Featured Research

from universities, journals, and other organizations

New Polymers Engineered To Change Their Stiffness And Strength When Exposed To Liquids

Date:
March 10, 2008
Source:
Case Western Reserve University
Summary:
Scientists have created a new type of polymer that displays chemoresponsive mechanic adaptability -- meaning the polymer can change from hard to soft plastic and vice versa in seconds when exposed to liquid. "The materials on which we reported in Science were designed to change from a hard plastic -- think of a CD case -- to a soft rubber when brought in contact with water," according to one of the researchers.

Scanning electron microscopy image of a bio-inspired chemo-responsive nanocomposite with adaptive mechanical properties.
Credit: Case Western Reserve University

An interdisciplinary team of researchers from the departments of macromolecular science and engineering and biomedical engineering at the Case School of Engineering and the Louis Stokes Cleveland Department of Veterans Affairs Medical Center has published ground-breaking work on a new type of polymer that displays chemoresponsive mechanic adaptability -- meaning the polymer can change from hard to soft plastic and vice versa in seconds when exposed to liquid.

Jeffrey R. Capadona, associate investigator at the VA's Advanced Platform Technology (APT) Center, graduate student Kadhiravan Shanmuganathan, and Case Western Reserve University professors and APT investigators Dustin Tyler (biomedical engineering), Stuart Rowan (macromolecular science) and Christoph Weder (macromolecular science) have unveiled a radically new approach for developing polymer nanocomposites which alter their mechanical properties when exposed to certain chemical stimuli.

"We can engineer these new polymers to change their mechanical properties -- in particular stiffness and strength -- in a programmed fashion when exposed to a specific chemical," says Weder, one of the senior authors of the paper.*

"The materials on which we reported in Science were designed to change from a hard plastic -- think of a CD case -- to a soft rubber when brought in contact with water," adds Rowan, who has been Weder's partner on the project for almost six years.

"Our new materials were tailored to respond specifically to water and to exhibit minimal swelling, so they don't soak up water like a sponge," saud Shanmuganathan.

In their new approach, the team used a biomimetic approach -- or mimicking biology -- copying nature's design found in the skin of sea cucumbers.

"These creatures can reversibly and quickly change the stiffness of their skin. Normally it is very soft, but, for example, in response to a threat, the animal can activate its 'body armor' by hardening its skin," explains Capadona, who has a sea cucumber in his aquarium. Marine biologists have shown in earlier studies that the switching effect in the biological tissue is derived from a distinct nanocomposite structure in which highly rigid collagen nanofibers are embedded in a soft connective tissue. The stiffness is mediated by specific chemicals that are secreted by the animal's nervous system and which control the interactions among the collagen nanofibers. When connected, the nanofibers form a reinforcing network which increases the overall stiffness of the material considerably, when compared to the disconnected (soft) state.

Building on their recent success on the fabrication of artificial polymer nanocomposites containing rigid cellulose nanofibers, which earned them the December 2007 cover of Nature Nanotechnology, the team mimicked the architecture nature 'designed' for the sea cucumbers and created artificial materials that display similar mechanical morphing characteristics.

The Case Western Reserve/VA team is specifically interested in using such dynamic mechanical materials in biomedical applications, for example as adaptive substrates for intracortical microelectrodes. These devices are being developed as part of 'artificial nervous systems' that have the potential to help treat patients that suffer from medical conditions such as Parkinson's disease, stroke or spinal cord injuries, i.e., disorders in which the body's interface to the brain is compromised. A problem observed in experimental studies is that the quality of the brain signals recorded by such microelectrodes usually degrades within a few months after implantation, making chronic applications challenging.

One hypothesis for this failure is that the high stiffness of these electrodes, which is required for their insertion, causes damage to the surrounding, very soft brain tissue over time. "We believe that electrodes that use mechanically adaptive polymer as substrate could alleviate this problem" explains Dustin Tyler, who specializes in neural interfacing and functional electrical stimulation. The development and testing of experimental microelectrodes that involve the new adaptive materials is currently underway. "That's why we designed our first materials to respond to water" explains Weder. "This allows the rigid electrodes to become soft when implanted into the water-rich brain" he adds.

*The research was published in the March 7, 2008, issue of Science.


Story Source:

The above story is based on materials provided by Case Western Reserve University. Note: Materials may be edited for content and length.


Cite This Page:

Case Western Reserve University. "New Polymers Engineered To Change Their Stiffness And Strength When Exposed To Liquids." ScienceDaily. ScienceDaily, 10 March 2008. <www.sciencedaily.com/releases/2008/03/080306183131.htm>.
Case Western Reserve University. (2008, March 10). New Polymers Engineered To Change Their Stiffness And Strength When Exposed To Liquids. ScienceDaily. Retrieved April 23, 2014 from www.sciencedaily.com/releases/2008/03/080306183131.htm
Case Western Reserve University. "New Polymers Engineered To Change Their Stiffness And Strength When Exposed To Liquids." ScienceDaily. www.sciencedaily.com/releases/2008/03/080306183131.htm (accessed April 23, 2014).

Share This



More Matter & Energy News

Wednesday, April 23, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Air Force: $4.2B Saved from Grounding A-10s

Air Force: $4.2B Saved from Grounding A-10s

AP (Apr. 23, 2014) Speaking about the future of the United States Air Force, Chief of Staff Gen. Mark Welsh says the choice to divest the A-10 fleet was logical and least impactful. (April 23) Video provided by AP
Powered by NewsLook.com
Is North Korea Planning Nuclear Test #4?

Is North Korea Planning Nuclear Test #4?

Newsy (Apr. 22, 2014) South Korean officials say North Korea is preparing to conduct another nuclear test, but is Pyongyang just bluffing this time? Video provided by Newsy
Powered by NewsLook.com
China Falls for 4x4s at Beijing Auto Show

China Falls for 4x4s at Beijing Auto Show

AFP (Apr. 22, 2014) The urban 4x4 is the latest must-have for Chinese drivers, whose conversion to the cult of the SUV is the talking point of this year's Beijing auto show. Duration: 00:40 Video provided by AFP
Powered by NewsLook.com
Hagel Gets Preview of New High-Tech Projects

Hagel Gets Preview of New High-Tech Projects

AP (Apr. 22, 2014) Defense Secretary Chuck Hagel is given hands-on demonstrations Tuesday of some of the newest research from DARPA _ the military's Defense Advanced Research Projects Agency program. (April 22) Video provided by AP
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