Nanostructure and Mechanism of Metal Deposition by Photo-Thermal Reduction

The laser-induced microbubble technique (LIMBT) has been developed recently for micro-patterning of various materials. In this method, a laser beam is focused on a dispersion of nanoparticles (NPs), leading to the formation of a microbubble due to laser heating. Convection currents around the microbubble carry NPs that are then pinned to the bubble/substrate interface. Moving the focused beam results in migration of the microbubble and the deposition of material at the bubble/substrate contact area.

We have recently found that controlling the construction and destruction of the microbubble, through modulation of the laser, enables the formation of continuous patterns by preventing the microbubble from being pinned to the deposited material.¹ Moreover, we show that a similar mechanism could explain microstructure formation from an ion solution. Photo-thermal reduction leads to formation of NPs that are then pinned to the bubble/substrate interface. By analyzing the nanostructure of the deposits by TEM, we show that the deposition on the substrate is a combination of amorphous and crystalline moieties. This innovative approach can be applicable for producing thin conductive patterns and allow fabrication of electronic devices and sensors.

KEY WORDS: direct laser writing; directed assembly; microbubble; nanoparticle assembly; pattern formation; pinning

1. Armon, N. et al. Continuous Nanoparticle Assembly by a Modulated Photo-Induced Microbubble for Fabrication of Micrometric Conductive Patterns. ACS Appl. Mater. Interfaces 9, 44214–44221 (2017).