Optical fingerprint sensors could be the future.

Next-generation fingerprint sensors won't be tied to specific buttons, nor will they require cutouts that take up precious space on the phone. Companies like Synaptics now have fingerprint sensor solutions that can be embedded under a phone or tablet's display glass, "capable of high-resolution scanning through 1mm of full cover glass and enables clean, button-free industrial designs," the company said in a press release.

That is good, because while many popular Android phones like the Galaxy S7 incorporate a fingerprint sensor into a traditional home button, most Android phones use on-screen navigation, and are forced to find other places to embed biometrics.

The Synaptics FS9100 promises to make fingerprint sensors more water resistant and less prone to degradation over time, and for manufacturers, easier to implement. The main takeaway here is that Synaptics' solution is optical, not capacitive, which doesn't require thinning of the surface glass to improve recognition:

Under cover glass biometrics eliminates button cut-outs and glass thinning processes required by capacitive under-glass sensors, leading to glass yield improvements.

Optical sensors have traditionally been less popular than capacitive ones because they require light to function, and because they aren't typically able to take a 3D reading of a digit. Synaptics claims that these issues have been overcome with this latest generation, and that the FS9100 is even able to accurately read fingerprints through 2.5D glass, which is increasingly common on devices like the Galaxy series.

Could this be the sensor found in the Galaxy S8 Synaptics says that mass shipments will begin in the second quarter of next year, so it's entirely possible.