Tailoring mechanical and electrical properties of polydimethylsiloxane nanocomposites With graphene and carbon nanotubes for wearable electronics

We explored the use of soft and flexible graphene (Gr)-reinforced polydimethylsiloxane (PDMS; Gr-PDMS) and Gr-carbon nanotube (CNT)-reinforced PDMS (Gr-CNT-PDMS) as nanocomposites (NCPs) in wearable electronic applications and investigated their mechanical and electrical properties. Specifically, we evaluated the mechanical reinforcement of the NCPs by performing Shore scleroscope hardness and machine-washing tests and evaluated their electrical properties by using a four-point probe. The results revealed that as the Gr or CNT concentrations increased, the NCPs' hardness and surface resistance increased and decreased, respectively. Scanning electron microscopy revealed the formation of layered polymeric structures in the Gr-PDMS NCPs, contributing to the increase in hardness and decrease in surface resistance. Furthermore, bending tests revealed that changes in resistance were positively correlated with the Gr concentration. PDMS with low Gr concentrations exhibited no substantial changes in surface resistance after bending tests. However, for PDMS, as the Gr concentration increased (>5 wt.%), the cross-sectional morphology observed after 500 bending cycles differed substantially from that before observed bending tests. Additionally, the influence of one-dimensional (CNT) and two-dimensional (Gr) nanomaterials on the mechanical and electrical properties of the flexible PDMS samples was investigated. The aim of this study is to highlight the importance of considering the properties of different nanomaterials in developing high-performance NCPs for wearable electronics.