These LED lights are powered through the technology of NFC. There is no battery attached to the LED and it only gets power when a NFC signal is put out. The LED is water resistant so you can wash your hands without problems. Because there are tiny circuits on the unit, it would be ideal to be able to smooth it out into acrylics or gel. It is possible to use regular polish on it but it might not come out as well due to the tiny circuits. If you are not familiar with how NFC signal works, a quick Google search can answer all your questions.
Android Users: Almost all new Android phones over the past 2-years have come with NFC hardware built into the phone. To try it out, simply go into your setting and make sure you turn ON the NFC setting. Your phone will typically give off this signal from the back of your phone (usually not the front). It's a directional signal that typically come out from the back side. Every phone outputs the signal from a different area, some from the middle back and some from the bottom back. You just need to play with it to figure it out.
Apple Users: Unfortunately, the only Apple devices that currently has the NFC hardware installed are the iPhone 6 and the iPhone 6+. Even though it does have the hardware installed, Apple does not allow you to play with the NFC setting, meaning it will only go off when Apple allows it. Currently, the only time the iPhone 6/6+ are allowed to transmit the NFC signal is when ApplePay is being used, meaning when you are about to pay at the register using the ApplePay system.
NFC devices: There are many things out in the world that gives off the NFC signal to help power your LED. Most of this will come when you are checking out at a register and certain card readers. The technology gains more traction daily and is being installed all over for different types of uses, allowing your creation to light up more often.