Evolution of nano-junctions in piezoresistive nanostrand composites

When nickel nanostrands (NiNs) are embedded inside of highly flexible silicone, the silicone becomes an extremely piezoresistive sensor capable of measuring a large dynamic range of strains. These sensors experience an increase in conductance of several orders of magnitude when strained to 40% elongation. It has been hypothesized that this effect stems from a net change in average junction distance between the conductive particles when the overall material is strained. The quantum tunneling resistance across these gaps is highly sensitive to junction distance, resulting in the immense piezoresistive effect. In this paper, the average junction distance is monitored using dielectric spectroscopy while the material is strained. By incorporating new barrier height measurements of the base silicone material from a nano-indentation experiment, this experiment validates previous assumptions that, on average, the junctions between NiNs decrease while the sample is strained, instigating the large piezoresistive effect. The nature of the material's response to strain is explored and discussed. (C) 2014 Elsevier Ltd. All rights reserved.