Fast and High-Resolution Ultrasound Pressure Field Mapping Using Luminescent Membranes

Ultrasound is used extensively in medical imaging and therapy, non-destructive testing, flow sensing, underwater range assessment, and acoustic microscopy. To ensure the accuracy of these techniques, detailed knowledge of the acoustic pressure field produced by the ultrasonic transducer is required. This paper proposes a functional polymer membrane loaded with ultrasound-activated luminescent microparticles. The semitransparent membrane makes use of the luminescent properties of BaSi₂O₂N₂:Eu²⁺ to convert ultrasonic pressure into visible light in a fast and straightforward way, through a process termed acoustically produced luminescence (APL). APL is shown to work within a wide range of acoustic frequencies (1–25 MHz) and pressures (50 kPa–4.5 MPa), and enables a quantitative characterization of ultrasound fields with a lateral spatial resolution below 200 µm. At the investigated pressures and frequencies, the light generation mechanism is essentially related to ultrasonic heating rather than mechanical stimulation. These membranes offer effective field mapping possibilities, much faster than conventional time consuming point-by-point hydrophone scanning.