ElectronicsElectronics are needed to run the sunglasses, so a small rechargeable battery will be incorporated into the frames.  They take very little energy, however, so even a small battery can run them for a week or more. If the battery does run out, they will still act like normal polarized sunglasses.  The electronic circuits themselves can be fit on a board smaller than a penny, and we’re not done shrinking them yet!