May 13, 2008
Electrical sintering joins up nanoparticles
Applying a DC voltage across a pattern of nanoparticle ink is all it takes to transform the printed structure into a metallic conductor. Developed by scientists in Finland, the sintering method also works in AC mode, which eliminates the need to make physical contact with the ink and allows the user to direct-write features in a single step.
"The key benefit of electrical sintering is that heat generation occurs only in the nanoparticle layer," Mark Allen of VTT Technical Research Centre of Finland told nanotechweb.org. "This opens up the use of substrates with low thermal tolerance and reduces undesirable gas emissions from the substrates."
Using Silverjet DGP-30LT-15C nanoink and a Dimatix Materials Printer (DMP-2831), Allen and his colleagues printed a series of test patterns onto Siena 250G photopaper – a substrate with a thermal limit of just 120 °C. To initiate the sintering process, the researchers applied a DC voltage across the arrangement of silver nanoparticles.
The sample's resistance decreased by more than four orders of magnitude from 150 kΩ to just 4.3 Ω. Looking at the transformation in detail, it appears that the majority of the transition occurs in less than 2 µs.
As well as silver-based nanoinks, the group has found that its method also suits indium tin oxide, which is used widely as a transparent electrode material in display applications. In a roll-to-roll environment, the team's electrical technique could be applied using a sintering cylinder with patterned electrodes.
The researchers presented their work in Nanotechnology.
About the author
James Tyrrell is editor of nanotechweb.org.