Influence of the Humidity on Nanoparticle-Based Resistive Strain Gauges

The strong impact of humidity over the performances of gold colloidal nanoparticle (NP)-based resistive strain gauges is quantified and investigated by coupling electro-mechanical and in situ small-angle X-ray scattering measurements. When the relative humidity increases from 0% to 60%, the electrical resistance at rest of the NP -based sensors increases by 40%, and their sensitivity increases by 50%. This is accompanied by a rise of about 1% to 2% in the center-to-center distance between neighboring NPs and by an increase of the compactness of the NP assembly, possible evidence of a reorganization of the NPs. An encapsulation solution, based on alternating polymer and alumina layers, stabilizes the performances of the NP -based strain gauges for strains up to 0.4%. This approach could be extended to other flexible NP-based devices.