Self Healing MaterialsPosted: February 1, 2012
I’ve recently become more obsessed with self healing materials, which I have learned in materials science speak is “autonomous material systems”. I like that fancy title, in one part for it’s scienceness factor, but mostly because it reminds us that materials are complex systems, not a static substance. To get started I’ve included the Wikipedia definition is here (which has an excellent overview of the general research):
Self-healing materials are a class of smart materials that have the structurally incorporated ability to repair damage caused by mechanical usage over time. The inspiration comes from biological systems, which have the ability to heal after being wounded.
Below I’ve collected a variety of case studies and a general overview of some of the principles. If you’re ready to dive into the meat of the science there is a paper available here that really shows off the research.
Autonomous Materials Systems
The best site for an overview of the science as well as mind blowing examples of the materials research is the Autonomous Materials Systems website from the Beckman Institute for Advanced Science and Technology at the University of Illinois at Urbana-Champaign (whew that’s a mouthful).
The materials are incredible. Their research presents three main types of self healing materials;
- Microencapsulated Systems - material containing little capsules filled with a healing agent that bonds when in contact with catalysts also embedded in the material (see diagram below).
- Microvascular Systems – materials filled with capillaries filled with healing agents
- Mechanoresponsive Polymers – modifications made at the chemical level that control how a material responds under strain – simple example is changing colour before failure. I’ll admit I understand this kind the least.
The images of the embedded capsules are amazing, as you can see below:
Self Healing Microelectronics
There are some great movies that show how the above technology could repair scratches and dings in paints – for that perfect auto finish. The real holy grail that appears to be emerging is the development of semiconductors capable to self repairing surprisingly frequent damage. In fact, according to a paper released by Scott R. White and Nancy R. Sottos, up to 80% of semiconductors fail during manufacture. Businessweek has a great article here describing their research, all be it with a cheeky opening line from Jay Leno of all things.
Another variation on the theme is to create a material embedded with capillaries of healing material that can come in contact with embedded catalytic substances to trigger self healing bonding. It appears this process is a little more labour intensive in fabrication, but makes for some amazing diagrams.
Show me the goods!
While there don’t seem to be many tangible products available, beyond self repairing paints, concrete may be one of the first mass produced items. A quick search for self healing concrete reveals many researchers rushing to find an affordable solution with some great results. Read here for an overview of the research behind the impressive photo below.
I’m curious to know how the strain testing works. Is this analogous to an earthquake? Are we looking at the future building material to be sought after in earthquake prone areas?
Self Healing and the Future
Obviously non of the case studies begin to have the level of functionality that compete with natural materials, such as skin and bones, but it does suggest there is a lot happening in this topic. I’m curious what the primary application will be that would be the major success to drive things forward. Self healing car paint is obvious, and reducing the failure rate of semiconductors sounds interesting, but I’m curious how designers would think differently if it was available at the consumer plastics level. Do we need cameras and cell phones to self heal? I’m assuming the real value will lie at the infrastructure level; self healing pipes, linings for electric cables and sewage sound a little boring, but aging infrastructure in cities is a huge issue. Toronto is currently facing an estimated $1.7 billion repair bill for it’s rusted water pipes. That’s an enormous, if unlikely, opportunity for innovation.