Nanoparticle ink can be printed at room temperature

Because the inks developed so far have required annealing, this has limited their application to substrates that can withstand high temperatures. Now, researchers at the National Institute of Materials Science and Okayama University in Japan have developed a nanoparticle ink that can be used at room temperatures. The team says that nanoparticle inks should allow simple low cost manufacture of flexible electronics, but adds the nanoparticles usually used are surrounded by molecules introduced during synthesis to stabilise the particles. These molecules ar removed by annealing to make the ink conductive. Takeo Minari, Masayuki Kanehara and their colleagues say they have solved this challenge by developing nanoparticles surrounded by planar aromatic molecules that allow charge transfer. "This room temperature printing process is a promising method as a core technology for future semiconductor devices," they note. The gold nanoparticles used in the work had a resistivity of around 9 x 10^-6ohm cm – similar to pure gold. The researchers used the nanoparticle ink to print organic thin film transistors on a flexible polymer and a paper substrate at room temperature, producing devices with mobilities of 7.9 and 2.5cm²/Vs for polymer and paper respectively – figures said to be comparable to the performance of InGaZnO based semiconductors. Pictured is an array of organic TFTs inkjet printed on a paper substrate.