Design and fabrication of acoustic lenses for high resolution imaging using optomechanical ultrasound sensors

Imec’s new, ultrasensitive optomechanical ultrasound sensor (OMUS) has opened the way for high resolution acoustic imaging based on the detection of focused ultrasound. This is important for photoacoustic tomography enabling, for instance, the study of brain vascularisation, and breast cancer screening. However, high image resolutions requires sensor arrays with high spatial resolution and therefore a large number of elements and associated driving electronics. To reduce the complexity, acoustic lenses can be used to make more compact and affordable systems that require less sensor elements. This topic will explore in both practice and theory the application of acoustic lenses to arrays of OMUSes for high resolution photoacoustic imaging.

An acoustic lens consists of a material with a different speed of sound from the propagating medium, changing the phase of the sound wave. An ideal material would be easy to form into complex shapes, have a low acoustic attenuation, and have a similar acoustic impedance to that of the propagating medium to minimise acoustic reflections. These acoustic lenses can be 3D-printed or molded into the suitable shape and mounted on a chip of OMUSes.

At the start of your master thesis your first task will be to gain sufficient understanding on both the OMUS and acoustics. You will design an acoustic lens for an existing array of OMUS devices. Thereafter, you can fabricate your designs using a 3D printer and characterise them in an experimental setup. Depending on your interest, it is possible to explore the application and imaging algorithm side as well.