Dec 5, 2012
In situ monitoring optimizes flash-light sintering of nanoparticle ink
Printed electronics offer many advantages such as substrate flexibility, low cost and ease of processing. Some of the key components of printed electronics are conducting lines and films. Although conducting polymers could be used for these components, their conductivity and stability are typically inferior to metallic counterparts. Recently, metal-based nanoinks have been introduced to alleviate these shortcomings. However, the nanoinks can be complicated to synthesize, which has cost implications.
Now, reporting their results in the journal Nanotechnology, Hak-Sung Kim, Hyun-Jun Hwang and Wan-Ho Chung based at Hanyang University in South Korea have made a great stride towards the realization of low-cost copper nanoparticle ink. The team has developed a process that enables commercially available Cu/Cu2O nanoparticles to be used in printed electronics.
The production of pure Cu nanoparticles is difficult because they oxidize easily on contact with air. Most commercial Cu nanoparticles are covered with a thin Cu2O shell and cannot be transformed into conducting lines/films through traditional thermal sintering. To alleviate these problems, Hak-Sung Kim’s group has developed a two-step process.
The first step is to functionalize the Cu/Cu2O nanoparticles to induce reduction during sintering. The next step is to use intense pulsed light (IPL) to shorten the sintering time to 20 or so milliseconds. The sintered lines/films exhibit a conductivity that is just a few times lower than the value for bulk copper.
In addition, the researchers optimized the IPL sintering process via in situ monitoring of oxide reduction/sintering phenomena to minimize the re-oxidation phenomena of copper nanoparticles during IPL sintering process (see movie).
The synergistic combination of functionalized Cu nanoparticles and IPL sintering can realize low-cost nanoink and enable instant sintering at room temperature and under ambient conditions for printed electronics.
Back in the lab, the group is working on various other types of nanoparticles and pre-cursor inks for printed electronics and energy harvesting/storage devices in combination with the IPL process.
Additional information can be found in the journal Nanotechnology.
About the author
Dr Hak-Sung Kim received his PhD in mechanical engineering from the Korea Advanced Institute of Science and Technology in South Korea in 2006. He is currently assistant professor in the Mechanical Engineering Department at Hanyang University in South Korea. His current research focuses on reactive IPL processing for material synthesis for flexible printed electronics devices (display, semiconductor and conductive patterns) and energy harvesting/storage applications such as solar cells, fuel cells and supercapacitors. Hyun-Jun Hwang and Wan-Ho Chung are PhD candidates in the School of Mechanical Engineering at Hanyang University in South Korea, under the supervision of Prof. Hak-Sung Kim, PhD. Their research also focuses on printed electronics and its application in display and memory devices using IPL sintering.