It’s an advanced material world

Key text

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.

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:

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

Box 1: What does a material scientist do?

Materials scientists study how things are put together – including their atomic structure, chemical and physical properties – and use this information to create new materials and products. They look at what they require from materials and then alter them to make them better suited to their job.

New materials used to be made on a ‘hit and miss’ basis. It was a bit like a chef experimenting with new spices and cooking techniques without understanding how the ingredients combined to give the final result.

With a deeper understanding of structure and advances in technology, materials scientists have moved far beyond this crude investigation and work on a much more subtle level.

Scientists use computers to improve the speed and accuracy of the experimental process and to reduce the expense involved in finding new materials. In contrast to traditional ‘one-at-a-time’ testing of a material’s properties, computer models allow researchers to manipulate and visualise information and even test ideas in a ‘virtual’ world. They can quickly evaluate how variables such as length of exposure, temperature and composition influence a material’s performance for a specified task. They can then make the material and test it in the ‘real world’.

If you made a list of all the known materials on A4 paper, the pile of pages would be more than half a metre tall. And more are being added to this list every day as scientists modify and develop new materials.

Related sites

• What does a materials person do? (Career Resource Center for Materials Science & Engineering, USA)
• Computational quantum chemistry (Research School of Chemistry, Australian National University)

Box 2: Designing new materials

There are only about 100 different kinds of atoms in the universe. What is created from these atoms depends on how they are put together. The charcoal left after a fire, graphite in a pencil, diamonds in jewellery and carbon nanotubes are all made of carbon atoms put together in different ways.

An understanding and manipulation of the atomic and molecular structure of materials allows scientists to create new materials.

Materials scientists use the four interrelated areas of structure, properties, processing and performance to develop new materials. Structure determines the appearance of a material and its properties. Properties include such things as conductivity, hardness and melting point. Processing relates to how the material is made – things like heating, cooling or applying pressure. Performance is a measure of how well a material functions in its intended use.

The performance of materials can be modified by adding thin films or coatings to surfaces or injecting other elements into the near-surface. An example of this is the razor blades produced by Gillette, which have a surface coating applied to maintain a sharp cutting edge.

An example of the tailoring of advanced materials is that of polymer light-emitting diodes, or polyLEDS. Previously, LEDs were only available in red or green. Any colour in the visible spectrum can now be made by modifying the structure of the polymer – such as poly(p-phenylenevinylene) or poly(fluorene) – or by adding dyes to the polymer to change the colour of light emitted.

Related sites

• Combinatorial materials science (Centre of Advanced European Studies and Research)

• Organic semiconductors in a spin (PhysicsWeb, UK)

  New Scientist

  • Full-colour glow-in-the-dark materials unveiled (13 March 2007)
  • Polymer ‘muscles’ add colour to visual displays (18 August 2006)
  • US and Canadian skiers get smart armour (14 February 2006)

Box 3: Advanced materials in the human body

In the future humans will have the option of many more biomedical materials to help them live with less pain, heal faster, stay healthier and live longer. Recent research breakthroughs in biomaterials are listed below.

New lenses for better eyesight

The ability of the eye to focus on objects changes with age due to stiffening of the lens. A synthetic lens made from a transparent polymer is placed on the cornea of the eye during a simple operation. It is held in place by a surgical ‘glue’ and has a surface coating designed to promote cell growth. The lens can change shape in response to the contraction and relaxation of the muscles of the eye, restoring normal vision.

Moulded artificial bone

A new type of artificial bone is made from polymer and provides mechanical support until new bone grows. It encourages cell growth, can be sterilized and moulded like clay to fill spaces in bones that need to be repaired. It is also sticks to natural bone, hardens in a wet environment and does not damage surrounding tissues.

Building implants for plastic surgery

Implants of silicone or tissue taken from elsewhere in the patient's body have been used by plastic surgeons, but not far away will be implants created from the patient’s own stem cells. Scientists have invented a scaffold or support structure, which is ‘seeded’ with stem cells from bone marrow. The cells are encouraged to grow in the perfect shape for insertion in the body. Because they are made from the patient’s own tissues, they won’t be rejected by the immune system.

Electric powered muscles

New artificial muscles, made of a plastic that bends and contracts like biological muscle, could give future robots enormous dexterity, and also help paralysed humans regain mobility. Artificial muscles could be based on a simple, lightweight strip of highly flexible plastic that bends when electrical voltage is applied to it. Known as electroactive polymers, these strips can be fashioned to activate gripping devices like fingers.

