3D printable CNT materials Italian researchers
The demand for 3D printable materials with high performance and smart functionalities is increasing since they could move the core of polymeric 3D printing business from rapid prototyping to more sophisticated applications.
A group of Italian researchers has developed photopolymer-based composite Carbon NanoTubes (CNT) materials that can be 3D-printed by Digital Light Processing stereolithography to make functional parts.
As part of a study published on the Science Direct journal, researchers from the Instituto Italiano di Tecnologia Center for Sustainable Future Technologies (IIT-CSFT) in Turin and Politecnico di Torino University teamed up to produce the 3D printer-compatible CNT materials. Annalisa Chiappone and Ignazio Roppolo from IIT-CSFT, with the guidance of Professor Candido Fabrizio Pirri and Professor Marco Sangermano from Politecnico di Torino, began studying new, functional 3D printable materials in 2015.
The demand for 3D printable materials with high performance and smart functionalities is increasing since they could move the core of polymeric 3D printing business from rapid prototyping to more sophisticated applications, such as medicine or electronic goods.
By adding CNTs to an acrylic formulation, the resulting material can be used to print functional parts. The addition of CNTs causes dispersion and stability problems, a large increase of the formulation viscosity and a strong reduction of light penetration depth. Thus, the choice of the most suitable reactive diluent and of the right amount of initiator, was of paramount importance to achieve the printable material.
“We are able to print very simple shapes containing 0.5%wt (weight) of CNT and more complex geometries containing 0.1 or 0.3 wt%,” said Professor Sangermano. “The introduction of CNT in the printed polymer induces an increase of conductivity but the value is still too low to claim to have conductive pieces. The use of more powerful light sources could allow to print composites containing higher amounts of CNT and thus reach higher conductivity values.”
In a bid to avoid viscosity and stability problems linked to the direct addition of the CNT filler, the IIT researchers planned an alternative bottom-up approach. This would see liquid or soluble precursors of the desired nanoparticles added to a light-sensitive mixture in order to obtain the required functionality directly into the printed piece through a post-processing step.
At this stage, silver nitrate was added to a reactive mixture in order to induce the in-situ generation of silver nanoparticles during the UV-post processing of the printed parts, or through a thermal post treatment. This approach enabled the formation of extremely precise polymer-silver structures, with promising electrical properties, meaning it could feasibly become an alternative option for the production of composites 3D structures in the electronics market.
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