The same effect was used to make stickers that lit up when you were receiving a call, with no battery needed! https://hackaday.com/2022/02/26/heres-how-those-b

The same effect was used to make stickers that lit up when you were receiving a call, with no battery needed! https://hackaday.com/2022/02/26/heres-how-those-battery-free-flashing-phone-stickers-worked/ https://hackaday.com/2022/02/26/heres-how-those-battery-free...