Artificial red blood cells

In a Star Trek like advance, researchers are looking at artificial red blood cells that can be dehydrated, stored for months or even years, and then used for medical emergencies or on space voyages. Artificial red blood cells would eliminate the transfer of diseases such as AIDS or hepatitis through blood transfusions, and could be used to deliver medications to target cells.

Related sites

• Stand by for implantable contact lenses (ONSET, University of New South Wales, Australia)

• Super glue for plastic people (Solve, CSIRO, Australia)

• How to knit yourself some muscles (News in Science, 30 June 2005)

  New Scientist

  • Unbreakable: the tough secrets of nature’s glue (New Scientist, 6 June 2007)

  • How to turn your skin into bone (New Scientist, 2 July 2005)

• AIR: Artificially induced respiration (National Science Teachers Association, USA)

Activities

• Strange Matters, USA
  • Stuff for teachers – students investigate structure, properties, processing and performance aspects of material science.

• Science Net Links, American Association for the Advancement of Science, USA
  • Materials and manufacturing – students identify the properties, limitations and durability of materials and their suitability for different purposes.
  • Recycled materials – students identify materials that can be recycled and possible uses for these materials.
  • Carbon: Structure matters – students explore the molecular structure of matter and how it can affect the physical characteristics of a material.
  • Polymers and people – students learn how advances in science depend on advances in technology and vice versa.
  • What do scientists do? – students report on scientific fields of research to appreciate the diversity of science.

• Polymer Science Learning Center, University of Southern Mississippi, USA
  • Educational resources – provides links to a number of activities and demonstrations about polymers, including ‘Polymers that save lives’ and ‘As the ball bounces’.

• National Aeronautics and Space Administration, USA
  • Absorption and radiation – students investigate the effect of different colors, reflective surfaces and materials on radiant heat absorption and heat radiation.

• Nanosense, USA
  • Size matters – provides an introduction to nanoscience, focusing on concepts related to size and scale, unusual properties of the nanoscale and example applications.

• Oak Ridge National Laboratory, USA
  • A teacher's guide to superconductivity for high school students – students investigate the properties and uses for superconductors using demonstrations and experiments.

• Science upd8, UK
  • Is it terminal for Telfon? – students evaluate evidence surrounding the use of the chemical PFOA and considers a range of viewpoints on the issue including their own.
  • Hard stuff – students learn how scientists made a super-hard material that is cheaper and better at cutting than diamond. You will need to register to access the activity, but it is free.

• University of Cambridge, UK
  • Atomic scale structure of materials – provides an introduction to crystalline, polycrystalline and amorphous solids, and how the atomic-level structure affects the properties of a material.

• Exploring the nanoworld, University of Wisconsin, USA
  • Memory metal – nickel-titanium is used to illustrate how novel properties can occur when alloys are created and how phase changes can occur between two solid phases.
  • Using shape memory metals in simple machines – students learn the connection between memory metal’s atomic structure and its physical characteristics, and identify how memory metal characteristics can be used to solve problems.

• National Physics Laboratory, UK
  • Polymer stretching – this applet helps to visualise the changes going on within a polymer when it is stretched.
  • Semiconductor resistivity – this applet allows you to change temperature, substrate, and doping in a simulated semiconductor, and discover what difference these parameters can have on the conductivity of the material.
  • The bike: Bicycle frame design project – students choose suitable materials to make a bike frame.

• Interviews with Australian Scientists, Australian Academy of Science
  • Transcript of an interview with physical chemist and materials scientist, Professor Frank Caruso. Includes teachers notes and activities.

• Structures and materials, VicPhysics, Australia
  • Copper wire prac – students investigate the behaviour of copper wire under tensile stress.

Further reading

October 2005

• Moving forward together (by Duncan Bond)
  Says there is a need for the suppliers of new materials to work together to curb greenhouse emissions.

• Complex composites (by Chris Edwards)
  Explains how composites may be on their way to matching the versatility of metals.

• Ocean’s seven (by Sally Wilkes)
  Reports on the changes in materials and design specifications for yachts.

• Advancing automotives (by Colin Jackson)
  Looks at the need for new materials in aerospace and automotive areas of production.

• Moving with the times (by Professor Brian Meenan)
  Argues the need to redefine the term 'biocompatibility'.

• Face on (by Richard Curtis)
  Reports on work that has enabled the formation of medical and dental prostheses.

• Reality check (by Sally Wilkes)
  Covers efforts to cut the time needed to design and test medical implants.

Extended brief
Reviews the commercial growth of a technique to make superplastic and its use in the transport sector.

May 2005

• Designed for adversity (by Paul McMillan)
  Reports on the design and testing of materials for applications such as space probes to body implants and sports apparatus.

• Out in the cold (by Ian Salusbury)
  Reports on materials used in conditions of extreme cold.

