The winter months can bring eye-watering heating bills as you struggle to fight off the cold. Much of that energy is wasted warming up empty air rather than people. A new form of cloth designed to directly heat your skin could provide a solution. Yi Cui of Stanford University in California and his colleagues want to change the way we keep warm. The team has developed a technique for coating textiles in a network of silver nano-wires by dipping cloth in nano-wire “ink”. “The process of making the nano-wire cloth is as simple as dyeing,” says Cui. “The nano-wires stayed on the cloth and formed a conductive network which can reflect human body heat radiation and keep us warm.” Ordinary clothes provide an insulating layer that traps heat against your skin, but the material can still lose heat to the surrounding air. The nano wire cloth acts as a reflecting surface for heat, keeping you warm, but is porous enough to let water through so you don’t feel sweaty. What’s more, because the nano-wire cloth conducts electricity, running a voltage through it heats it up to provide extra warmth. “Just 1 volt can heat up the nanowire cloth to 40 °C,” says Cui. Keeping the current low means there is no danger of burning your skin it’s just like holding a battery.