Forget passwords - you could soon be unlocking your phone by wrinkling your nose or sticking out your tongue

Google has filed a patent that could let users unlock their smartphones and tablets using facial expressions rather than typing in passwords. 

The latest Google Android devices already have a built-in Face Unlock feature that uses facial recognition to unlock their handsets, but this patent would take the technology a step further adding additional 'liveness' features. 

When Google launched Face Unlock in 2011, as part of Android Ice Cream Sandwich, it was criticised by security experts because it could be bypassed by holding static photos up to the phone or tablet's camera.

In the update to Android Jelly Bean in July 2012, Google added a 'liveness' check in an attempt to prevent these static images being used to gain access to devices. 

This meant a user would have to blink while using Face Unlock to prove they were alive.

However, even this could be bypassed using clever photo editing tricks.

According to Google's latest U.S patent, the new system would require users to pull a specific, predeterminded facial expression.

If a patent filed by Google is approved, it could mean users would be able to unlock their smartphones by pulling faces such as frowning, smiling, poking out their tongue, wrinkling their nose, blinking and so on. The technology would compare the facial expression pulled with a previously captured photo and if the expressions matched, the user would be allowed access to their device