Printed electronics enable the production of devices with unconventional geometries or mechanical properties, such as flexible, stretchable, and wearable electronics. Within the last several years, 3D printing has been increasingly applied to printed electronics due to its advantages in producing electronics with complex geometries that improve functionality but are too costly or complicated for traditional fabrication techniques. It also enables rapid prototyping, which reduces the time spent designing devices. To accomplish this, specialized inks or filaments are necessary to add functionality to the printed object. Thus, there is a need for a highly conductive 3D printing material that is compatible with consumer-grade tabletop 3D printers, which eliminates the need for expensive inks and printers that are often used with this technique. This poster presents the development of a conductive polymer composite filament containing Ag-coated Cu nanowires. Due to the high aspect ratio of the nanowires, a conductive network could be formed at low volume fractions. However, even a small batch of 3D printing filament requires tens of grams of nanowires. Production of this filament was enabled by the development of a relatively green and fast multigram synthesis of Cu nanowires (4.4 g in 1 hr), and a method to coat the nanowires with Ag within 1 hr. The Cu nanowires were coated with a ~3 nm Ag shell to protect them from oxidation at elevated temperatures and humid conditions, and due to the relatively large diameters of Cu nanowires (~240 nm) produced by this synthesis, a Ag:Cu mol ratio of 0.04 was sufficient. The resulting nanowire-based filament is the first of its kind and has a resistivity of 0.002 Ω cm, &gt;100 times more conductive than commercially-available graphene-based 3D printing filaments. Composite containing 5 vol% of 50-mm-long Cu-Ag nanowires was more conductive than composites containing 22 vol% of 20-mm-long Ag nanowires or 10-mm-wide flakes, indicating that high-aspect ratio Cu-Ag nanowires enable the production of highly conductive composites at relatively low volume fractions. The highly conductive filament can support current densities between 2.5–4.5 x 105 A m-2 depending on the surface-to-volume ratio of the printed trace, and enables the 3D printing of a conductive coil for wireless power transfer.

Multigram synthesis of Cu-Ag nanowires and its application in 3D printing

256th National Meeting (2018)

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