Accuracy and resolution of Optical Printing

GARGIULO, JULIAN; IANINA L. VIOLI; BRICK, THOMAS; CORTES, EMILIANO; CERROTA, SANTIAGO; CHVÁTAL, LUKÁS; ALBELLA, PABLO; HERRERA, FACUNDO C.; REQUEJO, FELIX G.; MAIER, STEFAN A.; FERNANDO STEFANI

Conferencia; NANOLIGHT; 2018

Optical printing allows the direct assembly of colloidal nanoparticles (NPs), one by one, onto solid surfaces with great flexibility of pattern design and no need of any previous surface patterning. We present a systematic study on the accuracy and the resolution of optical printing applied to Au and Ag NPs. First, the accuracy of optical printing to immobilize single NPs was studied as a function of the laser power and wavelength. Calculated trajectories of the NPs, taking into account the interplay between optical forces and electrostatic forces allowed us to rationalize the experimental results and gain a detailed insight into the mechanism of the printing process. Second, the resolution of optical printing, i.e. the capacity to print two or more NPs at controlled distances is addressed. Before this work, several reports had shown that it was impossible to print two NPs closer together than 200-300 nm, due to a repulsion of unclear nature. Here, we show that the phenomena restricting the optical printing of close by NPs were photothermal forces arising from light absorption by the printed NPs and subsequent local heating. We present several strategies to overcome this obstacle and demonstrate for the first time optical printing of connected nanoparticles. Modeling the experiments considering optical, thermophoretic, and thermo-osmotic forces we obtain a detailed understanding and a clear pathway for the optical printing fabrication of complex nano structures and circuits based on connected colloidal NPs.