Self-Reducing Silver Ink on Polyurethane Elastomers for the Manufacture of Thin and Highly Stretchable Electrical Circuits

Abstract

Stretchable conductive films were obtained by screen printing and thermal treatment of a homogenous ink comprising a thermally reducible silver formate complex, an acrylate monomer, and a radical initiator. In the curing process, both the filler nanoparticles and the polymer matrix are generated in situ, at temperatures as low as 100 °C. The obtained conductors, consisting of percolated silver nanoparticles embedded in a polymeric matrix, typically show a resistivity of (2–4) × 10–5 Ω·m. When applied on an elastomeric substrate, the composite is stretchable up to 200% with very low R/R 0 values, which is unprecedented for stretchable silver composite inks. Quasi-in situ confocal laser scanning microscopy of the strained samples revealed an initial fracture strain above 40%, which is unusually high for metal–nanoparticle films. The described system was compared to some commercial stretchable screen-printing inks and proved superior with regard to both R/R 0 and resistance to cyclic tensile loading.

An Extensively Adhesive Patch with Multiple Physical Interactions and Chemical Crosslinking as a Wound Dressing and Strain Sensor

“…38−40 In situ formed Ag NPs can avoid the undesirable aggregation and achieve a homogeneous distribution of Ag NPs in the patch. 41,42 Meanwhile, the complexation of disulfide bonds with Ag NPs is helpful to improve and adjust the mechanical properties of the material as required. 43−45 Second, Ag NPs have a broad-spectrum antibacterial property without drug resistance.…”

Materials Engineering for Flexible Metallic Thin Film Applications

“…Inkjet printing represents an attractive technique for patterning, or the “direct writing” of well-defined thin film metal lines with widths down to the micrometer range, thus avoiding masks [ 37 ]. A drawback of such solution-based methods is the use of solvents carrying metallic nanoparticles and binders [ 38 ], or self-reducing methods [ 39 ], which necessitate post-deposition curing to remove solvents and to sinter the nanoparticles. Even then, films are significantly less dense than sputter deposited films, as evidenced by the SEM cross-section of a printed Cu film in Figure 1 d. Consequently, the electrical conductivity of these printed lines is well below that of the corresponding bulk metal [ 40 ].…”

“…As such changes in direction need to overcome energetical barriers, the cracks actually stop propagating. Self-reducing printed Ag films can also have a self-arresting structure created from the inherent porous structure of the films [ 39 ]. A similar method to arrest cracks is to deposit a film with holes using photolithography methods, also known as micro-patterning.…”

Bio-acceptability of wearable sensors: a mechanistic study towards evaluating ionic leaching induced cellular inflammation

“…However, given the inherent biocompatible nature of the carbon-based materials used in these inks, the biocompatibility of carbon inks has been of little or no concern. On the other hand, owing to their high electrical and thermal conductivity, silver inks have widespread applications in the fabrication of wearable sensors and conductive traces in flexible electronics 23 , 24 . The biocompatibility of silver, especially in nanoparticle form, has always remained a concern, significantly limiting its practical usage.…”