"Both the piezoelectric properties and the dielectric constants of smart materials cast as thin films were found to be strongly dependent on thickness," said Nancy Sottos, a professor of theoretical and applied mechanics. "As the films became thinner, the desired responses became smaller."

Piezoelectric ceramics are commonly used in pressure sensors, microphones and accelerometers. Deposited as thin films, the material can serve as tiny sensors and actuators in microelectromechanical (MEMS) devices, as elements in ultrasonic motors and as switching capacitors for integrated circuitry. While thin films have much better mechanical properties than the bulk ceramics -- for example, films are far less brittle - other physical and electrical properties may change in undesirable ways.

"The properties of piezoelectric films are critical to the quality and the reliability of MEMS devices," Sottos said. "To optimize the performance of thin-film structures, we must first understand the factors that influence those properties."

For their experiments, Sottos and graduate research assistant Lei Lian obtained a number of lead-zirconate-titanate thin films that ranged in thickness from 0.5 to 2.0 microns (a micron is one millionth of a meter). To record the films' tiny displacements (on the order of trillionths of a meter), Sottos and Lian developed a high-resolution, laser Doppler heterodyne interferometric technique.

The measurement scheme is based on the Doppler shift. First, the beam from an argon laser strikes a 40 MHz acousto-optic modulator, which produces two beams and sends them along different arms of the interferometer. One beam then bounces off the sample while the other beam serves as a reference. When the two beams are recombined, the researchers can very accurately extract the displacement signal from the Doppler shift riding on top of the 40 MHz carrier.

"It's clear from our experiments that as the films become thinner and thinner, there is an undesirable decrease in both piezoelectric response and dielectric constant," said Sottos, who published the results in the April 15 issue of the Journal of Applied Physics. "Fortunately, however, it may be possible to avoid these effects by controlling the residual stress in the material."

Significant stresses build up in piezoelectric thin-film structures during the fabrication process, Sottos said. "Changes in the residual stress state might be one major cause for the change in properties with film thickness that we observed. By applying a mechanical stress -- to relieve some of the residual stress -- the response of the film can be greatly enhanced."


Story Source:

The above story is based on materials provided by University Of Illinois At Urbana-Champaign. Note: Materials may be edited for content and length.


Cite This Page:

University Of Illinois At Urbana-Champaign. ""Smart" Material Grows Dumber With Shrinking Size, Scientist Says." ScienceDaily. ScienceDaily, 7 June 2000. <www.sciencedaily.com/releases/2000/06/000602074318.htm>.
University Of Illinois At Urbana-Champaign. (2000, June 7). "Smart" Material Grows Dumber With Shrinking Size, Scientist Says. ScienceDaily. Retrieved December 20, 2014 from www.sciencedaily.com/releases/2000/06/000602074318.htm
University Of Illinois At Urbana-Champaign. ""Smart" Material Grows Dumber With Shrinking Size, Scientist Says." ScienceDaily. www.sciencedaily.com/releases/2000/06/000602074318.htm (accessed December 20, 2014).

Share This


More From ScienceDaily



More Matter & Energy News

Saturday, December 20, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Building Google Into Cars

Building Google Into Cars

Reuters - Business Video Online (Dec. 19, 2014) Google's next Android version could become the standard that'll power your vehicle's entertainment and navigation features, Reuters has learned. Fred Katayama reports. Video provided by Reuters
Powered by NewsLook.com
AP Review: Nikon D750 and GoPro Hero 4

AP Review: Nikon D750 and GoPro Hero 4

AP (Dec. 19, 2014) What to buy an experienced photographer or video shooter? There is some strong gear on the market from Nikon and GoPro. The AP's Ron Harris takes a closer look. (Dec. 19) Video provided by AP
Powered by NewsLook.com
Double-Amputee Becomes First To Move Two Prosthetic Arms With His Mind

Double-Amputee Becomes First To Move Two Prosthetic Arms With His Mind

Buzz60 (Dec. 19, 2014) A double-amputee makes history by becoming the first person to wear and operate two prosthetic arms using only his mind. Jen Markham has the story. Video provided by Buzz60
Powered by NewsLook.com
Navy Unveils Robot Fish

Navy Unveils Robot Fish

Reuters - Light News Video Online (Dec. 18, 2014) The U.S. Navy unveils an underwater device that mimics the movement of a fish. Tara Cleary reports. Video provided by Reuters
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:

Strange & Offbeat Stories


Space & Time

Matter & Energy

Computers & Math

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