Direct laser writing of 3D microstructures at solid-liquid interfaces by plasmonic bubbles

Abstract

Plasmonic microbubbles produced by laser irradiated gold nanoparticles (GNPs) in various liquids have emerged in numerous innovative applications. The nucleation of these bubbles inherently involves rich phenomena. In this paper, we systematically investigate the physicochemical hydrodynamics of plasmonic bubbles upon irradiation of a continuous wave (CW) laser on a GNP decorated sample surface in ferric nitrate solution. Surprisingly, we observe the direct formation of well-defined micro-domes on the sample surface. This reveals that the nucleation of a plasmonic bubble is associated with the solvothermal decomposition of ferric nitrate in the solution. The plasmonic bubble acts as a template for the deposition of iron oxide nanoparticles. It first forms a rim, then a micro-shell, which eventually becomes a solid micro-dome. Experimental results show that the micro-dome radius Rd exhibits an obvious Rd ∝ t1/3 dependence on time t, which can be well interpreted theoretically. Our findings reveal the rich phenomena associated with plasmonic bubble nucleation in a thermally decomposable solution, paving the way for a plasmonic bubble based approach to fabricating three dimensional microstructures using an ordinary CW laser.