Liquid metals such as gallium and its alloys can be printed on various substrates to form electronic circuits. However, up to now there are still few methods for the direct writing of liquid metals on common printed paper. Here, a novel conductive material prepared by adding metal powder to a gallium alloy is introduced. The proposed material exhibits low liquidity, excellent plasticity, significantly enhanced adhesivity to paper substrates, which guarantee the stable and flexible electrical connection. The oxide film wrapping the nickel powder forms a skeleton for additional oxidation products, resulting in superior adhesion to paper. In addition, several paper flexible electronic applications are showcased to demonstrate the practical value and reparability of this material. This work paves the way for the design of a facile method of preparing paper electronics.
Gallium-based
liquid metals are applied in the fabrication of soft
electronics because of their conductivity and flexibility. However,
the large surface tension and weak adhesion of liquid metals limit
the available printing substrates. Recent researches indicate that
amalgamating metal particles can turn liquid metal from fluid into
a paste which has superb electrical conductivity, plasticity, and
strong adhesion to substrates. In this work, a recoverable liquid
metal paste was made by mixing eutectic Ga–In alloy and nonmetallic
SiO2 (quartz) particles (Ga–In–SiO2 paste, called GIS). GIS has excellent conductivity and printable
properties similar to those of previously reported liquid metal pastes.
Furthermore, the bonding between Ga–In alloy and quartz particles
is reversible. In acidic or alkaline solution, Ga–In alloy
can be separated from quartz particles and agglomerated to bulk by
stirring. Moreover, the study of the mechanism of adhesion behavior
suggests that extruding fresh liquid metal droplets to form more oxide
and shearing friction are the critical factors for adhesion. This
work proposed a new liquid metal paste with a reversible rheological
property and promoted the understanding of the working principle of
liquid metal paste.
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