Soft Electronics by Inkjet Printing Metal Inks on Porous Substrates

Soft electronic devices enable new types of products for an ergonomic interaction of humans with a digital environment. The inkjet (droplet on demand) printing of electrically conductive ink on soft substrates such as paper, textile, and polymers is a promising route for the prototyping and small-scale production of soft electronics that is efficient, cost-saving, and provides a rapid turnaround due to its fully digital workflow. The choice of materials and processing parameters is challenging, however, due to the combined complexity of metal-containing inks, their dynamics during droplet ejection, the active role of the porous substrate, and possible post-deposition steps. This review focuses on recent developments in inkjet printing of metal inks onto soft, porous substrates and their applications. The first section discusses the general principles in the inkjet printing of metal inks, including drop formation and jetting, wetting, and post treatment processes. The second section deals with the effect that the porosity of substrates has on the drying, diffusion, and adhesion of inks. Finally, current challenges and achievements of inkjet-printed, metal-containing inks are discussed.