Hierarchically Structured Silver Nanosatellite Particles for Highly Conductive Healable Nanocomposites

We report the highly conductive completely reversible electron tunneling-assisted percolation network of silver nanosatellite particles for putty-like moldable and healable nanocomposites.

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Deformable and healable conductive materials have received considerable attention for emerging future electronics, such as artificial human skin, internet of things, and bioelectronics, owing to the recoverability from mechanical/electrical damages. However, their practical applications have been impeded by the low electrical conductivity and irreversible conductivity degradation after breaking/healing cycles.

Here we report the highly conductive completely reversible electron tunneling-assisted percolation network of silver nanosatellite (AgNS) particles for putty-like moldable and healable nanocomposites (Fig. 1). The densely and uniformly distributed hierarchically structured AgNS particles with a bimodal (medium and small) size distribution are generated by the radical and reactive oxygen species-mediated vigorous etching and reduction reaction of silver flakes using tetrahydrofuran peroxide in a healable silicone rubber matrix.

Fig. 1 Hierarchically structured silver nanosatellite particles for the highly conductive, moldable, healable, and stable nanocomposites.

The healing mechanism is based on hydrogen bonding as silicone rubber provides both hydrogen bond donor and acceptor. The average sizes of the medium and small AgNS particles are 164 and 3.7 nm, respectively. The close work function match between silver and silicone rubber enables the electron tunneling between AgNS particles, dramatically increasing the electrical conductivity by ~5 orders of magnitude (maximum: 1.02 × 103 S cm1). The curing process is not involved, and the transport mechanism relies on electron tunneling only without physical coalescence of conductive fillers. This results in a completely reversible reconstruction of the percolation network after healing process, achieving ~100% electrical healing efficiency after 1000 breaking/healing cycles, and stability under water immersion and 6-month exposure to ambient air.

Fig. 2 An emergency electronics repair demonstration is performed by a robot using the conductive healable nanocomposites.

As an application demonstration, the highly conductive putty-like nanocomposites are employed as random-shaped electrical interconnectors, stably operating light-emitting diodes (Fig. 1). An emergency electronics repair demonstration is also performed by a robot using our nanocomposites (Fig. 2). This is useful for accidents at places where humans cannot enter, due to such reasons as the leakage of toxic gas. The highly conductive, moldable, healable, and stable nanocomposites may find applications in improvising and healing electrical parts. Please see our recent publication for more details. Suh, D. et al. Electron tunneling of hierarchically structured silver nanosatellite particles for highly conductive healable nanocomposites. Nature Communications (2020), https://doi.org/10.1038/s41467...

 

 

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Seunghyun Baik

Professor, Sungkyunkwan University

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