New Delhi, Sept. 19 -- Apple unveiled its first foldable smartphone, the iPhone Duo, on September 9, with the device set to go on sale from October 23, and Hardware Engineering Vice President Tom Marieb has now shared details about the engineering behind its hinge, display and durability in an interview with TechRadar.

Marieb said Apple put extensive engineering effort into fine-tuning the hinge's torque profile to give it a sturdy, premium feel when opened and closed. He explained that the company modified several mechanical properties of the hinge to achieve the intended experience.

"We really worked on the torque profile very heavily, and that means changing a lot of the mechanical properties of the hinge to have it feel solid, like ...