Wearable devices are small, which means that the size of the components need to be even smaller, battery included. And although they use Bluetooth Low Energy, they still need to be charged frequently. Efficient battery power for wearable devices is a major challenge for designers, so when designing, it’s important to weigh the options.

Thin-film batteries are super skinny. These rechargeable batteries use similar technology as lithium-ion batteries. The benefits of using thin-film batteries are that they are developed as a flat form, thus suitable for thin wearables (e-skin or measurement devices). They’re super lightweight, enable high-energy density for a low price, can be acquired in any size for different purposes, and are 100 percent safe to use (and wear!).

Some disadvantages are that their volume determines their energy capacity, therefore they take up much more area than a coin cell because of their thin form. Plus, they can require more frequent recharge because they are super tiny and skinny for a small wearable device.