Laser Irradiation for Improving the Wetting of Nanoparticle Gold Inks for Printed Electronics

Digital printing technologies, such as inkjet or aerosol jet, are becoming increasingly interesting for the manufacturing of electronic devices. As a maskless and contactless process, it offers the potential for low-cost deposition of functional materials onto flat, flexible, or 3-D substrates. Common inks used for printed electronics are nanoparticle (NP) metal inks. Silver (Ag) is widely used because of its excellent conductivity, but also gold (Au) inks are of interest for several applications. By using NP inks, it is possible to integrate conductive paths and sensors onto temperature-sensitive substrate materials, such as polymers. Polymers often need a pretreatment, such as a plasma treatment for improving the wetting. Plasma treatment usually changes the wetting behavior of the complete substrate surface. This could be critical for some applications, e.g., fluidic applications, where the original properties of the substrate should be kept. Low-pressure plasma as a vacuum process is also difficult for implementation into an existing process. In this article, laser irradiation for local improvement in wetting of an inkjet-printed gold ink on polymer substrates is investigated. The experiments show that laser irradiation is a very promising technique for the modification of polymer surfaces and suitable for inkjet printing NP inks on hydrophobic polymer surfaces. This offers new opportunities for printed electronics, which could be easily integrated into the existing processes.