Filtration-induced production of conductive/robust Cu films on cellulose paper by low-temperature sintering in air

Abstract

Cellulose paper is an attractive substrate for paper electronics because of its advantages of flexibility, biodegradability, easy incorporation into composites, low cost and eco-friendliness. However, the micrometre-sized pores of cellulose paper make robust/conductive films difficult to deposit onto its surface from metal-nanoparticle-based inks. We developed a Cu-based composite ink to deposit conductive Cu films onto cellulose paper via low-temperature sintering in air. The Cu-based inks consisted of a metallo-organic decomposition ink and formic-acid-treated Cu flakes. The composite ink was heated in air at 100°C for only 15 s to give a conductive Cu film (7 × 10−5 Ω cm) on the cellulose paper. Filtration of the Cu-based composite ink accumulated Cu flakes on the paper, which enabled formation of a sintered Cu film with few defects. A strategy was developed to enhance the bending stability of the sintered Cu films on paper substrates using polyvinylpyrrolidone-modified Cu flakes and amine-modified paper. The resistance of the Cu films increased only 1.3-fold and 1.1-fold after 1000 bending cycles at bending radii of 5 mm and 15 mm, respectively. The results of this study provide an approach to increasing the bending stability of Cu films on cellulose paper.

Surface and Interface Designs in Copper-Based Conductive Inks for Printed/Flexible Electronics

“…In addition, a binder effect was caused by the Cu particles decomposed from the self-reductive Cu complex connected to the Cu flakes. Sakurai et al further modified the mixed paste of the CuF–AmIP complex and Cu flake for the production of highly conductive Cu films on cellulose paper for air atmosphere-sintering [ 140 ]. The Cu flakes were immersed in formic acid to remove the surface oxide layers from the Cu flake.…”

Review of electrically conductive composites and films containing cellulosic fibers or nanocellulose

“…The film resistance of the conductive cellulosic materials was affected by the degree of copper electroplating, and the resistance was at the range between 16.5 and 369.3 Ω/sq. In other work, Cu was deposited on a cellulose surface, yielding a conductive material with high flexibility (Sakurai et al 2018).…”

“…This approach was explained most clearly by Mamunya et al (2002), who showed how metal powders deposited onto larger nonconducting elongated particles can serve as conducting elements as core-shell structures. More typically, conductive materials have been applied to coat cellulosic surfaces by adsorption or particle deposition from solution (Hu et al 2009;Zhou et al 2014;Shi et al 2015;Meulendijks et al 2017;Sakurai et al 2018;Wang et al 2018a). For example, Meulendijks et al (2017) prepared cellulose nanocrystals to which silver particles has been applied to the surface by in-situ precipitation.…”

Printable Thick Copper Conductors from Optically Modulated Multidimensional Particle Mixtures

“…To date, a variety of chemical/physical approaches have been suggested to endow metallic printed features with high conductivity. − Most importantly, from the viewpoint of cost-effectiveness, much recent efforts have been devoted to developing inexpensive Cu conductors. − It has been demonstrated that a critical disadvantage of printable Cu nanoparticles (NPs), namely, unpredictable oxidation behavior during sintering in air, can be overcome by the use of instantaneous optical sintering processes. − One such process, flash-light-sintering (FLS) in a timescale of 10 –3 s, has opened up a new possibility of generating highly functioning Cu conductors with its facile capability for high-throughput production. − The recent efforts of incorporating the chemical moieties triggering a chemical reduction at low temperatures has provided a possibility of generating the Cu conductors by a conventional thermal sintering process in air. In this methodology, the complicated reactions including densification, oxidation, and reduction reactions are associated with each another in a simple thermal annealing process, so that the electrical properties of the resulting conductors are highly dependent on the processing parameters of temperature and time. − …”