Ultrasound-Induced Mechanoluminescence: From Remote Activation to Emerging Photonic and Biomedical Applications

Abstract Mechanoluminescence (ML) has traditionally been understood as a mechanically induced light emission phenomenon activated by direct contact stimuli such as fracture, deformation, or friction. The emergence of ultrasound (US) as a remote, noncontact mechanical excitation source has fundamentally expanded this paradigm by enabling spatially localized, dynamically controllable, and deep-tissue-accessible activation of luminescent materials. In this framework, US establishes a unique acoustic–mechanical–optical coupling interface that transforms MLs from a material-centric emission effect into a functional photonic transduction platform. Recent advances demonstrate that US-induced ML (US-ML) is rapidly evolving toward biomedical applications, including deep-brain optogenetic neuromodulation, where mechanoluminescent nanotransducers enable implant-free light generation under electronically steerable US fields. Parallel developments in cancer immunotherapy further demonstrate the potential of US-ML nanoplatforms for US-triggered therapeutic release combined with real-time optical feedback. Beyond these demonstrated applications, US-ML may provide opportunities for future bioimaging and biosensing through remotely generated optical signals in deep tissues. Meanwhile, US-ML is increasingly employed for excitation-light-free functional transduction, including ML thermometry and acoustic-pressure-field visualization, in which optical emission encodes local acoustic energy deposition with high spatial fidelity. Emerging studies further reveal that confined ML emission can serve as a localized photon source to drive secondary photochemical reactions, suggesting directions for US-enabled photonic chemistry. Despite recent advances, quantitative applications remain constrained by limited mechanistic understanding, inadequate acoustic calibration, heterogeneous nanoparticle localization, and insufficient in vivo stability. Overcoming these challenges will enable programmable acoustic–photonic platforms for imaging, sensing, photochemistry, and precision medicine.