Researchers from Monash University and Swansea University recently reported a new way to create highly concentrated graphene inks that flow well enough for industrial printing, without relying on performance-limiting additives.
The team addressed this challenge by compacting expanded reduced graphite oxide into dense-block reduced graphite oxide, termed DB-rGtO, allowing the formulation of stable dispersions of graphene-derived material at concentrations up to 200 mg·mL−1, while maintaining manageable flowability and deformation resistance.
In fact, the team explained that instead of adding more ingredients to the inks, they chose to change the structure of the graphene itself. The DB-rGtO material forms three-dimensional blocks made up of loosely-packed graphene-like layers, rather than existing as flat, sheet-like flakes. Importantly, parts of these layers remain exposed to the surrounding liquid, allowing the material to interact with solvents in a controlled way.
The 3D structure makes DB-rGtO less prone to irreversible stacking and aggregation, while also reducing the dramatic viscosity increase seen with conventional graphene sheets. As a result, the material can be dispersed at much higher concentrations while still flowing smoothly.
In tests across a range of common printing solvents, DB-rGtO dispersions remained printable at concentrations exceeding 100 milligrams per milliliter—and even up to 200 milligrams per milliliter - without the use of any binders. Using nitrogen-doped expanded reduced graphite oxide as the starting material, this approach enabled single-pass printed films and patterns with conductivities ranging from 5 to 10 Ω·□−1.
The team's findings establish general design rules for formulating concentrated, conductive graphene-based inks with little to no additive, adaptable across various deposition techniques for producing high-resolution, high-fidelity features.
