Within biomedical optical imaging and ultrasonic diagnostics, photoacoustic imaging combines optical contrast with ultrasonic penetration depth, serving as a non-invasive tool for detecting microvascular networks and early-stage pathology. However, during signal detection, high-frequency ultrasonic waves traversing from biological tissue into detectors encounter severe acoustic impedance mismatches, causing reflection and signal loss at boundaries. Engineering biocompatible aerogels with acoustic impedance gradient matching capabilities as coupling layers enhances photoacoustic signal-to-noise ratios.

Acoustic impedance is the product of density and acoustic wave velocity. Because aerogels possess low densities and microscopic network structures, their acoustic impedances can be tuned to intermediate values between biological soft tissue and transducer materials. When biocompatible aerogels are positioned at probe tips, their three-dimensional frameworks act as buffering media. Through pore-wall elasticity and viscous acoustic damping, they transform sharp acoustic propagation interfaces into continuous acoustic impedance transitions. This impedance gradient matching suppresses ultrasonic reflection echoes, raising photoacoustic signal transmission efficiencies.

Furthermore, biocompatible aerogels can incorporate photothermal nanoparticles to generate instantaneous thermoelastic expansion upon laser pulse excitation, emitting high-intensity broadband photoacoustic signals. Integrating photoacoustic signal generation with reflection-suppressing acoustic matching layers improves spatial resolution and sensitivity. Regulating elastic moduli and porosity profiles enables the fabrication of broadband acoustic coupling materials for biomedical imaging.