Towards applicable photoacoustic micro-fluidic pumps: Tunable excitation wavelength and improved stability by fabrication of Ag-Au alloying nanoparticles

Photoacoustic micro-fluidic pumps (PMPs) based on localized surface plasmon resonance (LSPR) of nanoparticles (NPs) can convert photo energy into kinetic energy of fluidic jetting therefore attracted considerable attentions in microfluidics and optofluidics. In this work, PMPs are fabricated using Ag-Au alloy NPs. Through solid-state-dewetting, alloy NPs are prepared of variable component ratios for tunable LSPR absorption between 440 and 530 nm. The relationship between NP morphology and optical properties are studied with the assistant of finite-difference time-domain (FDTD) simulation. Photoacoustic jets are observed through the excitation of both 450 and 532 nm lasers. Noticeably, with 450 nm laser, long lasting jets over 1 h are excited on Ag0.9Au0.1, which sharply contrast to the duration within 1 min on Ag0.2Au0.8 NPs with 532 nm laser, indicating the importance of material selection in performance improvement. Further investigation on jetting stability is performed according to the morphological evolution by laser striking, suggesting the enhanced stability can be related to the increased melting-point and thermal-stability of alloys. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

In this study, photoacoustic micro-fluidic pumps (PMPs) were fabricated using Ag-Au alloy nanoparticles, with tunable LSPR absorption wavelength achieved by adjusting the composition ratios of the nanoparticles. It was observed that the duration of photoacoustic jets excited by 450 nm laser on Ag0.9Au0.1 nanoparticles lasted over 1 hour, contrasting sharply with the jets on Ag0.2Au0.8 nanoparticles under 532 nm laser which lasted less than 1 minute, highlighting the importance of material selection for performance improvement. Further investigation on jetting stability indicated that the enhanced stability could be related to the increased melting-point and thermal stability of the alloys.