The rechargeable battery boasts similar electrical characteristics to the lithium ion batteries that power almost every mobile gadget, but it can be applied in layers to almost any surface with a conventional airbrush, said Neelam Singh, a Rice University graduate student who led a team working on the technology for more than a year.

Current lithium ion batteries are almost all variations on the same basic form: an inflexible block with electrodes at one end. Because they cannot easily be shaped, they sometimes restrict designers, particularly when it comes to small gadgets with curved surfaces, but the Rice prototypes could change that.

"Today, we only have a few form factors of batteries, but this battery can be fabricated to fill the space available," said Singh.

The battery is sprayed on in five layers: two current collectors sandwich a cathode, a polymer separator and an anode.

"It was difficult optimizing the components in the form of a paint," said Singh. Initial versions were sensitive to moisture and would peel off, but the addition of a polymer and a heat-sealing step solved this problem.