What Are Optical Fibres…?Optical fibres carry digital information in the form of LIGHT through a glass or plastic fibre. This is achieved by using the principal of TOTAL INTERNAL REFLECTION to guide the light along the length of the hair-thin fibre.

The light travels through the CORE

The CLADDING reflects light back into the core

The fibre is protected by the outer plastic BUFFER COATING

These fibres are bundled into OPTICAL CABLES which contain hundreds or thousands of fibres

How Do They Work…?The light travels through the core, bouncing off the MIRRORED surface of the CLADDING. The signal does, however, DETERIORATE over a distance due to IMPURITIES in the core that absorb some of the light. The purer the core, the further the light can travel.

A TRANSMITTER encodes the information to be sent through the fibre into light signals. The OPTICAL FIBRE carries the light signals over a distance. An OPTICAL RECEIVER receives and decodes the light signal back into digital information. The signal may need to be boosted by an OPTICAL REGENERATOR if the signal is travelling over a large distance.

What Are They Used For…?Fibre optics are used for… TELECOMMUNICATIONS: transmitting phone signals, Internet connections and cable TV signals; SENSORS: hydrophones, detecting temperature and pressure in conditions unsuitable for other types of sensor and optical gyroscopes; ENDOSCOPES: these consist of an optical fibre and a lens for medical uses such as a non-invasive way of seeing inside of patients, and industrial uses such as seeing inside otherwise hard to see places such as the insides of jet engines; DECORATIVE APPLICATIONS: such as Christmas trees

Composites are engineered materials which contain two or more materials which have differing properties; when combined, these materials give rise to a material with superior physical or chemical properties than either of itsconstituent parts.

Examples of composites are:

•Carbon Fiber •Plywood•Fiber Glass

Carbon Fiber is very good example of a composite material as it shows how carbon fibres in a mesh, suspended in a polymer matrix can give extremely good strength for a very light material. This makes it an excellent material to use when strength in a product is desired but weight needs to be kept to a minimum. Examples of products are things like car body panels, sports equipment and even musical instruments.

Shape memory alloys, or SMA’s, are metals which have two very unique properties, pseudo-elasticity and the shape memory effect. Psuedo-elasticity is where a metal has an almost rubber like flexibility, and its uses include bra underwiring, glasses frames and old mobile phone antennae.

The shape memory effect is a unique ability of shape memory alloys to be severely deformed and then returned to their original shape simply by heating them. The two phases which occur in shape memory alloys when they change state through temperature change are known as ‘Martensite’ and ‘Austenite’. Although a state change occurs, the metal remains a solid, because the molecules remain closely packed when they rearrange. In most shape memory alloys, the temperature only needs to change about 10°C for the state change to occur. The austenite phase is the stronger, high temperature phase, and the martensite phase is the lower temperature, more deformable phase.

The most impressive use of shape memory alloys is in the human body (due to their ‘biocompatibility’). For example when a bone breaks, the metal, in its martensite phase can be wrapped around the bone, and as it heats up, changing shape back into the austenite phase, it exerts pressure pushing the damaged bone sections back together.

What Are Piezo-Electrics…?Certain crystals, such as QUARTZ, produce a VOLTAGE when MECHANICAL STRESS is applied. This effect is also reversible, so if a voltage is applied to the crystal it will cause the crystal to deform.

If a POSITIVE voltage causes the crystal to become STRETCHED, a NEGATIVE voltage will cause it to become COMPRESSED.

+ve -ve

How Does It Work…?The piezoelectric crystal is NEUTRAL overall, but contains separated POSITIVE and NEGATIVE electrical charges, which are symmetrically distributed. When mechanical stress is applied, this disturbs the symmetry of the electrical charges and this causes a VOLTAGE to be produced.

Piezoelectrics can be used as ACTUATORS to turn an electrical input into a mechanical output, or as SENSORS to turn a mechanical input into an electrical output.

What Is It Used For…?Piezo-electricity is used for… SENSORS: such as piezoelectric pickups on electric guitars, electric drum pads and medical ultrasound transducers; ACTUATORS: loudspeakers, inkjet printers and piezoelectric motors; FREQUENCY STANDARD: Quartz clocks and watches use the natural resonant frequency of Quartz to produce electrical pulses to maintain precise time keeping; REDUCTION OF VIBRATIONS: this is a relatively new use of piezoelectrics, and involves crystals detecting vibrations, turning this into an electrical signal, and using that information to create another counter vibration so the two cancel out.

Liquid Crystal Display (LCD):

It is a screen made of monochrome pixels which are relayed to the viewer either by a reflector or back light. These displays are very efficient and popular amongst designers as they require a very small current to operate thus prolonging battery life. Due to this LCD screens have replaced LEDs. LCD screens come in many forms; they are used in TV and PC displays which is a very complex use for them or simply just as displays on calculators and other similar items.

1. Vertical filter film to polarize light.

2. Glass substrate with ITO electrodes- determine light and dark.

3. Twisted nematic liquid crystals.

4. Glass substrate with common electrode film.5. Horizontal filter film to block/allow through light.

6. Reflective surface to send light back to viewer.