• Far out – putting new materials in space (by Luke Hutson)
  Looks at the challenges of using nanocomposites in space.

• A design for life (by Richard Bonser)
  Looks at the need to study the ways in which natural materials are produced.

• Go forth and multiply (by Luke Hutson)
  Investigates biological self-replication as inspiration for a self-copying machine.

• Bone in contention (by Ian Salusbury)
  Looks at the field of tissue engineering and biomimetic materials.

• Clever bleeder
• Body fixers (by Pete Wilton)
• Micromachines (by Michelle Knott)

Useful sites

Career Resource Center for Materials Science and Engineering, USA

• What is MSE?
  Provides general information about materials and a brief history of materials science.
  http://www.crc4mse.org/what/Index.html

• Materials in everyday life
  Provides information on the materials used in every day items such as cars, bikes, planes, kitchens and others.
  http://www.crc4mse.org/MEL/Index.html

Strange Matter, UK

• What is materials science?
  The online accompaniment to the Strange Matter exhibition. Provides a definition of materials science and the general categories of materials.
  http://www.strangematterexhibit.com/whatis.html

• Fun stuff!
  Contains interactive activities ‘Zoom’, ‘Materials Smackdown’, ‘The Transformer’ and ‘Change the World Challenge’ to explain the role of structure, properties, processing and performance in material design.
  http://www.strangematterexhibit.com/jump.html

How self-healing spacecraft will work (How Stuff Works, USA)

Describes how spacecraft will be able to mend cracks and faults without human input.
http://science.howstuffworks.com/self-healing-spacecraft.htm/printable

An education outreach manual on tissue engineering (Pittsburgh Tissue Engineering Initiative, USA)

Provides background information on tissue engineering
http://www.ptei.org/docs/TE-Manual-chapter_1.pdf

Nanomaterials: New business from innovation (University of Western Sydney, Australia)

Describes some nanomaterials, how they are made and some potential applications.
http://www.uws.edu.au/download.php?file_id=2284&filename=nano.pdf&mimetype=application/pdf

Australian Broadcasting Corporation

• Is Teflon safe? (Health Matters, 23 February 2006)
  Discusses safety concerns about Teflon and non-stick cookware.
  http://www.abc.net.au/health/thepulse/s1576391.htm
• Brave new world (Features, 4 November 2004)
  Looks at devices created to restore lost function to those with disabilities.
  http://www.abc.net.au/science/features/brave/default.htm
• Medical devices (The Health Report, 6 September 2004)
  Tells a personal story about problems with medical devices and their regulation.
  http://www.abc.net.au/rn/talks/8.30/helthrpt/stories/s1191667.htm
• Innovation in tissue engineering (The Science Show, 5 June 2004)
  Describes tissue engineering for skin grafts and other injuries.
  http://www.abc.net.au/rn/science/ss/stories/s1119444.htm
• Smart fabrics (Catapult)
  Reports on some new smart fabrics.
  http://www.abc.net.au/catapult/indepth/s1435357.htm

Materials Monthly (Centre for Science & Engineering of Materials, Australian National University)

An online magazine that contains articles about Australian materials research.
http://www.anu.edu.au/CSEM/newsletter.php

Research Highlights (Australian National University)

Reports on the research highlights of the Research School of Physical Sciences and Engineering.
http://www.rsphysse.anu.edu.au/admin/php/research_highlights.php

Solve, CSIRO Australia

Contains articles on the latest CSIRO materials research, including:

• Concrete cast in a new light
  Describes a new product for the construction of houses which gives improved strength and insulation over conventional building materials.
  http://www.solve.csiro.au/1105/article11.htm
• Plastic fantastic
  Describes fire-, blast- and acid-resistant geopolymers that have uses in the building and other industries.
  http://www.solve.csiro.au/0505/article10.htm
• Now that’s a smart suit
  Describes a smart fabric that has electronic circuitry made from polymers incorporated into the fabric.
  http://www.solve.csiro.au/0805/article15.htm
• Joint effort proves promising
  Describes a technique that combines a biodegradable polymer and cartilage cells to treat damaged knee joints with a single injection.
  http://www.solve.csiro.au/0206/article2.htm

Glossary

amphiphilic (`loving both'). One end of an amphiphilic molecule is polar and hydrophilic (water loving) and the other is non-polar and hydrophobic (water hating). The hydrophilic ends of the molecule point outwards into the solution and the hydrophobic ends point inwards away from the water, so they tend to self-assemble in water. Amphiphilic materials are already widely used, but research into their use for drug delivery and ultrasound imaging is relatively new.

