Soft electronics by inkjet printing metal inks on porous substrates

Abstract

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.

Improving durability and electrical performance of flexible printed e-textile conductors via domestic ironing

“…E-textiles research presents a pathway for combining such electronic functionality with textiles of different materials (natural/synthetic or organic/inorganic fibres) [4][5][6], structures (knitted, wovens and nonwovens, calendered, etc) [7][8][9][10][11], and surface finish [12][13][14] while preserving the inherent physical properties that made textiles desirable and versatile materials. So far, the research literature shows that e-textiles are produced by fusing a variety of functional materials such as electrically conductive films [15,16], piezoelectric films [17,18], and thermo/photochromic films [19] with the textiles using any or a combination of (a) rapid prototyping and additive manufacturing processes such as 3D printing [20], ink-jet printing [21], spray-coating [22] and dispenser printing [23] for low-throughput manufacturing, (b) microfabrication processes based on thin-film materials [24], and flexible 1D filaments/yarns [25] and, (c) traditional manufacturing processes within the textile industry (e.g. screen printing [26], lamination [27], weaving [10], sewing and embroidery [28]) for high-throughput manufacturing.…”

Controlling the Polymer Ink’s Rheological Properties to Form Single and Stable Droplet

“…For certain inks, their physical characteristic parameters intricately affect the droplet formation process [26][27][28]. To simplify the influence process, dimensionless parameters were proposed to elucidate the dynamics of droplet formation [29][30][31][32][33][34]. One such parameter is the Weber number (We), representing the ratio of inertial and capillary forces, expressed as follows:…”

Coordinating the pore size of paper substrates and aspect ratio of silver nanowires to improve printed electronics

“…However, porosity of the substrate is not necessarily bad. Porous substrates provide new advantages, such as improving the adhesion of functional films through mechanical interlock, leading to mechanically robust devices [7]. Porous substrates have been reported to enhance the carrier transport efficiency in energy storage materials [5] and reduce the stress concentration in active materials to prevent crack formation and device failure [8].…”

“…To take advantage of these benefits in printed electronics (PE), it is essential to control the wicking of the functional ink into the porous substrate. This challenge can be addressed by optimizing the surface properties of the porous substrate, changing the composition and concentration of the functional ink, or modifying the printing parameters [7]. Here, we explore a different approach to manage the wicking of 1D nanomaterial inks on paper substrates by investigating the relationship between the pore size of paper substrates and the length of silver nanowires (AgNWs).…”