Activity 2 Quantum Tunnelling Composites 3 sessions

Club Leader Notes

Activity 2 Quantum Tunnelling Composites

Resources (for 5 groups)

Activity 2 Quantum Tunnelling Composites

Experiment 1: Using QTC as a simple switch to control a motor or bulb

Activity 2 Quantum Tunnelling Composites

Experiment 2: Using QTC to control the speed of a motor and the brightness of a bulb

Activity 2 Quantum Tunnelling Composites

Experiment 3: More sensitive control of QTC

Activity 2 Quantum Tunnelling Composites

Experiment 4: Using QTC to vary the colour of a tri-colour LED

Activity 2 Quantum Tunnelling Composites

SMART Challenge!

SMART Spark!

Questionnaire

Fact Sheet Quantum Tunnelling Composites

Quantum tunnelling composite, or QTC, is an amazing substance. When in its resting state QTC is

an almost perfect insulator; when pressure is applied, QTC becomes an extremely good, metal-like

conductor of electricity. This strange behaviour is all down to its structure. QTC is a composite

material, containing very small particles of metal embedded in non-conducting binding material

(such as silicone rubber). In its resting state, the metal particles are too far away from each

other to allow electrons to pass between them, so electricity cannot ‘flow’ through it. When

pressure is applied, the metal particles are squeezed closer together, and electricity can now flow

through the QTC. The particles don’t actually touch when they are squeezed – they are still

separated by a minute layer of binding material. But a strange phenomenon called quantum

tunnelling takes place, where electrons ‘tunnel’ through the binding material from one metal

particle to another. This is made easier because the metal particles are spikey.

QTC was discovered by accident!

In 1997, David Lussey, a research engineer in Darlington, was trying to make an adhesive that

would conduct electricity. The substance he made wasn’t a conducting adhesive, but a substance

with unusual electrical properties, now known as QTC. A company called Peratech was set up to

develop the material and its commercial applications. Read about it on

http://www.practicalphysics.org/go/Resources_18.html

Applications

QTC is a versatile switching and sensing medium. Due to its unique electrical properties and

flexible manufacturing possibilities, it has very many potential applications. Here are just a few: