Chewing gum that zaps your tongue with electricity keeps the flavour going forever.

The pain-free device is called “unlimited electric gum”. It uses the piezoelectric effect – a phenomenon where some materials produce electric charge when squeezed. When the “gum” is chewed, it produces a small current, which tricks the tongue into experiencing different tastes .

It currently produces a salty or bitter taste. But the hope is to extend that, since other research has shown that, by varying the pattern …