It's an advanced material world
Key text
This topic is sponsored by the Australian Research Network for Advanced Materials.
Advanced materials promise to meet the needs of consumers who demand products that are lighter, cheaper, faster and better than ever before.
Advanced materials outperform conventional materials with superior properties such as toughness, hardness, durability and elasticity. They can have novel properties including the ability to memorise shape or sense changes in the environment and respond. The development of advanced materials can even lead to the design of completely new products, including medical implants and computers.
Advanced materials are also amazingly versatile. The product that is used to make windscreen wipers travel smoothly and quietly over the wind screen is also the main ingredient in stain-resistant carpet and upholstery and the non stick surface on frypans - teflon.
The area of advanced materials research is very broad in scope and potential applications. While some advanced materials are already well known, it will take a few more years for others to appear in products. Here, we describe some advanced materials and future technologies they will make possible.
Getting your head around 'smart' materials
Materials scientists divide materials into groups based on what they are made of. These groups include; polymers, metal alloys, ceramics, semiconductors, composites and biomaterials.
A new generation of materials tries to mimic materials and structures in the natural world. Smart materials respond to stimuli in their environment such as temperature, light, magnetic fields or electrical currents.
Related site: Shape memory alloys - an overview
Describes the key properties and applications for shape memory alloys.
(Azom.com)
Advances might include a self-repairing house, antennae that bend towards a signal, liquids that solidify when heated and cans that can be crushed and then regain their original shape under heat - so-called shape memory metals.
Currently, smart materials are made by embedding sensors into pre-existing materials. For example, a pressure- or wear-sensor can be embedded in a car tyre. This can tell the driver when the tyre needs changing and how to drive to reduce tyre wear. New ceramics can sense strain in a building structure and provide early warning of mechanical failure, while others react to changes in temperature or electric current.
Related site: Smart materials
Compares conventional and smart materials, and discusses some applications of smart materials.
(Azom.com)
Ideally, devices made from smart materials would not only provide the information to assess a situation, but also react to it. These devices could then lay down extra adhesive to reinforce a weakened structure or apply an anti-corrosion agent in response to rust, without any human effort.
What to wear
Smart materials in the clothes you wear could also monitor your health, stress levels or other physical needs and respond accordingly. The fibres may become more insulating if you are cold, emit an alarm if you are having a heart attack or provide a read out of your vital signs. Scientists are working on ways to incorporate responsive polymers into fibres and to make them tough enough to cope with daily wear and tear. Skiers from USA and Canada at the 2006 Winter Olympics wore suits that were made from a smart material that instantly hardens upon impact, protecting the wearer from injury.
Getting around - cars, bikes and trains
No matter how you travel, whether it is by car, bike or train chances are an advanced material is involved.
Cars
The car contains many examples of advanced materials, including plastics and advanced alloys. Ceramics are used in engines to reduce wear, oils with additives maintain lubrication, polymers are used in interiors, pipes are made of neoprene and other specialised materials.
Materials scientists have recently developed new high-strength steels for use in car bodies that are 24 per cent lighter and 34 per cent stronger than conventional materials. New magneto rheological fluids can be used in the suspension system of cars to cope with vibration. These liquids are free-flowing until they are placed near a magnetic field and then instantly and reversibly become semi-solid. In the future, bumper bars may be made of an auxetic material which grows fatter when stretched and thinner when compressed.
Bikes
Every part of a bicycle takes advantage of advanced materials including the spokes, tyres, seat and frame. Kevlar tyre tubes are becoming popular because they prevent punctures from thorns, glass, and other sharp objects and can prevent 'pinch' flats when a bicycle tyre thumps into a rock.
The frame of a standard bike is made of chromium steel which is inexpensive and generally rust resistant. Aluminium alloy is becoming more common but, for the bicycle connoisseur, the ultimate frame material is titanium. It is highly corrosion resistant and very light, but is more flexible and resilient than steel.
Future trains
The MagLev (magnetic levitation) train uses superconducting magnets instead of wheels to 'float' on tracks . A large amount of energy is required to cool the superconductors to a temperature where they can operate, and high magnetic fields surround the train, but if these problems can be overcome, it may become a common technology someday.
Looking for inspiration from nature
Have you ever wondered how a flea can jump so high, a limpet stick on a rock so tightly or why mucous is so slimy? Materials scientists, looking for inspiration for new materials think about problems like this all the time (Box 1: What does a material scientist do?).
The idea for nanosprings - minute 'springs' for use in tiny nano-machines - came from an elastic protein called resilin, which helps power insect flight and fleas jumping ability. Resilin has a rubber-like elasticity, changing shape under stress without breaking and recovering to its original form when the stress is removed. CSIRO scientists plan to use resilin for spinal disc implants, as a substitute for heart and blood valves or even to add extra bounce to running shoes.
Other discoveries inspired by nature include pollution-free water-based paints based on the growth and drying of insect wings, and Velcro fasteners which came from observing burrs attach to woollen materials such as socks (Box 2: Designing new materials).
Medical applications of advanced materials
Producing a material that can function effectively inside the human body is quite a challenge. They need to be resistant to corrosion, be compatible with the biological system and have the right kind of strength or flexiblity.
Medical applications of advanced materials may be relatively simple, such as uses in dentistry or to make better contact lenses, or they may be as complicated as producing a functional and lasting hip replacement (Box 3: Advanced materials in the human body).
Materials scientists are working towards implanting man-made devices and materials into the human body to overcome rejection of biological implants by the immune system. Implants include:
- artificial joints including hips, knees, spine, shoulder, finger and toe joints;
- artificial heart valves;
- implanted lenses;
- cardiac stents to hold arteries and veins around the heart open;
- urinary catheters; and
- dialysis tubing for kidney problems.
How well an implanted material can do its job depends on how its surface interacts with the cells of the body - its biocompatibility. Fouling is caused by the accumulation of proteins and cells on surfaces which can lead to bacterial infections and other life threatening complications.
Scientists are developing new coating materials to resist fouling of implants. One coating that shows great promise is a two-part polymer that has a sticky side - based on an adhesive made by mussels to hold on to rocks - and another side that repels cells and proteins.
The age of materials
The future of advanced materials is complex and unpredictable as materials scientists strive to improve present materials and invent new ones to suit our needs. Other areas of research include spintronics, auxetic materials, amphiphilic materials, superconductors and polymers of intrinsic microporosity.
Human beings created the stone, bronze and iron ages. Many believe we are now in the materials age, and it is not hard to understand why. Unless you wear unbleached and naturally-dyed pure cotton, live in a cave with wooden furniture put together with wooden pegs and use clay cooking pots, advanced materials impact your life.
Boxes
1. What does a materials scientist do?
2. Designing new materials
3. Advanced materials in the human body
Related Nova topics
Making light of metals
Putting it together - the science and technology of composite materials
Nanoscience - working small, thinking big
Nanotechnology - taking it to the people
Buckyballs - a new sphere of science
Communicating with light - fibre optics
Piezoelectric sensors and self monitoring planes
Posted June 2006.