Monolayered Wires of Gold Colloidal Nanoparticles for High-Sensitivity Strain Sensing

High-sensitivity resistive strain gauges based on electron tunneling in assemblies of gold colloidal nanoparticles are fabricated and characterized. The active area of these strain gauges consists in well-defined arrays of parallel, few micrometer wide wires of close-packed 18 nm gold nanoparticles. These nanoparticle wires are obtained by convective self-assembly (CSA) on flexible polyethylene terephtalate substrates, without any lithographic prepatterning. The fine control over the thickness and the width of the nanoparticle wires through the substrate temperature and the meniscus speed during the CSA process allows demonstrating the strong impact of the dimensionality (2D or 3D) of the nanoparticle assembly on the strain gauge sensitivity. Wires made of a single monolayer of nanoparticles turn out to give strain gauges about three times more sensitive than those made of multilayers. This work shows that the simplicity and versatility of convective self-assembly over other alternative methods make this technique very suitable for the reliable and low-cost fabrication of miniaturized, highly sensitive nanoparticle-based strain gauges.