Nanoparticle-Based Strain Gauges Fabricated by Convective Self Assembly: Strain Sensitivity and Hysteresis with Respect to Nanoparticle Sizes

The effect of nanoparticle (NP) size on the performance of resistive strain gauges fabricated from gold colloidal NPs is evaluated. The active area of the strain gauges consists of colloidal NPs assembled into multilayered wire arrays on a flexible substrate using Stop&Go convective self-assembly (SG-CSA). The strain sensing in such gauges relies on the exponential variation of tunnel resistance with interparticle gap. The sensitivity of the fabricated strain gauges is found to increase linearly with the size of the gold NPs. A 15 times increase in sensitivity is observed on going from 5 to 97 nm NPs. However, the hysteresis under cycling tests is higher for the most sensitive gauges constructed from larger NPs because of increased disorders in the assemblies of larger NPs, which leads to their irreversible displacement under applied strain. This investigation reveals that the strain gauges derived from 15 nm gold NPs have the best overall performance, with a gauge sensitivity ten times higher than the conventional metal foil gauges at 0.5% strain without undergoing damage under cycling tests.