Apple has acquired secretive Israeli start-up Q.ai, which makes technology that can read facial expressions, as it pushes ahead with efforts to build wearable devices that can communicate with AI models.

The terms of the deal were not disclosed, but it is thought to be one of Apple’s biggest-ever deals.

One of Q.ai’s backers, GV, formerly Google Ventures, said the deal was the second-largest acquisition in Apple’s history, while the Financial Times cited unnamed people as saying Apple paid close to $2 billion (£1.5bn) for the four-year-old start-up.

Q.ai has filed patents for technology used in headphones or glasses that can read facial micro-movements to allow a user to send silent signals to the device.

Such a system could be used in Apple headphones and other devices to communicate with an AI smart assistant.

Apple’s larges acquisition to date, of Beats in 2014 for $3bn, gave Apple a range of Beats-branded headphones that it sells in addition to its own AirPods products.

It is said to be developing smart glasses to compete with those from Facebook parent Meta Platforms, Google, Snap and others.

Q.ai was founded in 2022 in Tel Aviv by Aviad Maizels, Yonatan Wexler and Avi Barliya, and has kept its technology closely under wraps.

Maizels formerly founded PrimeSense, which Apple bought in 2013 for its 3D technology that formed a key part of Apple’s FaceID login system.