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

Abstract

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.

Ultrasound‐Induced Mechanoluminescence and Optical Thermometry Toward Stimulus‐Responsive Materials with Simultaneous Trigger Response and Read‐Out Functions

“…[ 2 ] Correlations between the level of applied stress and the intensity of luminescence enable a variety of applications, [ 3 , 4 ] for example, in stress sensors, crack detectors, or smart displays. [ 5 , 6 , 7 , 8 , 9 , 10 ] ML induced by ultrasonic excitation (USML) was evaluated for the ability to visualize ultrasonic power distribution, [ 11 , 12 ] but also for security and anticounterfeiting purposes, [ 13 ] or as a photon source in photocatalysis, [ 14 ] photobioreactors, [ 15 ] and optogenetics. [ 16 ] In comparison to conventional ML excited by static or tactile forces, USML offers a remote trigger for luminescent light emission; however, it is currently much less exploited.…”

Ultrasound‐Induced Luminescence from Cr3+‐Doped ZnGa2O4 Glass–Ceramic Composites

“…US heating activates the release of pPL trap states, leading to TSL emission. [22] Cyclic US stimulation data are presented in Figure 4 for rapid cycling (Figure 4e) and slow cycling (Figure 4f ). In both cases, cycles are sufficiently short to avoid any saturation effects: the temperature increase generated on the GCC by each cycle is on the order of 3 K (in comparison to about 30 K in the quasistatic experiments reported in Figure 3).…”

“…[18][19][20][21] Polymer membranes with embedded USL particles were used for fast visualization of the cross-section of ultrasound pressure fields with a spatial resolution below 200 μm for acoustic pressures in the range of 150-4,500 kPa, and frequencies of 1-25 MHz. [22] Such applications could notably benefit from the enhanced mechanical stiffness, thermal stability, and spatial homogeneity offered by fully inorganic ceramics and ceramic composites.…”

Persistent Luminescence in Strontium Aluminate: A Roadmap to a Brighter Future

“…Quite often the persistent luminescence and thermoluminescence of these materials can be adequately modeled using a set of discrete trap depths obeying first-order kinetics. [159][160][161] Additionally there is also a lack of physical grounds behind the use of higher-order kinetics to fit TL glow curves that result from an underlying trap distribution and hence this should be avoided. [162,163] Multiple measurement and analysis protocols have been developed over the years to extract trap depths and frequency factors of the corresponding traps in the material.…”

“…One notable example is the recent discovery that the light emitted by a persistent phosphor under exposure to an ultrasound beam is in fact not due to mechanical stimulation as was first conjectured, [237] but is essentially due to local ultrasonic heating and is hence a special form of thermoluminescence. [160,161]…”