Stabiliser residue inhibits conductivity in 3D-printed electronics

Inks containing metal nanoparticles (MNP) are among the most commonly-used conducive materials for 3D-printed electronics. Ink-jetting layers of MNP materials allow for design flexibility, rapid processing and 3D printing of devices such as sensors, solar panels, LED displays, transistors and smart textiles.

A two-step process is used for inkjet 3D printing of metals: solvent evaporation upon printing (pinning) and subsequent low-temperature consolidation of nanoparticles (sintering). Low temperature is important as the nanoparticles are often co-printed with other functional/structural organic materials that are sensitive to higher temperatures.

However, layers produced by inkjet printing of metal nanoparticles have different electrical conductivity between horizontal and vertical directions. This is known as functional anisotropy and is a long-standing problem for 3D-printed electronics.

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Previously, reduced vertical conductivity was mainly thought to have been caused by shape and physical continuity problems at the interfaces of the constituent nanoparticles at micro and nanoscale.