Chemical Effect of Halide Ligands on the Electromechanical Properties of Ag Nanocrystal Thin Films for Wearable Sensors

We investigated the chemical effects of halide ligands on the electromechanical properties of Ag nanocrystal (NC) thin films for potential uses in wearable devices and sensors. The halide treatments induced changes in the sizes of sintered NCs, interparticle distances, and microscale surface morphologies. Various characterization techniques and models were used to study the origin of nanoscale and microscale structures, their surface chemistries, and their effects on the electronic and electromechanical properties of the Ag NC thin films. The results indicated that the halide treatments led to changes in the electromechanical gauge factor, which varied from 5 to 600. On the basis of these controllable properties, stable wearable electrodes and sensitive gauge sensors were fabricated. Finally, through all solution processing, we fabricated directly readable wearable circuits and highly sensitive sensors, in which the motion is detected by the intensity of light through the naked eye. We believe that this work will provide fundamental understanding of the chemical effects of nanostructures on electromechanical properties and a pathway to developing a low-cost, high-performance wearable technology.