Quantum tunnelling composite is a fl exible polymer that exhibits extraordinary electrical properties. In its normal state it is a perfect insulator, but when compressed it becomes a more or less perfect conductor and able to pass very high currents. Polymers loaded with carbon are, at best, only partially conductive. In QTC, the change from non-conductor to conductor is dramatic, and a tiny piece measuring 4mm square and 1.5mm thick can pass a current of up to 10 amps when squeezed!

Instead of carbon, QTC contains tiny metal particles, but it does NOT work by percolation. Instead, electrons ‘pass’ through the insulation by a process called quantum tunnelling – hence the name of the material. To explain this effect, we have to appeal to quantum theory and think of the electrons as waves. In classical physics, the electrons cannot pass through an insulation barrier, but according to quantum theory a wave can – and this is what happens in QTC. To some extent we have to suspend belief, because the world seen through quantum theory appears so much at odds with its common sense counterpart. (Another way of describing the quantum tunnelling effect is to say that a probability exists of electrons at point A - one side of the insulation barrier - appearing at point B - the other side. This is all very weird – but demonstrably true.)

QTC pills offer a striking resistance change when deformed by squeezing, pulling or twisting. In practice, QTC can be connected in quite simple ways to create anything from switches to force sensors.