auxetic materials. Grow fatter when stretched and thinner when compressed – the opposite of a rubber band. Auxetic materials are resistant to impact, so they have possible uses as car bumpers, gaskets in engines, soundproofing and in bullet-proof vests. For more information see Background (Auxetic Materials Network, UK) and Auxetic materials – applications (Azom.com).

biomaterial. A synthetic material used to replace part of a living system or to function in living tissue. A biomaterial is different from a biological material in that it is engineered rather than being naturally produced by a biological system.

ceramics. Are inorganic, non-metallic solids processed or used at high temperatures. A ceramic is made by combining metallic and non-metallic elements. Traditional ceramic products such as clay pots and chinaware are hard, porous and brittle. Modern ceramics are used to create bones and teeth, cutting tools or to conduct electricity. For more information see Advanced ceramics (Azom.com) and About ceramics (The American Ceramic Society).

composites. Are formed by combining two or more materials that have quite different properties. The different materials combine to give the composite unique properties, but within the composite you can easily tell the different materials apart – they do not dissolve or blend into each other. Fibreglass is a composite material made from glass fibres which give it its strength and a flexible polymer resin (matrix) that binds the fibres together. For more information see Putting it together – the science and technology of composite materials (Nova: Science in the news, Australian Academy of Science).

immune system. The cells, tissues and organs that assist the body to resist infection and disease by producing antibodies and/or altered cells that inhibit the multiplication of the infectious agent.

Kevlar. Kevlar is a synthetic polymer fibre and is used when reduced weight, increased strength and long wear life are required. The tensile strength of Kevlar is more than three times greater than that of steel, and its density is less by a factor five, so it is ideal for making very strong, light, flexible structures. It has become a household name, being used for yacht sails, bullet-proof vests and in the aerospace industry.

metal alloys. Metal mixtures with greater strength, hardness or malleability than their component metals. The ratio of each component determines the properties of the alloy. Modern alloys may be created by adding just a few per cent of another metal.

neoprene. The DuPont name for a synthetic rubber fabric made from polymers of chloroprene. While it can only stretch a little, it is very strong. Because of its durability, neoprene is used for many industrial and commercial applications.

polymers. Polymers are large molecules that are made up of many units (monomers) linked together in a chain. There are naturally occurring polymers (eg, starch and DNA) and synthetic polymers (eg, nylon and silicone). More information can be found at The basics – polymer definition and properties (Plastic Resource, USA), Introduction to polymers (Case Western Reserve University, USA) and History of polymers and plastics for teachers (Hands On Plastics, American Plastics Council).

polymers of intrinsic microporosity (PIMs). Are organic polymers that are porous to certain substances and not to others, so they can filter out target molecules. They are useful in industrial processing, medical technologies and in the laboratory, and can supply clean drinking water.

protein. A large molecule composed of a linear sequence of amino acids. This linear sequence is a protein's primary structure. Short sequences within the protein molecule can interact to form regular folds (eg, alpha helix and beta pleated sheet) called the secondary structure. Further folding from interaction between sites in the secondary structure forms the tertiary structure of the protein.

Proteins are essential to the structure and function of cells. They account for more than 50 per cent of the dry weight of most cells, and are involved in most cell processes. Examples of proteins include enzymes, collagen in tendons and ligaments and some hormones. More information can be found at Protein structure and diversity (Molecular Biology Notebook, Rothamsted Research, UK).

semiconductor. Is a material that conducts electricity at a level between an insulator and a conductor. The electrical properties of semiconductors can be controlled by adding small amounts of other atoms or impurities – called doping. Transistors made from semiconductors are used in all electronics including computers, mobile phones, calculators, CD and DVD players. Some semiconductors can also be made to emit light when exposed to an electric field, including diode lasers and light emitting diodes, or LEDs. Silicon is currently the most widely used semiconductor in computer chips and other electronic components. For more information see How semiconductors work (How Stuff Works, USA).

spintronics. Also known as ‘spin-based electronics’, is the science of using electrons to store data. It uses the charge on an electron as well as its ‘spin’ state to store ‘qubits’ of information. Spintronics may lead to a new way of calculating called quantum computing. For more information see Spintronics (Nanotechnology Now) and Spindoctors (PC Magazine, UK).

superconductor. A substance that has no resistance to the flow of an electric current. Superconductors currently require very low temperatures to function. They can be used for energy storage, storing and retrieving digital information, medical imaging machines and friction free transport. For more information see What is superconductivity? (How Stuff Works, USA) and Superconductor information for the beginner (Superconductors.org).

teflon. A polymer of fluorinated ethylene with the chemical name polytetrafluoroethylene (PTFE). It was invented in 1938 and is one of the most slippery substances ever made.