A new software is bringing iPhone 6s' Force Touch technology to any smartphone.

Except for the iPhone 6s, no other commercially available device has a force-sensing screen. But engineers at the University of Michigan have sought to change that with a software that offers a new way to bring pressure-sensitive technology to any device.

ForcePhone, partly inspired by a Batman movie, enables users to push a bit harder on a screen button to unlock a menu of additional options, similar to right-clicking with a mouse. The researchers used ultrasonic waves to imitate the effects of 3D touch even without a special screen technology.

"You don't need a special screen or built-in sensors to do this. Now this functionality can be realised on any phone," said Kang Shin, the Kevin and Nancy O'Connor Professor of Computer Science in the UM Department of Electrical Engineering and Computer Science. "We've augmented the user interface without requiring any special built-in sensors. ForcePhone increases the vocabulary between the phone and the user."

Shin created the system with Yu-Chih Tung, a doctoral student in the same department.

"I think we're offering a natural interface, like how you turn a knob," Tung said. "It's the next step forward from a basic touch interface and it can complement other gestured communication channels and voice."

ForcePhone works by borrowing two of a phone's fundamental attributes—its microphone and speaker. The software sets the speaker to emit an inaudible tone at a frequency higher than 18kHz, which is outside the range of human hearing. But the phone's mic can still pick up the vibration caused by the sound.

ForcePhone software Figure 1: ForcePhone, new software developed by University of Michigan engineering researchers, enables the body of any smartphone to sense force. (Image credit: Kelly O'Sullivan)

When a user presses on the screen or squeezes the phone's body, that force changes the tone. The phone's mic can detect that, and the software translates any tone tweaks into commands.

"Having expensive and bulky sensors installed into smartphones can solve every problem we have solved, but the added cost and laborious installation prevent phone manufacturers from doing it," Tung said. "Our sound-based solution can fill this gap, providing the functionality without making any hardware modification. Everything is just software."

The idea of harnessing the phone's microphone and speaker for other purposes is an approach Tung initially picked up from the 2008 Batman movie, "The Dark Knight." In the film, Batman turns all the smartphones in Gotham City into a sonar system as high-frequency audio signals bounce off the city's infrastructure. He uses them to track the Joker.

"I thought it was an interesting idea to turn smartphones into a sonar-based system and felt this could lead to new applications to address challenges faced by smartphone users," Tung said.