Printing Electronic Circuits and Devices via Hybrid Fused Filament Deposition of a TPU/Copper Composite

Printing metals and polymers together to form complex electronic devices is difficult due to the large difference in fusion temperature between those materials. In a previous article, we have introduced a hybrid printing technique based on the fused filament deposition of a copper-polylactic acid composite followed by a step of laser sintering, to produce a conductive, porous copper material. This technology integrates together a conventional fused filament deposition printer and a 10-watt laser diode. The printer is used to deposit layer by layer a composite material containing a polymer matrix, copper, and copper oxide particles. After printing each layer, the laser diode is used to selectively sinter the composite. Under the effect of the laser, the polymer matrix is evaporated, and the copper oxide is reduced, forming a highly conductive, porous copper material.<br/>However, in our precedent experiments, the out-off plane resistivity of this printed porous copper was high, and the applications were restricted to low dimensionality, 2.5D applications. More recently, we have investigated more composite materials and sintering conditions and developed a new TPU based composite. After sintering, this composite presents a resistivity as low a 10−5 Ω x cm in the in-plane direction and 10−4 Ω x cm in the transverse direction. As a result, we can now design and print completely embedded 3D electronic circuits and complex electronic components. We demonstrate these capabilities by making an embedded 3D circuit controlled by capacitive sensors.