High-efficiency photoacoustic transducers based on plasmonic EGaIn liquid metal nanoparticles

Metal nanoparticles hold promising applications in photoacoustic transducers due to their unique plasmonic properties. However, current transducers using conventional noble metal nanoparticles exhibit relatively low photoacoustic conversion efficiency, primarily due to insufficient optical absorption for effective thermal or acoustic energy conversion. This paper proposes the use of nanoparticles derived from the liquid metal gallium-indium eutectic alloy (EGaIn), which demonstrate significantly higher absorption at 1064 nm compared to gold or silver nanoparticles, thereby enhancing photoacoustic conversion efficiency. To stabilize the liquid metal nanoparticles (LMNPs) in a polydimethylsiloxane (PDMS) matrix, 3-mercaptopropyltriethoxysilane (MPTMS) is employed as a surfactant during sonication in a solvent. Furthermore, embedding EGaIn nanoparticles in a cluster form enhances absorption through gap-induced plasmonic effects. Through optimization, a photoacoustic conversion efficiency of 5.1 × 10^-3 is achieved, which is 1-2 orders of magnitude higher than those of transducers using conventional metal materials. This study highlights the potential of liquid metal nanoparticles with plasmonic effects in advancing the development of novel photoacoustic composite materials.