Effect of Metal Film Thickness on Strain-Sensing Performance of Crack-Based Stretchable Hybrid Piezoresistive Electrode

In recent decades, many research efforts have been devoted to developing high-performance stretchable strain sensors due to their potential for application in various emerging wearable sensor systems. This work presents a facile yet highly efficient way of modulating the sensing performance of a thin metal film/conductive composite hybrid piezoresistor-based stretchable strain sensor by simply controlling the metal film thickness. The hybrid strain sensor can be simply fabricated by sputtering a thin platinum (Pt) film onto a silver nanowire (AgNW)/dragon skin (DS) composite substrate prepared via a facile embed-and-transfer process in a reproducible manner. The density of the network-shaped mechanical crack induced in the Pt film tended to decrease with increasing the Pt thickness, thereby leading to a higher gauge factor of the sensor. The fabricated hybrid strain sensor also exhibited a large stretchability of 150% owing to its electrical robustness under strain, based on the unique morphology, formed of the network-shaped Pt crack and AgNW percolation network embedded in the DS matrix. Thanks to the balanced strain-sensing performance of the hybrid strain sensor in conjunction with large stretchability, the device was successfully demonstrated as a wearable human-activity monitoring solution that can monitor a wide range of human motions in real time.