Figure 4. Printed copper patterns. (a) Line patterns for electrical
conductivity measurements. The inset shows a homogeneous and
crack-free print surface. (b) Manually cracked pattern for
investigation of the film thickness after five overprints, revealing a
print thickness of 500 nm per print cycle. The magnification inset of
the fracture surface shows the inner structure of the composite film.
(c) Graph showing the decrease of resistance with larger line width
of the pattern (error bars obtained from five samples at each line
width). The mean electrical conductivity was 1.56 ± 0.48 S cm−1.
(d) Light-emitting diodes directly glued onto printed copper lines.
Norman A Luechinger 2008 Nanotechnology doi: 10.1088/0957-4484/19/44/445201
Institute for Chemical and Bioengineering, Department of Chemistry and Applied Biosciences, ETH Zurich, CH-8093 Zurich, Switzerland
1 Author to whom any correspondence should be addressed
Abstract. Metallic copper nanoparticles were synthesized by a bottom-up approach, and in situ coated with protective shells of graphene in order to get a metal nanopowder of high air stability and chemical inertness. Using an amphiphilic surfactant, a water-based copper nanocolloid could be prepared and successfully printed onto a polymer substrate by conventional ink-jet printing using household printers. The dried printed patterns exhibited strong metallic gloss and an electrical conductivity of >1 S cm-1 without the need for a sintering or densification step. This conductivity currently limits use in electronics to low current application or shielding and decorative effects. The high stability of graphene-coated copper nanoparticles makes them economically a most attractive alternative to silver or gold nanocolloids, and will strongly facilitate the industrial use of metal nanocolloids in consumer goods.
Print publication: Issue 44 (5 November 2008)
Received 11 July 2008, in final form 19 August 2008
Published 26 September 2008