Quantum Tunnelling Composite (cord)

This unassuming piece of cord is in fact a sample of quantum tunnelling composite (QTC) - a flexible polymer that exhibits amazing and previously unseen electrical properties. In its standing state it is a perfect insulator, but when squeezed it dramatically changes to become a near-perfect conductor, through which very high currents are able to pass with very little resistance. Scientists have tried to make conductive polymers in the past by loading them with carbon, but these are, at best, only partially conductive. Such polyers also always show some conduction, so they cannot be ‘switched off’ to become an insulator in the same way that QTC can be. QTC works in this way because of the tiny metal (nickel) particles embedded in the polymer. These nickel particles are not smooth; under an electron microscope you can see that their surfaces are covered in microscopic spikes. When the material is squeezed and pressure forces neighbouring particles closer together and a current of electrons can flow between the spikes of neighbouring particles. This process of electrons ‘jumping’ across a gap from one conducting material to another is known as quantum tunnelling, hence the name of the material.

This material was discovered by the then-amateur technologist, David Lussey, allegedly in his kitchen where he was attempting to make a conductive adhesive for use in a security system. To make this conductive adhesive, David mixed metal powders with adhesives in different combinations. One of these began to display strange properties; when two metal plates were glued together they did not conduct, but when he tried to pull the plates apart, they started to conduct.

QTC’s properties lend it to being used in switches and force sensors and it has been used for a number of consumer, medical and industrial applications, including making touch-sensitive fabric panels in suits that allow you to control your mp3 player or similar from your lapel.