NASA has developed a versatile method and associated apparatus for constructing and using a conductive filament in various applications of 3D printing. It uses an attractive polymer formulation, which exhibits low melting temperature even when combined with conductive material, as the printing filament material. It may be used with a commercial 3D printer to generate custom 3D conductive geometries, such as integrated circuitries, electrical connectors, supercapacitors, and flow cell batteries. This invention can be used to create conductive, piezoelectric, or multifunctional materials using three-dimensional printing, with relatively low melt or glass transition temperatures. This invention should be useful wherever such materials are needed, with modest fabrication costs.
Several design challenges have hindered use of conductive materials in commercial 3D printing. One such obstacle is the heating requirements for formation of an object using a 3D printing approach. Conductive materials and additives often have relatively high melting temperatures, usually above 250 °C. That’s above the melt temperatures of plastic filaments that are often extruded by 3D printers, such as Acrylonitrile Butadiene Styrene and Polylactic Acid. A substantial energy input is required, as well as heavy thermal insulation to minimize loss of the heat energy.
Another obstacle is fabrication of the conductive filament itself. This invention from NASA includes the following:
- Polycaprolactone [(C6H10O2)n, referred to as “PCL”], an attractive polymeric material for use in forming a conductive filament. PCL is biodegradable; has a melt temperature of T(melt) = 60 °C; has good resistance to presence of water, oil, solvent, and/or chlorine; and does not produce an abundance of toxins when heated.
- A filament extruder that includes PCL and carbon black powder or graphene, which is conductive and has a relatively low melt temperature.
- A flow cell battery that is 3D printed using vanadium-based material. (d) A honeycomb structure that is formed using 3D printing of silk fibroin and/or chitosan hydrogels into biocompatible polymer networks, which can further be used as a supporting framework in 3D bioprinting.
Potential applications include use in commercial 3D printing, the aerospace industry, and the electrical and electronics industry.