New and Smart Materials Mr P Mulholland St Joseph’s High School Crossmaglen
New and Smart Materials • Engineers are constantly developing new materials to meet specific requirements. Smart materials are one of these new materials. • A smart material is defined as a material that reacts to an outside stimulus, and once the stimulus has been removed, changes back to its original state. • The stimulus is usually electricity or heat. • Smart materials are being used in products such as food processors and electric drills.
Shape Memory Alloys • A shape memory alloy is a material that can be deformed having been given an outside stimulus and then once it is removed it will return to its original state. • Some react to heat while others react to light. • The most common smart material is Nitinol, an alloy of nickel and titanium. • Nitinol is programmed to maintain a particular length or shape at a certain temperature. If the temperature is raised the material will contract or bend and will remain in that state until the heat is removed and will then return to its original shape. • This cycle can be repeated millions of times.
Shape Memory Alloys • A use for Nitinol includes spectacle frames. The alloy is soft, so the frames are comfortable to wear. But if they get accidentally bent, you can heat the frames using hot water, and they will spring back to their original shape. • http://www.grand-illusions.com/acatalog/Hot_Wire.html • There are some disadvantages. They are relatively expensive to manufacture and are difficult to machine. They are also not as strong as traditional materials such as steel.
Reactive Glass • Reactive glass is a smart glass. • One application of reactive glass is in welding masks. • These have clear glass that remains clear until an arc is struck. • When light from the arc is sensed, the glass turns dark instantly. The welding shield contains electronics and batteries to allow them to operate. • Another application is glass panels that can replace curtains or blinds and give privacy at the touch of a button. • Reactive Glass Video
Photochromic Paint • Photochromic paints contain pigments that change colour according to light conditions. • In one situation they might be one colour, but when sunlight or ultraviolet light falls onto the pigment, there is an immediate change in colour. • When the light source or ultraviolet light is removed the paint returns to its original state. • Examples include security markers or ultraviolet light warning sensors.
Photochromic Paint • Photochromism - colour change caused by light. • Photochromic Paint Video
Quantum Tunnelling Composites • QTC Video • QTC is a new smart material which has a number of applications. • When QTC is in its relaxed state, it is a near perfect electrical insulator but when it is stretched, compressed and twisted it becomes an electrical conductor and allows in some cases, very high currents to pass through it. • The greater the stress that is applied to the material the more it will conduct electricity. • It is being used in products such as power tool switches and robots. It also has potential applications in the textiles industry linking clothes to electronic devices.
Quantum Tunnelling Composites • QTC can be used as a switch, a speed control, or a sensor. Some applications can include: • Controlling speed of a drill by using this in the finger trigger• Embedding QTC in fabrics to make textiles that respond to touch• Long flexible tubes of QTC can be used in the door jam of automobiles to monitor impacts • How QTC works is quite technical as it utilizes a principle of physics called quantum tunneling. The benefit of QTC over other conductive rubbers is that it can carry significantly more current and also there is a more dramatic change in resistance with even a slight change in pressure. This is because its conductivity does not depend on conductive particles in the material actually touching. It can carry up to 10 amps of electricity.
Quantum Tunnelling Composites An example of where QTC fabrics can be woven into clothing. The jacket sleeve features a control panel for the operation of a personal stereo Proposed Use: Inside fabric as a soft switch. A ski jacket has music controls on the sleeve. Proposed Use: Tubing around the frame of doors to sense if the doors are shut. When the door is shut, it will pinch on the QTC cable. Also use a sheet along the inside of body panels to detect impact at any point and activate air bags.