Researchers at the University of Pennsylvania in the United States have developed four nanocrystal inks with adjustable properties that allow researchers to tailor their properties for printing useful patterns of transistors. In a research paper entitled "Exploiting the colloidal nanocrystal library to construct electronic devices," co-author Cherie Kagan, professor of engineering and applied sciences at the University of Pennsylvania, and Ji- Hyuk Choi describes how to exploit the diversity of colloidal nanocrystals to design materials, interfaces, and processes to create nanocrystal-based electronic components using solution-based processes. Adjustable colloidal nanocrystalline ink formulation for making printable crystals (Source: University of Pennsylvania) The ink formulation uses tunable colloidal nanocrystals, including metallic silver and semiconducting cadmium selenide nanocrystals, to achieve channel layers of thin-film electrodes and field-effect transistors (FETs) with high conductivity and high mobility, forming high A dielectric constant gate insulating layer of aluminum oxide, and a mixture of indium metal indium nanocrystal and silver nanocrystal that can be integrated on the deposited electrode to passivate and dope cadmium selenide (at low temperature doping diffusion step) Nanocrystalline channel layer. Using a low-temperature multi-step spin-coating process that requires multiple lithography masks and a dedicated surface treatment of nanocrystals, the researchers produced field-effect electricity on a soft plastic sheet with an electromigration of 21.7 cm2v-1s-1 Crystal. The transistor fabrication process utilizes a multi-step spin-on resist coating via a lithography mask and a colloidal nanocrystal ink with a resist removal step (source: University of Pennsylvania) The researchers believe ink formulations can be used with ink jet printers to print transistors and circuits on a wide range of materials, including large, thin flexible substrates or wearable applications. In the future, they think the recipe may also become part of the 3D printing process, adding layers of circuitry to a large number of complex 3D objects. Compile: Susan Hong (Reference text: Low temperature inkjet printable transistors can be stacked, by Julien Happich)