Based on CMOS-compatible MEMS, the ultrasound transducers are capable of generating high sound pressure, and provide a flexible frequency design for an optimal balance of distance and sensitivity, enabling a new type of touch-free interfaces. The new transducers could be used to port simple hand movements such as wiping, pulling or tapping, that have become common place through the popularity of smartphones, to screen-less and contactless interfaces.
As the researchers highlight, contactless solutions for man-machine communications are also required in cases where a touch screen is not available or hands and fingers cannot be used. Systems assisting in speech recognition and interpretation in particular are already growing in popularity. However, these systems rely on quiet environments free from external noise disturbances and are sometimes unsuitable for use in public areas. Fraunhofer IPMS researchers are working on an alternative approach to provide non-contact, three-dimensional recording of distance, movement and gesture for communication with robots as well as in surgical areas and household systems.
The micro-chip architecture developed at Fraunhofer IPMS can generate and receive ultrasound up to 300 kHz. Reflected sound waves are analyzed by measuring, for example, how long it took the wave to travel between the sensor system and the reflecting object, or how frequencies shifted due to the Doppler effect. Evaluation of the ultrasound provides a spatial resolution for natural movements and gestures in the sub-centimeter range at distances up to half a meter.
For its MEMS bending actuators, the Fraunhofer IPMS uses the proprietary nano-e-drive (NED) principle, leveraging the high forces of electrostatic fields in nanometre-sized electrode gaps to allow for mechanical movements with displacements in the micrometre range. The chip surface as well as the complete component volume is used for sound generation. The resonance frequency and thus the detection range and spatial resolution can then be defined by the geometry of the NED bending actuators.
Possible fields of applications for ultrasound-based non-contact motion detection include uses in automation, safety and medical technology as well as the automotive and entertainment and household electronics industries. Fraunhofer IPMS will present a first functional demonstrator showing how ultrasound can support gesture recognition at the 2019 Sensor and Test Measurement Fair event in Nürnberg.
Fraunhofer IPMS – www.ipms.fraunhofer.de