Synaptics' fingerprint sensor fits inside the volume rocker
 

Synaptics' latest fingerprint sensor for mobile devices measures only 3.5 mm wide. It's so thin and tiny, it can fit inside a volume rocker switch on the side of your smartphone or tablet. The company is no stranger to developing sensors for various...

http://www.engadget.com/2016/02/17/s...volume-rocker/