Stretchable conductors are essential components of next generation electronic devices that can facilitate integration of human-machine interfaces. However, molecular mechanisms in material deformation and stiffening make the combination of high stretchability and conductivity fundamentally difficult. Best known stretchable conductors partially overcome the dilemma using percolated networks from high aspect ratio nanotubes/nanowires. Various strategies, pre-strained substrates, buckled microwires, three-dimensional microfluidic polymer networks, were also tried to improve parameters. Further improvements can be achieved by using fillers with increased aspect ratio, of all-metallic, or with clever alignments. However, one might expect difficulties withsynthesis/separation, or increased anisotropy/stiffness. Here we demonstrate that excellent stretchable conductors can be made from spherical nanoparticles (NPs) by two methods, layer-by-layer (LBL) assembly and vacuum-assisted flocculation (VAF), despite their minimal aspect ratio. High conductivity and stretchability were observed from both composites and the properties originated from dynamic self-organization of NPs under stress. Modified percolation theory to incorporate the self-assembly behavior of spherical fillers gave excellent match with experimental data. The self-assembly processes and highly efficient charge transport make NP composites similar to liquid metals. They represent a new approach to nanoscale engineering of stretchable conductors and enable electronic tunability of mechanical properties in solid state. Scanning electron microscope, transmittance electron microscope, atomic force microscopy, electrical properties measurement system, dynamic mechanical analysis, small-angle X-ray scattering were performed to analyze properties of nanocomposites.

Stretchable nanoparticle conductors with self-organized conductive pathways

248th National Meeting (2014)

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