"Wire-Print" as a New Sample Preparation Procedure for Accurate Morphological and Chemical Analysis of Particles and Flakes With Microscopy and Spectroscopy Methods.

The newly developed "wire-print" method is a fast, repeatable and flexible sample preparation procedure aimed at depositing isolated particles or flakes on a substrate for morphological/dimensional analysis, but also for the analysis of the chemical composition. The method was successfully tested on graphene-related 2D materials (GR2M) and a set of representative reference particles with sizes in nano- and micrometer range. Due to their complex morphology and chemistry, the accurate characterization of GR2M is challenging and no standard sample preparation procedure is available. In terms of deposited volume (down to well below 1 nL) and area (down to tens of µm), wire-print is similar to the piezoelectrical-driven inkjet printing, but without applying shearing forces to the suspension. It allows for high-throughput and repeatable deposition of most particulate materials from liquid dispersion as isolated objects onto a substrate. For chemical analysis with Energy-Dispersive X-Ray Spectroscopy (EDS) or X-Ray Photoelectron Spectroscopy (XPS), wire-printing of µm-thick and compact spots is also demonstrated. The very short drying times of tiny volumes of suspension imposed by wire-printing lead to the significant reduction or even disappearance of the typical coffee-ring effect and thus, to a more homogeneous deposition.