Spring 2013 IAB & Research Review
March 6 - 8

Bernhard E. Boser


MEMS AlN Ultrasonic Transducers for Low-Power Gesture Interfaces in Smart Phones

The emergence of hand-held battery powered devices such as smart phones creates a pressing need for novel user interfaces. A wide array of technologies for augmenting presently dominant touch interfaces are under consideration. Touch-free 3D gesture recognition in particular is receiving a lot of attention from industry and academia with a number of different technologies begin pursued, including both active and passive optical 3D cameras and electrical field sensors.

We demonstrate gesture recognition based on ultrasonic transducers. Ultrasonic transduction already finds use in a wide variety of applications including medical imaging, non-destructive sample evaluation, echolocation, and proximity detection. Compared to optical techniques ultrasound has a number of advantages. Independent of ambient illumination, ultrasonic gesture interfaces work both indoors and outdoors or in the dark. Low power dissipation is an enabling advantage of ultrasonic technology: unlike active optical solutions with typical power dissipation of several Watts, ultrasonic transducers operate off micro-Watts, enabling operation even during standby with negligible battery drain. Thanks to the wavelength of sonic waves in air at the millimeter scale, phased array imaging can be employed to scale the device to the chip-scale while still covering a wide field of view and distances up to at least a meter.