Extrusion-based 3D printing can vertically align 2D nanosheets to improve heat and electricity transport perpendicular to the sheet plane, report researchers at the University of Maryland . Among the many uses, the researchers suggest that it could accelerate the cooling of CPU chips in circuits, by transporting the heat vertically away from the source.
In their recent ACS Nano paper, the researchers led by Liangbing Hu describe a method to obtain 2D materials oriented vertically, and use boron nitride (BN) nanosheets as a proof of concept, proposing a solution to an issue that is a significant challenge and limiting factor in the application of 2D materials.
The new methodology
One of the problems with solution-based self-assembly processes is that they are highly inefficient at generating ordered structures in the vertical orientation. As an alternative technique, Hu and co-workers suggest using a modification to conventional extrusion-based 3D printing methods
Although extrusion-based 3D printing can print in both horizontal and vertical directions and works with many types of materials, it requires the use of ink with the right rheological properties, as well as a means of ensuring the printed BN rods are self-supporting.
To obtain vertical structures of BN nanosheets that are stable after drying, the team of researchers disperses them into a water-based ink binder. Extrusion of ink with 50% BN content from a nozzle 600 μm in diameter gives a self-standing rod that does not collapse. The new methodology allows them to print in air without any further manipulation, and speeds up the printing process for these systems, compared with the layer-by-layer depositing sequence that is commonly used.
A 3D view on 2D materials
The researchers 3D-print vertically aligned BN rods 3-10 mm in height and demonstrate how the adjustable printing conditions (e.g. nozzle diameter, printing pressure) can control the size of the rods and the array. In addition, they embed the arrays into a PDMS matrix and demonstrate an improved thermal conductivity compared with PDMS alone.
The researchers suggest that this method can be extended to other 2D materials to obtain 3D printed structures with higher levels of complexity for different types of applications such as batteries with electrical conductivity extended to a new dimension.
