A conventional nanowire-fabrication method generally has an irregularity issue since it mixes chemically synthesized nanowires in a solution and randomly distributes the nanowires onto flexible substrates. As a result, numerous nanofabrication processes have emerged, including ‘master-mould-based’ which enables the fabrication of highly ordered nanowire arrays embedded onto substrates in a simple and cost-effective manner. But, its employment is limited to only some materials due to its chemistry-based nanowire-transfer mechanism which is complex and time consuming. For the successful transfer, it requires that adequate chemicals controlling the chemical interfacial adhesion between the master mold, nanowires, and flexible substrate be present.
Professor Jun-Bo Yoon and his team from the School of Electrical Engineering at KAIST introduced a material-independent mechanical-interlocking-based nanowire-transfer (MINT) method to fabricate ultra long and fully aligned nanowires on a large, flexible substrate in a “highly robust manner”.
This method involves sequentially forming a nanosacrificial layer and nanowires on a nanograting substrate that becomes the master mould for the transfer, then weakening the structure of the nanosacrificial layer through a dry etching process. The nanosacrificial layer very weakly holds the nanowires on the master mould. According to the researchers, when using a flexible substrate material, the nanowires are easily transferred from the master mould to the substrate.
This technology uses common physical vapour deposition and doesn’t rely on nanowire materials, making it easy to fabricate nanowires onto the flexible substrates, the team adds.
Using this technology, KAIST was able to fabricate a variety of metal and metal-oxide nanowires, including gold, platinum, and copper – all perfectly aligned on a flexible substrate. The team also confirmed that it can be applied to creating stable and applicable devices in everyday life by successfully applying it to flexible heaters and gas sensors.
PhD Min-Ho Seo who led this research said: “We have successfully aligned various metals and semiconductor nanowires with excellent physical properties onto flexible substrates and applied them to fabricated devices. As a platform-technology, it will contribute to developing high-performing and stable electronic devices.”