Paper
and textile are two ideal carriers in wearable and printed
electronics because of their flexibility and low price. However, the
porous and fibrous structures restrain their use in printed electronics
because the capillary effect results in ink diffusion. Especially,
conventional metal ink needs to be post-treated at high temperatures
(>150 °C), which is not compatible with paper and textile.
To
address problems involved in ink diffusion and avoid high-temperature
treatment, herein, a new strategy is proposed: screen-printing of
high-viscosity catalytic inks combined with electroless deposition
of metal layers on paper and textile substrates. The ink consists
of Ag nanoparticles, a polydimethylsiloxane (PDMS) prepolymer, and
a curing agent. PDMS as a viscoelastic matrix of catalysts plays key
roles in limiting ink diffusion, enhancing interfacial adhesion between
the substrate and metal layer, keeping metal flexible. As a demonstration,
metal Cu and Ni are printed, respectively. The printed precision (diffusion
< 1% on filter paper) can be controlled by adjusting the Ag content
in the PDMS matrix; interfacial adhesion can be enhanced by ink coating
on substrate microfibers and metal embedding into the PDMS matrix.
In addition, Cu on paper shows extremely low sheet resistance (0.29
mΩ/□), and Cu on nylon shows outstanding foldability
with a resistance of less than five times of initial resistance during
5000 folding cycles.