Featured Research

from universities, journals, and other organizations

Nature shows the way: Self-healing membranes

Date:
September 24, 2011
Source:
Empa
Summary:
The plant liana, whose stabilization rings of woody cells heal spontaneously after suffering damage, serves as a natural example to bionic experts of self-repairing membranes. Such membranes could find use, for example, in rubber dinghies. Researchers have borrowed this trick from nature and developed a polymer foam surface coating with a closed cell construction which not only reduces the pressure loss after the membrane is damaged but also makes the inflatable structure more resistant and giving it a longer operational life.

A membrane made of polyvinyl chloride-polyester (yellowish colour) is punctured with a 2.5-millimeter diameter needle, and at that moment the polyurethane foam (brown) suddenly expands.
Credit: Empa

The plant liana, whose stabilization rings of woody cells heal spontaneously after suffering damage, serves as a natural example to bionic experts of self-repairing membranes. Such membranes could find use, for example, in rubber dinghies. Empa researchers have borrowed this trick from nature and developed a polymer foam surface coating with a closed cell construction which not only reduces the pressure loss after the membrane is damaged but also makes the inflatable structure more resistant and giving it a longer operational life.

The scientists report on this work in the current issue of the Journal of Bionic Engineering.

A hole in an inflatable boat is only a disaster if the air escapes too quickly to reach the safety of land. It's somewhat less dramatic but nonetheless uncomfortable to spend the night on a leaky air mattress. Even in this case, though, you can get some uninterrupted sleep if only the air leaks out slowly enough. In future, self-repairing layers of porous material should ensure that the membranes of inflatable objects are not only water and airtight but also that they can plug up any holes on their own, at least temporarily.

The idea behind this comes from nature. Bionics experts keep on discovering amazing principles of construction which engineers can adopt for countless technical solutions. This is also the case with self-repairing materials. The self-healing process of the pipevine (Aristolochia macrophylla), a liana which grows in the mountain forests of North America, gave the biologists at the University of Freiburg, Germany, a decisive clue. When the lignified cells of the outer supportive tissues which give the plant its bending stiffness are damaged, the plant administers "first aid" to the wound. Parenchymal cells from the underlying base tissue expand suddenly and close the lesion from inside. Only in a later phase does the real healing process kick in and the original tissue grows back.

Self-healing inflatable structures

This principle is now being transferred to materials -- more specifically, to membranes -- in a bionics project sponsored by the German Federal Ministry of Education and Research. As soon as a membrane suffers damage, an additional layer provides "first aid," thanks to its mechanical pre-tensioning, closing the hole until a proper repair can be made. This is analogous to the natural process which occurs in lianas. While researchers from the University of Freiburg under the direction of Olga Speck are busy studying the biological and chemical aspects of the model provided by liana plants, Rolf Luchsinger and Markus Rampf at Empa's Center for Synergetic Structures are working on technical solutions for polymer membranes. Luchsinger's impetus, however, concerns neither inflatable boats nor air mat-tresses but rather load-carrying pneumatic structures for lightweight construction. His tensairity beams serve as elements for quickly erected, lightweight bridges and roofing.

The study's goal is to understand under which conditions a hole plugs itself up if the foam expands on a membrane following damage. Within the scope of his dissertation, Rampf is studying this process with the help of an experimental setup which places a membrane under pneumatic pressure and then punctures it with a nail. The researchers have already achieved successful interim results. A two-component foam of polyurethane and polyester suddenly expands when exposed to the excessive pressure which arises when air rushes out of a hole.

"It works in the lab," notes Luchsinger, "and we're achieving high repair factors." What does this mean in the real world? Take the case of an air mattress with a volume of 200 litres. Given a certain-sized hole, previously it was necessary to pump it up every five minutes; it now holds for eight hours -- enough time to sleep through the night. "We now know enough about the foam that we can enter into discussions with membrane manufacturers about commercializing this technology," according to Luchsinger, when describing the next steps.


Story Source:

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


Journal Reference:

  1. Markus Rampf, Olga Speck, Thomas Speck, Rolf H. Luchsinger. Self-Repairing Membranes for Inflatable Structures Inspired by a Rapid Wound Sealing Process of Climbing Plants. Journal of Bionic Engineering, 2011; 8 (3): 242 DOI: 10.1016/S1672-6529(11)60028-0

Cite This Page:

Empa. "Nature shows the way: Self-healing membranes." ScienceDaily. ScienceDaily, 24 September 2011. <www.sciencedaily.com/releases/2011/09/110923102217.htm>.
Empa. (2011, September 24). Nature shows the way: Self-healing membranes. ScienceDaily. Retrieved July 31, 2014 from www.sciencedaily.com/releases/2011/09/110923102217.htm
Empa. "Nature shows the way: Self-healing membranes." ScienceDaily. www.sciencedaily.com/releases/2011/09/110923102217.htm (accessed July 31, 2014).

Share This




More Matter & Energy News

Thursday, July 31, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Britain Testing Driverless Cars on Roadways

Britain Testing Driverless Cars on Roadways

AP (July 30, 2014) British officials said on Wednesday that driverless cars will be tested on roads in as many as three cities in a trial program set to begin in January. Officials said the tests will last up to three years. (July 30) Video provided by AP
Powered by NewsLook.com
Amid Drought, UCLA Sees Only Water

Amid Drought, UCLA Sees Only Water

AP (July 30, 2014) A ruptured 93-year-old water main left the UCLA campus awash in 8 million gallons of water in the middle of California's worst drought in decades. (July 30) Video provided by AP
Powered by NewsLook.com
Smartphone Powered Paper Plane Debuts at Airshow

Smartphone Powered Paper Plane Debuts at Airshow

AP (July 30, 2014) Smartphone powered paper airplane that was popular on crowdfunding website KickStarter makes its debut at Wisconsin airshow (July 30) Video provided by AP
Powered by NewsLook.com
U.K. To Allow Driverless Cars On Public Roads

U.K. To Allow Driverless Cars On Public Roads

Newsy (July 30, 2014) Driverless cars could soon become a staple on U.K. city streets, as they're set to be introduced to a few cities in 2015. 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