Imec demonstrates flat-panel-display-compatible pMUT technology for emerging ultrasound applications

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Imec, the research and innovation centre in nanoelectronics and digital technologies, has used the IEEE International Ultrasonics Symposium to present a piezoelectric Micromachined Ultrasound Transducer (pMUT) array that is compatible with flat-panel-displays (FPD) process technologies.

The array demonstrates acoustic pressures in mid-air above 1kPa, a pressure level that’s relevant for enabling mid-air haptics and directed sound.

Moving from wafer-based to FPD-compatible processes will prepare the pMUT technology for the future integration of mid-air applications, such as vibro-haptics, time-of-flight (3D) sensing or gesture recognition, in a variety of different form factors like smartphones and car dashboards. This technology can be used to create touchless, interactive, screens in automotive and consumer applications, or could be used in gaming.

Ultrasound technology can be used to equip smart systems with haptic feedback, giving the user a sense of touch. In the case of mid-air haptics, ultrasonic waves produce a local pressure field causing the user to ‘feel’ a light sensation without touching the object. Such applications require high-pressures at low ultrasonic frequencies.

Current solutions include, on the one hand, large standard piezoelectric elements that produce relatively high frequencies impeding a precise interaction with the user. On the other hand, small silicon-based micromachined transducer arrays can enable haptic feedback at short distance in a small area only.

Imec’s new FPD-compatible thin-film pMUT technology is said to be inherently more compatible with display manufacturing techniques and, as such, will help to pave the way to applications with much greater area and depth of experience.

Imec’s FPD-compatible thin-film pMUT array now fills the niche for low-frequency, high-pressure devices for large volume mid-air applications. Imec was able to demonstrate peak pressures of ~1.5 kPa in air at resonant frequencies in the range of 200 to 400 kHz, replicating the performance metrics successfully demonstrated mid-air haptic feedback on its Si wafer-based platform.

“We currently offer wafer-level demonstrations of our FPD-technology and prototyping solutions for interested parties. Additionally, we are looking into partnerships for volume manufacturing on large-area panels and plates,” said Erwin Hijzen, Programme Director MEMS Ultrasound at imec.

“The possibility to integrate our pMUT technology into large panels and displays is a key milestone in realisation of our vision on large area sensor surfaces.  We started with ultrasound transducers for in-body imaging and now moved to mid-air applications such as haptics.” added Xavier Rottenberg, Fellow Sensors and Actuators at imec.