The resin within the carbon layers is laced with lithium ions, so that each layer acts like an electrode, causing the positively charged lithium ions to collect in one layer when a voltage is applied, and a current to flow when the sandwich is placed in a circuit.

ECONOMIST: Carbon-composite batteries

When a voltage is applied, the electrostatic force that results either attracts the two mirrors together, or pushes them apart.

ECONOMIST: Displays: The fluttering of tiny pixels | The

When a voltage was applied at the ends of the yarns, these ions moved into the fibres, causing them to expand.

BBC: Nanotube yarns twist like muscles

When a voltage is applied across the coating, the window darkens, allowing less light to enter but still permitting a view.

ECONOMIST: Green homes