T. Kirscht, M. Marander, F. Liu, S. Jiang
Iowa State University,
Keywords: Additive Manufacturing, Printed Electronics, Nanoinks
Summary:We have invented a platform for producing functional nanoinks to be used in the additive manufacturing of electronic devices that will allow for much finer features to be produced, leading to far more compact and complex designs. Additive manufacturing has seen a rise in popularity in recent years as a technique to fabricate electronic devices. This technology is particularly useful for the on-demand fabrication of components, allowing for rapid prototyping, as well as the fabrication of micro-scale and flexible electronics, which can be used for wearable devices. Currently one of the biggest challenges is to print features with very fine resolution. Printing with higher resolution will enable users to produce more complex and compact devices, as reducing the size of these components has been a continuous goal of manufacturers for many years. Electrohydrodynamic (EHD) printing is a 3D printing technique that is capable of producing patterns with much higher resolutions than the other conventional methods by using an electric field to jet ink onto a substrate. Currently, there are no inks on the market specifically designed to work with EHD printing, and the inks that are commercially available for other printing methods do not work well with this technique. Using a unique synthesis approach, we have developed a platform for producing functional nanoinks that is highly tunable to work with multiple printer systems, including EHD. With our inks, we can print smooth features as small as 3 microns in size, over 10x smaller than commercially available inks can produce using this system or with other techniques. Using this platform, we have developed a highly conductive silver nanoink that achieves over 50% the conductivity of pure metallic silver, which is over twice that of commercial alternatives and will improve the efficiency of printed electronic circuitry. This silver ink is also highly stable with a shelf life of over a year. This can help to improve manufacturing yield and reduce waste from expired products with shorter shelf lives. Our technology also allows us to develop inks based on functional ceramics, something currently not seen on the market. We have developed a dielectric nanoink using barium titanate, which can add further functionality to printed devices. This material can be used to hold charge in capacitors, and it also displays a response to water absorption, making it effective for use in humidity sensors. Additionally, our ink system is the only one to have been adopted by NASA for testing in the EHD printing of devices in space, meeting their requirements for safety, stability, and printing precision. These inks have undergone two zero-gravity flight tests, showing smooth printing in these conditions to meet NASA’s mission requirements. Now the inks are scheduled for more testing to prepare for the launch to the International Space Station as soon as 2024.