Scientists in Singapore have invented a cheap, rechargeable and fully biodegradable paper battery that may some day be used to power wearable electronics. It can hold a substantial charge, bending or twisting it does not interrupt power, and larger battery sheets can be cut up and used as individual, smaller batteries. The battery is made by screen printing an ink layer of manganese on one side of a sheet of strengthened paper, and a layer of zinc and conductive carbon on the other. Lithium-ion batteries, the world's standard for rechargeable batteries, cost ten times more to make. The entire paper battery can be safely degraded underground within a month.