An Acoustic Touch-Motion Button with Haptic Function via an in-Situ Fabricated Elastomeric Lens Atop PMUTs

Ultrasonic smart-button interfaces have emerged as a promising direction for next-generation human-machine interaction, offering compact, highly accurate, and multimodal sensing. Existing ultrasonic interfaces typically require additional strain sensors for interpreting intent, limiting single-device functionality. Additionally, they lack integrated actuation mechanisms capable of producing the high acoustic pressures required for haptic stimulation. To demonstrate the bidirectional communication ability of ultrasonic interfaces, here we present an integrated manufacturing process and implementation of a variable acoustic touch motion button with haptic function via insitu fabricated elastomeric lens atop piezoelectric micromachined ultrasonic transducers (PMUTs). Three distinctive features have been achieved as compared to the state-of-the-art: (1) direct integration of an elastomeric lens with an acoustic pressure focus point of larger than 3000 Pa for enhanced haptic feedback sensation; (2) pressuresensitive recognitions with variable levels of touch sensing; and (3) ML (machine learning)-based regression with adaptive bidirectional interface for high sensing accuracy. This integration provides a unified hardware-software package where the same PMUT platform supports simultaneous sensing, actuation, and data-driven interpretation of user intent. As such, this work represents a new class of human-machine interface tool with scalable ultrasonic MEMS hardware and intelligent software for touch sensing-sensation applications in handheld device buttons, including cell phones.