Wearable strain sensor for human motion detection based on ligand-exchanged gold nanoparticles

A wearable strain sensor consisting thin films of organic ligand-exchanged gold nanoparticles (Au NPs) was fabricated and optimized by tuning particle size, ligand chain length, number of layers and substrate thickness. The thin films of 5 layers of 8-mercaptooctanoic acid-exchanged Au NPs with size of 9 nm deposited on polydimethylsiloxane substrate exhibited the best performance with excellent gauge factor, high sensitivity, and good reproducibility. The sensor was able to monitor human motions induced by finger and wrist movements. In addition to facile fabrication, this prototype version of wearable strain sensor appears to be practically feasible for the detection of minute human motions.